Characterization and testing of landfill leachate - INNO … and treatment of leachate ... (GBB-lab...

Innovationsnetværket for Miljøteknologi

Report

November 2014

INNO-MT - Sustainable handling of

leachate

Characterization and treatment of leachate

landfill_leachate / pjo / 2014-11-06

DHI • Agern Alle 5 • • DK-2970 Hørsholm • Denmark Telephone: +45 4516 9200 • Telefax: +45 4516 9292 • [email protected] • www.dhigroup.com

INNO-MT - Sustainable handling of

leachate

Characterization and treatment of leachate

Prepared for Innovationsnetværket for Miljøteknologi

Represented by Mr/Ms name, title

MBR pilot plant

Project manager Ole Hjelmar

Quality supervisor Per Elberg Jørgensen

Project number 11807382-9

Approval date 30. November 2014

Revision

Classification Open

i

CONTENTS

1 Summary ...................................................................................................................... 1

2 Introduction and objective .......................................................................................... 5

3 Sampling and Chemical analysis of leachate ............................................................ 6 3.1 Sampling ........................................................................................................................................ 6 3.2 Results ......................................................................................................................................... 10 3.3 Discussion .................................................................................................................................... 14 3.3.1 Screening of raw leachate for metals and organic micro pollutants ............................................ 14 3.3.2 The effect of MBR, Active Carbon and Ozone on concentrations of metals and organic

micro pollutants ............................................................................................................................ 14

4 COD-fractionation and inhibition of nitrification – tests in laboratory scale ......... 18 4.1 Chemical analysis of raw leachate............................................................................................... 18 4.2 COD-fractionation ........................................................................................................................ 18 4.3 Long term COD degradation ........................................................................................................ 20 4.4 Inhibition of nitrification ................................................................................................................ 20

5 Aeration and pH-adjustment – test in laboratory scale .......................................... 22 5.1 Aeration ........................................................................................................................................ 22 5.2 pH-adjustment .............................................................................................................................. 23

6 Biological treatment of leachate – test in pilot scale .............................................. 26 6.1 Pilot plant setup............................................................................................................................ 26 6.2 Operation of the biological process.............................................................................................. 26 6.3 Operation of the membrane filters ............................................................................................... 27 6.4 Permeate quality .......................................................................................................................... 28

7 Treatment with activated carbon and ozone – tests in laboratory scale ............... 31 7.1 Activated carbon treatment .......................................................................................................... 31 7.2 Ozone treatment .......................................................................................................................... 33

8 Treatment scenarios and further work .................................................................... 35

9 Conclusion ................................................................................................................. 37

10 References ................................................................................................................. 39

APPENDICES

APPENDIX A – Renosyd, Landfill leachate treatment (GBB-lab and pilot test)

1

1 Summary

Chemical analysis and treatability tests, has been carried out on leachate from Skårup landfill.

The project activities comprised:

Sampling of raw leachate and treated leachate and chemical analysis by external

laboratory, with focus on micro organic pollutants and possible water quality

requirements if treated leachate is to be discharged directly to the recipient.

Laboratory tests by DHI in Hørsholm with focus on COD-fractionation and inhibition of

nitrification

Laboratory tests by Grundfos in Langå with focus of iron removal through aeration and

general precipitation through increase of pH, as pretreatment of leachate prior to

biological treatment in an MBR-system

Pilot test by Grundfos at the pilot test facility in Bjerringbro with focus on the feasibility

of biological treatment of leachate in a BioBooster MBR-system.

Laboratory tests by DHI and Ultra Aqua at the DHI laboratory in Århus, with focus on

activated carbon treatment and ozonation as possible post treatment processes after

biological treatment in an MBR-system.

Chemical analysis of raw leachate From the results of the chemical analysis of raw leachate for traditional wastewater parameters,

metals and organic micro pollutants the following was found:

Concentrations of COD, ammonia-ammonium-N, total phosphorous, total nitrogen, chloride,

sulfate, barium, cobalt, copper, nickel, zinc, PFOS and bisphenol A will exceed the discharge

limit values or the Environmental Quality Standards at least ten times.

The concentrations of suspended solids, arsenic, lead, cadmium, chromium, manganese,

vanadium and the organic micro pollutants DEHP, pyrene, octyl- and nonylphenols in the raw

leachate were also measured in concentrations above the discharge limit values or the

Environmental Quality Standards.

For the metals copper, zinc, lead and cadmium the dissolved concentrations in the raw leachate

can be expected to be up to a factor 3-25 lesser than the measured total concentration

depending on the specific metal, see Table 3-3. This means that the dissolved concentration of

cadmium and lead in the raw leachate probably will not exceed the EQS. For the rest of the

metals the filtration will have lesser or no effect on the concentration and the dissolved

concentrations therefore are still expected to exceed the EQS.

There exists no Environmental Quality Standard for inland surface waters for dioxins and furans.

The measured concentrations of dioxins and furans in the raw leachate (0,352 pg/l) was on the

same level as concentrations measured in the outlet from two large municipal WWTP’s in

Copenhagen (0,097-1,51 pg/l) and concentrations measured in The Sound (0,055-0,377 pg/l) in

2009-2010 expressed as toxic equivalents (WHO(2005)-PCDD/F TEQ) /3/.

The screening of the first sample of the raw leachate for metals and organic micro pollutants

indicated, that concentrations of phenols, hydrocarbons, aromatic hydrocarbons, polyaromatic

hydrocarbons (except pyrene), phthalates (except DEHP), brominated flame retardants and

PCB where generally low and did not exceed the EQS (if it exist).

The concentration of the analyzed components showed generally the same level in all three

samples of raw leachate, except for PFOS/PFOA and bisphenol A, where the concentrations of

2

PFOS and PFOA where approximately 8 times higher in sample 1 compared to sample 2 and 3.

The concentration of bisphenol A where approximately 300 times higher in sample 1 compared

to sample 2 and 3.

COD-fractionation and inhibition of nitrification The COD fractionation tests showed, that for the two samples of raw leachate that was tested,

the content of degradable COD was in the interval of 3-7% of the total content of COD in the

samples. There was no sign that long term contact (up to 5 days) could induce further COD

degradation.

Two different samples tested had very different inhibitory effects on nitrification. The most

concentrated leachate sample showed high inhibition (74 and 35% for 1.5 and 5.2 times dilution

respectively), whereas the less concentrated sample showed low inhibition (19 and 0% for 1.5

and 5.2 times dilution). The concentrated sample had a content of sulphide which may have

contributed significantly to the inhibitory effect.

Iron removal and precipitation by increase of pH The aeration tests were mainly conducted with focus on iron removal. Tests were done on a

concentrated sample of leachate (refered to as contaminated), and on a thinner sample. The

results from the two tests were rather contradictory as the concentration of dissolved iron

increased with a factor of more than 2 for the test with the concentrated sample, and decrease

with a little less than 50% for the test with the thinner sample.

The concentrated and thinner leachate samples mentioned in relation to the aeration tests were

also used for the precipitation tests based on increase of pH. pH was increase by addition of

NaOH in steps from around neutral in the raw leachate to over 12 in the test with the highest

addition. The effect of increasing pH was evaluated by sedimentation in conical glasses. It was

observed that in general the size of the formed flocs increased with the quantity of NaOH added,

and further that the flocs were bigger for tests with the concentrated sample than with thinner

sample. Also, the supernatant of the concentrated sample was darker and more unclear than

the supernatant of the thinner sample.

MBR pilot test The pilot test regarding biological treatment of leachate was carried out by the use of a

BioBooster MBR-pilot plant located at the Grundfos test facility in Bjerringbro. Leachate was

transported from Skårup to Bjerringbro by truck and fed continuously to the pilot plant during the

three week test period. The pilot plant was started with activated sludge from a nearby municipal

WWTP. The initial concentration of MLSS was a little higher than 6 g/l, and no surplus sludge

was wasted during the test period. During the first couple of days of operation the MLSS-

concentration decreased to around 5 g/l, but then remained approximately constant during the

whole test period. The VSS/SS-ratio however showed an almost lineary decrease from around

0.75 to around 0.65. This indicates accumulation of inorganic material while the content of

organic material is decreasing, presumably also the biomass necessary for the biological

treatment. This raises a worry as to the sustainability of long term biological treatment with the

composition of the leachate in question. Nitrification rates measured every week during the test

period showed a slightly increasing tendency for the first two weeks of operation, but then

decreased significantly at the end of the test period. This may have been caused by an inhibitory

effect of the leachate of the last truck load, as it is consistent with the nitrification tests done at

DHI, and on leachate from the same truck load, which showed an inhibition of around 20% if the

leachate was diluted by only 1.5 times.

The membrane filters of the MBR pilot plant was operated at a TMP of 0.5 bar. The initial net

flux was 28 LMH which declined to around 20 LMH after one week operation. Chemically

enhanced back flush could restore the flux by more than 80%. The performance of the filters is

considered acceptable.

3

The permeate quality of the pilot MBR plant was evaluated through frequent analysis of the

traditional parameters COD, ammonia and TP during the test period. In addition to this, inlet raw

leachate and outlet permeate was sampled two times during the test period and the sample

were analyzed for selected micro organic pollutants. It was found that that COD-removal was

low (10-30%). This is consistent with the COD-fractionation tests conducted at DHI which

showed that only 3-7% of the total content of COD in raw leachate was degraded. The

somewhat higher COD-removal observed in the pilot test could be due to adsorption of COD to

the activated sludge. The MBR-system showed full nitrification with a concentration of ammonia

in the outlet typically less than 0.5 mg N/l. All ammonia was converted into nitrate so that the

concentration of TN in the inlet and permeate was at the same level. To comply with expected

TN requirements for direct discharge a denitrification process – through addition of external

carbon - must be applied. TP in the effluent was typically in the interval of 5-10 mg/l, which

means that phosphorous removal, e.g. by addition of precipitation chemicals, will have to be

applied in order to comply with effluent demand for discharge directly to the recipient.

The results of the program for chemical analysis indicated that lead, cadmium and chromium is

reduced to below the discharge limit values/EQS for inland surface waters. The concentrations

of barium, arsenic and manganese were also reduced, but the measured concentrations in the

outlet from the MBR treatment were still above the EQS. The concentrations of the organic

micro pollutants PFOS and PFOA were not significantly reduced with the MBR treatment and

would still pose a problem with discharge of MBR treated leachate to inland surface waters.

Activated carbon treatment and ozonation The tests on treatment by activated carbon and ozone, were both done solely with the aim of

evaluating the potential of the two treatment methods, hence “full throttle” test conditions were

applied in both cases. Under the prevailing test conditions activated carbon treatment was

shown to almost completely remove absorbance at 254 nm, thereby indicating an extensive

removal of COD. As for ozone treatment it was shown that under the prevailing test conditions

more than 60% of the absorbance at 254 nm was removed, indicating a similar degree of COD-

removal. From a visual inspection it could be seen that ozonation completely removed the

yellowish colour of the permeate.

The sample of the Activated Carbon filtrated leachate (sample 6) indicates a further reduction of

the concentrations of COD and manganese to below the discharge limit values/EQS as a result

of the Active Carbon filtration. The concentrations of total phosphorous, total nitrogen, cobalt,

copper, nickel, zinc and PFOS were also reduced, but the concentrations were still above the

discharge limit values/EQS.

The sample of Activated Carbon treated leachate (sample 6) shows significantly higher

concentrations of a number of metals compared to the concentrations in the two samples from

the outlet of the Grundfos BioBooster. It concerns aluminium, antimony, arsenic, barium, lead,

molybdenum and vanadium, see Table 3-4. The samples were re-analyzed but with the same

results, and no explanation can be offered.

As expected the sample of MBR and Ozone treated leachate (sample 7) shows no difference in

concentrations for any of the analyzed components compared to the MBR treated leachate

(sample 5) except for PFOS and PFOA (and to some extend bisphenol A). The concentration of

PFOS and PFOA were reduced with a factor 2.6 and 3.4 respectively compared to the MBR

treated leachate. However the Activated Carbon appears to result in a more efficient removal of

PFOS and PFOA with a reduction in the concentration of a factor 31 and 9 respectively.

None of the three conducted tests of treatment technologies resulted in a removal of PFOS

below the EQS of 0.00065 µg/l.

Treatment scenarios and further work The experimental work carried out in this project aimed at a preliminary evaluation of a general

treatment train consisting of:

4

Based on the results of the experimental work, a pre-treatment process based on addition of

caustic seems interesting as considerable of quantities of sludge flocs was formed in the

laboratory experiments. However further work needs to be done with this process especially to

evaluate the removal of specific compounds, and to optimize the caustic dose.

The MBR pilot test showed that the membrane filters could be operated with a good flux and no

unusual or unacceptable fouling/scaling issues. Further to this it was shown that full nitrification

seems possible and that a number of metals can be removed to a relatively high extent by

adsorption to the activated sludge. As expected, a complete removal of suspended solids was

observed and this is a very important feature of the MBR technology as it opens up for an

efficient permeate polishing process. COD removal and sludge production was rather low,

indicating that sustainable biological treatment might be problematic. Further work should focus

on the development of a concept for sustainable operation of the biological stage. One

possibility towards this goal could be to apply ozone treatment to the MBR influent in order to

produce more degradable COD. Addition of external carbon to the biological stage should also

be considered.

Polishing processes based on ozonation and especially activated carbon showed high to very

very high degrees of removal of the three indicator microorganics (PFOS, PFOA and Bisphenol

A). Although the concentrations in the treated permeate was still well above the EQS limit for all

three microorganic substances tested, ozone and especially activated carbon seems to be

promising polishing methods. In this connection it must be remembered that the effluent

discharge requirements for a given leachate treatment plant, would probably be less strict than

the EQS-values, according to the specific discharge conditions taking the dilution factor in to

account. Further work should be done to optimize ozone dose and retention time for activated

carbon treatment and also to look at the removal of a wider range of microorganic substances.

EQS-values for chloride and sulphate in case of discharge to inland surface waters are quit strict

when compared to the concentrations in raw leachate, and none of the tested treatment

processes will remove salts to any considerable degree. As effluent criteria for specific cases

might be less strict, because of the dilution factors and other considerations, it may not be

necessary to include salt removal in the treatment train. However, in cases where removal of

salts is required, reverse osmosis seems to be the only realistic polishing process to apply,

either alone or in combination with other polishing technologies. In addition to a probably higher

treatment cost for RO than for activated carbon or ozonation, RO would generate a concentrate

(10-30% of the influent volume), that must be handled in a cost efficient and sustainable way.

Further work should therefore also include testing of RO-treatment of MBR permeate, and

solutions to the handling of concentrate should be considered.

Pre-treatment

Biological MBR-

treatmentPolishing

RawLeachate

Discharge to recipient

5

2 Introduction and objective

Using the landfill site Waste Centre Skårup at Renosyd i/s in Skanderborg, Denmark as an

example, a pilot project has been carried out under Innovation Network Environmental

Technology (Inno-MT) with the overall objective to create the basis for reducing the consumption

of resources, the environmental impacts and the costs associated with the operation and

aftercare of a landfill site by applying new and innovative solutions for waste water treatment

and landfill management.

The three main goals of the pilot project are:

A. To assess and describe the content and methodology of a decision support tool for short

and long term management of leachate from landfilled waste.

B. To identify suitable combinations of treatment technologies for the leachate through testing

at pilot and laboratory scale.

C. To identify new technological measures and strategies to influence and accelerate those

stabilising processes which in a landfill can contribute to shorten the aftercare period.

The project participants are Renosyd i/s, DHI, Grundfos Biobooster, Dansk Affaldsforening and

UltraAqua.

In the document at hand, project activities related to main goal B are reported.

6

3 Sampling and Chemical analysis of leachate

Sampling and analysis of landfill leachate from Waste Centre Skårup at Renosyd I/S in

Skanderborg, Denmark was carried out with the aim of characterizing the leachate and

assessing the compliance with national and European Environmental Standards for inland

surface waters before and after treatment with MBR, Active Carbon and Ozone.

3.1 Sampling

A schematic view of the treatment and sampling of the landfill leachate is shown in Figure 3-1.

Figure 3-1 Schematic view of treatment and sampling of landfill leachate from Waste Centre Skårup.

All samples were taken in sampling bottles provided by Eurofins Miljø A/S or in 10 liters

annealed glass bottles. Samples were kept cold at +5 °C until mixing and analysis. All chemical

analysis was performed by Eurofins Miljø A/S.

Details about the sampling are shown in Table 3-1.

Sample 1 Raw landfill leachate

from Waste Centre

Skårup (B16.9)


from Waste Centre

Skårup (B16.9)

Inlet to MBR treatment


from Waste Centre

Skårup (B16.9)

Inlet to MBR treatment

Sample 4 Outlet from MBR

treatment

Sample 5 Outlet from MBR

treatment

MBR treatment in

Grundfos

BioBooster

MBR treatment in

Grundfos

BioBooster

Sample 6 Outlet from Activated

Carbon Filter

Activated Carbon

Filter treatment

Ozon treatment

Sample 7 Outlet from Ozon

treatment

7

Table 3-1 Details about samples, sampling period and sampling method.

Sample No.

Sample Sampling period Sampling method

1 Raw landfill leachate from Waste Centre Skårup (B16.9)

From 30.06.14 12:15 To 01.07.14 12:15

Time proportional

2 Raw landfill leachate from Waste Centre Skårup (B16.9) (Inlet to BioBooster)

From 22.08.14 14:00 To 23.08.14 12:00

Flow proportional

3 Raw landfill leachate from Waste Centre Skårup (B16.9) (Inlet to BioBooster)

From 24.08.14 12:00 To 25.08.14 11:00

Flow proportional

4 MBR treated leachate (Outlet from BioBooster)

From 22.08.14 14:00 To 23.08.14 12:00

Flow proportional

5 MBR treated leachate (Outlet from BioBooster)

From 24.08.14 12:00 To 25.08.14 11:00

Flow proportional

6 MBR and AC treated leachate

The AC tests was conducted over app. 8 hours corresponding to about 16 bed volumes

After passage of the AC column the water was collected in a container from which it was distributed to the sample bottles from Eurofins

7 MBR and Ozone treated leachate

The ozone tests was conducted over 20 min.

The ozone experiments were carried out as batch experiments where the sample was fed with ozone in a bubble column. After 20 min the experiment was stopped and the column emptied and the sample distributed into Eurofins sample bottles

The first sample (Sample 1) was taken as a time proportional sample from B16.9 at Waste

Centre Skårup by Eurofins Miljø A/S. The sample was analyzed for a large number of

components including metals, trace elements and micro organic pollutants in order to screen the

leachate for substances in concentrations above the Environmental Quality Standards. The first

sample was used to select the relevant analysis components for the subsequent samplings and

analysis. The results of the chemical analysis of Sample 1 are shown in Table 3-2 together with

the Environmental Quality Standards (EQS) for inland surface waters. Measured concentrations

above the EQS are marked with red. Components selected for the subsequent sampling and

analysis is marked with an “X” in Table 3-2.

Table 3-2 Chemical analysis of leachate from Waste Centre Skårup (Sample 1).

Component Unit Sample 1

Raw leachate EQS

1) Selected for subsequent analysis

pH pH 7,5 6,5-9,0 2)

X

Suspended Solids mg/l 62 25 2)

X

Conductivity mS/m 640 X

Nitrification inhibition (200 ml/l) % <20

COD mg/l 310 30 2)

X

NVOC mg/l 95 X

Inorganic components

Ammonia+ammonium-N, filtered mg/l 140 1 2)

X

Nitrite-nitrate-N, filtered mg/l 0,82

Total nitrogen mg/l 140 1 2)

X

Total phosphorous mg/l 1,3 0,1-0,15 2)

X

Fluoride (F) mg/l 0,082

Chloride, filt mg/l 820 0,5-40 2)

X

Sulfate, filt mg/l 580 40 2)

X

Hydrogen carbonate mg/l 2100 X

Metals

8

Aluminium (Al) µg/l 350 X

Antimony (Sb) µg/l 1,2 113 3)

X

Arsenic (As) µg/l 13 4,3 3)

X

Barium (Ba) µg/l 240 9,3 3)4)

X

Calcium (Ca) mg/l 300 X

Cobalt (Co) µg/l 6,4 0,28 3)4)

X

Iron (Fe) mg/l 11 X

Magnesium (Mg) mg/l 79 X

Manganese (Mn) mg/l 1,4 0,15 3)4)

X

Molybdenum (Mo) µg/l 3,7 67 3)

X

Sodium (Na) mg/l 660 X

Selenium (Se) µg/l < 1 X

Silicon (Si) mg/l 15 X

Titan (Ti) µg/l 28 X

Vanadium (V) µg/l 8,3 4,1 3)4)

X

Lead (Pb) µg/l 3,4 0,34 3)

X

Cadmium (Cd) µg/l 0,11 ≤0,08-0,25 3)4)5)

X

Chromium (Cr) µg/l 11 CrVI 3,4

3)

CrIII 4,9 3)

X

Potassium (K) mg/l 460 X

Copper (Cu) µg/l 8,4 1 (12) 3)4)

X

Mercury (Hg) µg/l <0,05 0,05 3)4)

Nickel (Ni) µg/l 21 2,3 (3) 3)4)

X

Zinc (Zn) µg/l 68 7,8 3)4)

X

PCB compounds

PCB 28 µg/l < 0,01

PCB 31 µg/l < 0,01

PCB 52 µg/l < 0,01

PCB 101 µg/l < 0,01

PCB 105 µg/l < 0,01

PCB 118 µg/l < 0,01

PCB 138 µg/l < 0,01

PCB 153 µg/l < 0,01

PCB 156 µg/l < 0,01

PCB 180 µg/l < 0,01

PCB sum µg/l #

Phthalates

Di-n-butylphthalate (DBP) µg/l < 0,5 2,3

Benzylbutylphthalate (BBP) µg/l < 0,1 7,5

Diethylhexylphthalate (DEHP) µg/l 5,1 1,3

Diethylhexylphthalat (DEHP) µg/l 3,3 1,3

Di-(2-ethylhexyl)adipate (DEHA) µg/l < 0,1 0,7

Di-n-octylphthalate (DNOP) µg/l < 0,1

Diethylphthalate (DEP) µg/l 3,6

Diisononylphthalate (DiNP) µg/l < 0,3

Alkylphenoles and -ethoxylates

4-n-octylphenol µg/l < 0,1

4-t-octylphenol µg/l 0,2 0,1

4-tert-octylphenol monoethoxylate µg/l < 0,1

4-tert-octylphenol diethoxylate µg/l < 0,1

4-n-nonylphenol µg/l < 0,01 0,3

Nonylphenoles µg/l 0,8

Nonylphenolmonoethoxylates µg/l < 0,05

Nonylphenoldiethoxylates µg/l < 0,1

Sum of Nonylphenol+ethoxylates µg/l 0,8

PFAS

Perfluorobutanesulfonic acid (PFBS) µg/l < 0,01

Perfluordecanesulfonic acid (PFDS) µg/l < 0,005

Perfluoroheptanoic acid (PFHpA) µg/l < 0,025

9

Perfluorohexanesulfonic acid (PFHxS) µg/l < 0,005

Perfluorohexanoic acid (PFHxA) µg/l <5

Perfluorononanoic acid (PFNA) µg/l 0,082

Perfluorodecanoic acid (PFDA) µg/l 0,06

Perfluorooctanesulfonamide (PFOSA) µg/l 0,056

Perfluorooctane sulfonate (PFOS) µg/l 6,0 0,00065 6)

X

Perfluorooctanoic acid (PFOA) µg/l 4,0 X

Perfluoroundecanoic acid (PFUnA) µg/l < 0,005

Phenols

Phenol µg/l < 0,1 7,7

2-methylphenol µg/l 0,12

3-methylphenol µg/l < 0,05

4-methylphenol µg/l < 0,05

2,3-dimethylphenol µg/l 0,07






Sum dimethylphenols (6 congener) µg/l 0,63 13,1

Bisphenol A µg/l 8,8 0,1 X

Brominated flame retardants

BDE-28 µg/l < 0,005

0,0005

BDE-47 µg/l < 0,005

BDE-99 µg/l < 0,005

BDE-100 µg/l < 0,005

BDE-153 µg/l < 0,005

BDE-154 µg/l < 0,005

BDE-85 µg/l < 0,005

BDE-183 µg/l < 0,005

BDE-209 µg/l < 0,01

Aromatic hydrocarbons

Benzene µg/l 0,077 10

Toluene µg/l <0,02

Ethylbenzene µg/l <0,02 20

o-Xylene µg/l 0,041

m+p-Xylene µg/l 0,095

Sum af xylenes µg/l 0,14 10

BTEX (sum) µg/l 0,21

Naphthalene µg/l 0,032 2,4

Hydrocarbons

C6H6-C10 µg/l 8,2

C10-C25 µg/l 93

C25-C35 µg/l <9

Sum (C6H6-C35) µg/l 100

PAH compounds

Acenaphtene µg/l 0,046 3,8

Fluorene µg/l 0,048 2,3

Phenanthrene µg/l 0,016 1,3

Fluoranthene µg/l 0,035 0,1

Pyrene µg/l 0,036 0,0046

Benzo(b+j+k)fluoranthene µg/l <0,01 0,03

Benzo(a)pyrene µg/l <0,01 0,05

Indeno(1,2,3-cd)pyrene µg/l <0,01

0,002

Benzo(g,h,i)perylene µg/l <0,01

Sum of PAH µg/l 0,18

Dioxines and furanes

2,3,7,8-TetraCDD pg/l < 0,72

1,2,3,7,8-PentaCDD pg/l < 0,96

10

1,2,3,4,7,8-HexaCDD pg/l < 1,92

1,2,3,6,7,8-HexaCDD pg/l < 1,92

1,2,3,7,8,9-HexaCDD pg/l < 1,92

1,2,3,4,6,7,8-HeptaCDD pg/l 21,9

OctaCDD pg/l 219

2,3,7,8-TetraCDF pg/l < 3,00

1,2,3,7,8-PentaCDF pg/l < 1,72

2,3,4,7,8-PentaCDF pg/l < 1,72

1,2,3,4,7,8-HexaCDF pg/l < 1,60

1,2,3,6,7,8-HexaCDF pg/l < 1,60

1,2,3,7,8,9-HexaCDF pg/l < 1,60

2,3,4,6,7,8-HexaCDF pg/l < 1,60

1,2,3,4,6,7,8-HeptaCDF pg/l 6,38

1,2,3,4,7,8,9-HeptaCDF pg/l < 1,52

OctaCDF pg/l 10,8

Sum pg/l 258

WHO(1998)-PCDD/F TEQ (lower-bound) pg/l 0,306

WHO(1998)-PCDD/F TEQ (upper-bound) pg/l 4,46

WHO(2005)-PCDD/F TEQ (lower-bound) pg/l 0,352

WHO(2005)-PCDD/F TEQ (upper-bound) pg/l 4,13

I-TEQ (NATO/CCMS) (lower-bound) pg/l 0,513

I-TEQ (NATO/CCMS) (upper-bound) pg/l 4,19

1) The EQS expressed as an annual average value (AA-EQS). Unless otherwise specified, it applies to the total concentration of all isomers. Inland surface waters encompass rivers and lakes and related artificial or heavily modified water bodies. Unless otherwise specified, the EQS refers to Danish or European EQS set down in Statutory Order No. 1022 of 25/08/2010 /1/.

2) Direct limit values set down by local authorities – the values may differ from water body to water body. Based on DHI experience from discharge permits to inland surface waters.

3) In the case of metals the EQS refers to the dissolved concentration, i.e. the dissolved phase of a water sample obtained by filtration through a 0,45 μm filter or any equivalent pre-treatment.

4) In assessing the monitoring results or calculated concentrations in a water body the natural background concentration shall be taking into account, if it makes it impossible to comply with the EQS. A maximum value is indicated in parentheses if available.

5) The EQS is depending on the water hardness. 6) A European EQS on 0,00065 µg/l for Perfluorooctane sulfonic acid and its derivatives (PFOS) for inland surface

waters will apply from December 2015 /2/.

A tank truck of raw leachate from B16.9 at Waste Centre Skårup was subsequent delivered to

Grundfos BioBooster with the aim of testing the removal of pollutants from the leachate with

MBR technology.

A grab sample from the outlet of the BioBooster was send to DHI Århus for further testing with

Activated Carbon and ozone.

3.2 Results

The results of the analysis of the raw leachate from Waste Centre Skårup and the treated

leachate are shown in Table 3-4 together with the Environmental Quality Standards for inland

surface waters.

In all cases where leachate enters a water body, the discharge is subject to regulation in terms

of direct limit values on the concentration of certain substances in the leachate (i.e. for Total-P,

Total-N, SS, COD, chloride) depending on the local water body or in terms of resulting water

quality standards (EQS) of the water body into which the leachate is discharged (for metals and

organic pollutants).

11

The direct limit values are set down by the local environmental authorities depending on the

condition and objectives of the local water body. In Table 3-4 examples of direct limit values are

given based on DHI experience from discharge permits to inland surface waters.

The Environmental Quality Standard (EQS) for inland surface waters for the specific metals and

organic pollutants is either a national (DK) or European (EU) EQS specified in Statutory Order

No. 1022 of 25/08/2012 /1/, see Table 3-4.

In Table 3-4 all concentrations in the samples from raw and treated leachate are marked with

red color, if the concentrations are above the limit values or EQS. If the concentrations are more

than 10 times above the limit values or EQS the concentrations are marked with dark red.

It is important to be aware that in the case of metals the EQS refers to the dissolved

concentration (i.e. the dissolved phase of a water sample obtained by filtration through a 0.45

μm filter). The analyzed concentration of the metals in the seven samples of untreated and

treated leachate is the total concentration of metals.

An earlier study of leachate from the Waste deposit AV Miljø in 2008-2009 investigated the

effect of the concentration of metals in raw leachate after filtration through a 0.45 µm filter /4/,

see Table 3-3.

Table 3-3 Evaluation of the effect of filtration of leachate samples prior to chemical analysis /4/.

Evaluation Parameters Factor between pairs where both are above the detection limit

Decrease in result due to filtration Iron (Fe) Lead (Pb) Cadmium (Cd) Copper (Cu) Zinc (Zn) Aluminium (Al)

2-24 4-15 1-25 1-7 3-7 24-85

Possible/minor decrease in result due to filtration

Chromium (Cr) Arsenic (As) Barium (Ba) Molybdenum (Mo) Antimony (Sb)

1.0-1.6 1.0-3.5 1.1-2.0 1.0-2.1 1.3-2.1

Filtration causes no effect Manganese (Mn) Nickel (Ni) Silicon (Si) Calcium (Ca) Sodium (Na) Potassium (K) Cobalt (Co)

1.0-1.1 1.0-1.5 1.0-1.1 1.0 1.0 1.0 1.0

12

Table 3-4 Results from the analysis of landfill leachate from Waste Centre Skårup (sample 1-3), of MBR treated landfill leachate (sample 4-5), of MBR and Activated Carbon (AC) treated landfill leachate (sample 6) and of MBR and Ozone treated landfill leachate (sample 7). Local limit Values (L), National (DK) or European (EU) Environmental Quality Standards for inland surface waters are shown.

Component Unit Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 EQS1)

Raw landfill

leachate Raw landfill

leachate Raw landfill

leachate MBR treated

leachate MBR treated

leachate MBR and AC

treated leachate MBR and Ozone treated leachate

Inland surface waters2) L/DK/

EU3)

pH pH 7,5 8 8,1 8 8,1 9 8,4 6,5-9,0 L

Suspended Solids mg/l 62 100 46 0,8 0,7 0,9 2,3 25 L

Conductivity mS/m 640 450 470 460 450 360 440 - L

Ammonia+ammonium-N mg/l 140 87 96 0,032 0,02 0,027 0,15 1 L

Total-N mg/l 140 110 110 130 110 60 110 1 L

Total-P mg/l 1,3 1,5 0,65 5,7 5,2 1 4,8 0,1-0,15 L

Chloride mg/l 820 590 630 660 640 530 620 0,5-40 L

Sulfate mg/l 580 440 440 460 460 380 440 40 L

Hydrogen carbonate mg/l 2.100 1.300 1.400 630 620 580 600 - COD mg/l 310 240 230 180 170 20 160 30 L

NVOC mg/l 95 72 67 56 55 5,3 65 - Aluminium (Al) µg/l 350 330 54 < 30 < 30 140 < 30 - Antimony (Sb) µg/l 1,2 1,3 1,1 1,1 1 9,4 1,2 113

4) DK

Arsenic (As) µg/l 13 10 11 6,9 7 89 6,7 4,3 4)

DK

Barium (Ba) µg/l 240 190 150 43 43 91 43 9,3 4)5)

DK

Lead (Pb) µg/l 3,4 2,4 0,5 < 0,5 < 0,5 1,9 < 0,5 0,34 4)

DK 7)

Cadmium (Cd) µg/l 0,11 0,078 < 0,05 0,064 0,06 0,059 0,069 ≤0,08-0,25 4) 5) 6)

EU

Calcium (Ca) mg/l 300 210 190 240 230 130 230 - Chromium (Cr) µg/l 11 9,9 4,8 3,6 3,2 0,8 3,1 CrVI 3,4

4) / CrIII 4,9

4) DK

Cobalt (Co) µg/l 6,4 5,5 5,4 4,9 4,9 1,4 3,9 0,28 4) 5)

DK

Iron (Fe) mg/l 11 7,5 6,1 0,057 < 0,05 < 0,05 < 0,05 - Potassium (K) mg/l 460 330 340 370 360 310 340 - Copper (Cu) µg/l 8,4 17 4 21 18 6,5 18 1 (12)

4) 5) DK

Magnesium (Mg) mg/l 79 54 56 62 60 48 56 - Manganese (Mn) mg/l 1,4 0,67 0,51 0,27 0,24 0,028 0,19 0,15

4) 5) DK

Molybdenum (Mo) µg/l 3,7 6,8 5,9 6,3 6,3 88 4,9 67 4)

DK

Sodium (Na) mg/l 660 490 510 530 520 450 500 - Nickel (Ni) µg/l 21 33 17 34 32 8,8 29 2,3 (3)

4) 5) DK

8)

Selenium (Se) µg/l < 1 < 1 < 1 < 1 < 1 1,8 < 1 - Silicon (Si) mg/l 15 14 18 14 15 11 14 - Titan (Ti) µg/l 28 17 < 5 < 5 < 5 < 5 < 5 - Vanadium (V) µg/l 8,3 6,5 5,9 5,8 4,5 69 4,2 4,1

4) 5) DK

Zinc (Zn) µg/l 68 73 32 41 30 8,5 23 7,8 4) 5)

DK

PFOS µg/l 6,0 0,75 0,78 0,58 0,5 0,016 0,19 0,00065 EU 9)

PFOA µg/l 4,0 0,47 0,51 0,5 0,51 0,056 0,15 - Bisphenol A µg/l 8,8 0,01 0,03 0,05 0,05 0,14 0,02 0,1 DK

13

1) The EQS expressed as an annual average value (AA-EQS). Unless otherwise specified, it applies to the total concentration of all isomers. 2) Inland surface waters encompass rivers and lakes and related artificial or heavily modified water bodies. 3) [L] refers to typically direct limit values set down by local authorities – the values may differ from water body to water body. Based on DHI experience from discharge permits to

inland surface waters. [DK] refers to Danish national Environmental Quality Standards and [EU] refers to European Environmental Quality Standards both set down in Statutory Order No. 1022 of 25/08/2010 /1/.

4) In the case of metals the EQS refers to the dissolved concentration, i.e. the dissolved phase of a water sample obtained by filtration through a 0,45 μm filter or any equivalent pre-treatment.

5) In assessing the monitoring results or calculated concentrations in a water body the natural background concentration shall be taking into account, if it makes it impossible to comply with the EQS. A maximum value is indicated in parentheses if available.

6) The EQS is depending on the water hardness. 7) A European EQS on 1.2 µg/l (bioavailable concentration) for inland surface waters will apply from December 2015 /2/, but the Danish EQS on 0.34 µg/l is expected to remain in

force. 8) A European EQS on 4.0 µg/l (bioavailable concentration) for inland surface waters will apply from December 2015 /2/, but the Danish EQS on 2.3 µg/l is expected to remain in

force. 9) A European EQS on 0.00065 µg/l for Perfluorooctane sulfonic acid and its derivatives (PFOS) for inland surface waters will apply from December 2015 /2/.

14

3.3 Discussion

3.3.1 Screening of raw leachate for metals and organic micro pollutants

The first sample of raw leachate from Waste Centre Skårup (sample 1) was analyzed for a large

number of metals and organic micro pollutants, see Table 3-2. The results show that with

regards to discharging the untreated leachate to inland surface water the concentrations of

COD, ammonia-ammonium-N, total phosphorous, total nitrogen, chloride, sulfate, barium,

cobalt, copper, nickel, zinc, PFOS and bisphenol A will exceed the discharge limit values or the

Environmental Quality Standards at least ten times.

The concentrations of suspended solids, arsenic, lead, cadmium, chromium, manganese,

vanadium and the organic micro pollutants DEHP, pyrene, octyl- and nonylphenols in the raw

leachate were also measured in concentrations above the discharge limit values or the

Environmental Quality Standards.

For the metals copper, zinc, lead and cadmium the dissolved concentrations in the raw leachate

can be expected to be up to a factor 3-25 lesser than the measured total concentration

depending on the specific metal, see Table 3-3. This means that the dissolved concentration of

cadmium and lead in the raw leachate probably will not exceed the EQS. For the rest of the

metals the filtration will have lesser or no effect on the concentration and the dissolved

concentrations therefore are still expected to exceed the EQS.

There exists no Environmental Quality Standard for inland surface waters for dioxins and furans.

The measured concentrations of dioxins and furans in the raw leachate (0,352 pg/l) was on the

same level as concentrations measured in the outlet from two large municipal WWTP’s in

Copenhagen (0,097-1,51 pg/l) and concentrations measured in The Sound (0,055-0,377 pg/l) in

2009-2010 expressed as toxic equivalents (WHO(2005)-PCDD/F TEQ) /3/.

The screening of the first sample of the raw leachate for metals and organic micro pollutants

indicated, that concentrations of phenols, hydrocarbons, aromatic hydrocarbons, polyaromatic

hydrocarbons (except pyrene), phthalates (except DEHP), brominated flame retardants and

PCB where generally low and did not exceed the EQS (if it exist).

The concentration of the analyzed components showed generally the same level in all three

samples of raw leachate, except for PFOS/PFOA and bisphenol A, where the concentrations of

PFOS and PFOA where approximately 8 times higher in sample 1 compared to sample 2 and 3.

The concentration of bisphenol A where approximately 300 times higher in sample 1 compared

to sample 2 and 3.

3.3.2 The effect of MBR, Active Carbon and Ozone on concentrations of metals and organic micro pollutants

Table 3-5 illustrates the compliance between the measured concentrations in raw and treated

leachate and the discharge limit values/EQS.

15

Table 3-5 Compliance between the concentrations in the raw/treated leachate and the discharge limit values/EQS. A minus indicates that the concentrations do not comply with the discharge limit values/EQS, while a plus indicates that the concentrations do comply. A dark red color indicates, that the concentration is more than ten times the discharge limit value/EQS.

Parameters Raw leachate MBR treated leachate

MBR and AC treated leachate

MBR and ozone treated leachate

Suspended solids - + + +

COD - - + -

Ammonia-ammonium-N - + + +

Total phosphorous - - (increased)* - (but reduced)** -

Total nitrogen - - - (but reduced)** -

Chloride - - - -

Sulfate - - - -

Barium (Ba) - - (but reduced)* - (increased)** -

Cobalt (Co) - - - (but reduced)** -

Copper (Cu) - - - (but reduced)** -

Nickel (Ni) - - - (but reduced)** -

Zinc (Zn) - - - (but reduced)** -

Arsenic (As) - - (but reduced)* - (increased)** -

Lead (Pb) (-) + - (increased)** +

Cadmium (Cd) (-) + + +

Chromium (Cr) - + + +

Manganese (Mn) - - (but reduced)* + -

Vanadium (V) - - - (increased)** -

PFOS - - - (but reduced)** - (but reduced)**

Bisphenol A + + - (increased)** +

* Compared to the concentrations in raw leachate ** Compared to the concentrations in MBR treated leachate

The four samples from the inlet (sample 2 and 3) and outlet (sample 4 and 5) of the MBR

treatment (Grundfos BioBooster) indicates a reduction of the concentrations of suspended

solids, ammonia-ammonium-N, lead, cadmium and chromium to below the discharge limit

values/EQS for inland surface waters. The concentrations of barium, arsenic and manganese

were also reduced, but the measured concentrations in the outlet from the MBR treatment were

still above the EQS.

The concentrations of the organic micro pollutants PFOS and PFOA were not significantly

reduced with the MBR treatment and would still pose a problem with discharge of MBR treated

leachate to inland surface waters.

The sample of the Activated Carbon filtrated leachate (sample 6) indicates a further reduction of

the concentrations of COD and manganese to below the discharge limit values/EQS as a result

of the Active Carbon filtration. The concentrations of total phosphorous, total nitrogen, cobalt,

copper, nickel, zinc and PFOS were also reduced, but the concentrations were still above the

discharge limit values/EQS.

The sample of Activated Carbon treated leachate (sample 6) shows significantly higher

concentrations of a number of metals compared to the concentrations in the two samples from

the outlet of the Grundfos BioBooster. It concerns aluminium, antimony, arsenic, barium, lead,

molybdenum and vanadium, see Table 3-4. The said samples were reanalyzed for the metals of

concern, but the results remained the same. No explanation as to the increased concentrations

of metals has been found.

As expected the sample of MBR and Ozone treated leachate (sample 7) shows no difference in

concentrations for any of the analyzed components compared to the MBR treated leachate

16

(sample 5) except for PFOS and PFOA (and to some extend bisphenol A). The concentration of

PFOS and PFOA were reduced with a factor 2.6 and 3.4 respectively compared to the MBR

treated leachate. However the Activated Carbon appears to result in a more efficient removal of

PFOS and PFOA with a reduction in the concentration of a factor 31 and 9 respectively.

None of the three conducted tests of treatment technologies resulted in a removal of PFOS

below the EQS of 0.00065 µg/l.

The degree of removal for the various parameters by MBR-treatment, activated carbon

treatment and ozonation is illustrated in figure 3-2.

Figure 3-2 Degree of removal by MBR-treatment, activated carbon-treatment and ozonation.

For MBR-treatment the degree of removal is based on the average of the two inlet samples and

the two outlet samples. It should be noted that for a number of combinations of parameters and

treatment process, the degree of removal was negative (i.e. lower concentrations in the inlet as

compared to the outlet). The negative columns for these cases are omitted in figure 3-2, as it is

assumed that the negative values in most cases are caused by analysis errors or analysis

uncertainty.

0

10

20

30

40

50

60

70

80

90

100

Rem

ova

l (%

)

MBR

AC

O3

0

10

20

30

40

50

60

70

80

90

100

Rem

ova

l (%

)

MBR

AC

O3

17

18

4 COD-fractionation and inhibition of nitrification – tests in laboratory scale

At the DHI laboratory in Hørsholm, various tests were done with the aim of characterizing the

leachate in terms of its treatability in a biological process. In addition to basic chemical analysis

of the leachate, batch tests were conducted to measure COD-fractions (short and long term

degradability) as well as the degree of inhibition of the nitrification process. Sections 4.1-4.3

below, contains a brief description of the test setup and the obtained results.

4.1 Chemical analysis of raw leachate

Tests were done one two different samples of leachate from Skårup landfill. Sample 1 was

collected as a grab sample on June 27th 2014. The sample contained considerable quantities of

dark suspended settable solids. These solids may be a result of on-going chemical precipitation

of sulphide at the time of sampling. The supernatant was somewhat unclear and yellowish.

Sample 2 was taken from the last truckload of leachate delivered to Grundfos. This sample

contained less suspended solids and was clear yellow. In table 4-1 is shown the results of basic

chemical analysis of the two samples.

Parameter Sample 1 Sample 2 Unit pH 7.1 7.9

Conductivity 9.9 4.8 mS/cm Suspended solids 560 - mg/l Volatile suspended solids 140 - mg/l Ammonium nitrogen 129 98 mg/l Total nitrogen 166 - mg/l COD 437 210 mg/l COD filtered 415 - mg/l Chloride 2,140 - mg/l Sulphide 3.9 < 0.1 mg/l

Table 4-1 Chemical analysis of leachate samples

As it appears from table 4-1 sample 1 is more concentrated than sample 2. It should also be

noted that sample 1 contains sulphide contrary to sample 2.

4.2 COD-fractionation

The COD-content of a waste water sample can be characterized in terms of its degradability in a

biological treatment system, by contacting the waste water sample to activated sludge and

measuring the resulting oxygen uptake rate (OUR) in batch tests. A high OUR in a batch mixture

containing the waste water sample in question, as compared to a reference containing only

activated sludge and tapwater, indicates the presence of easily degradable COD in the waste

water. The quantity of consumed oxygen during the batch test is proportional to the content of

COD degraded and by comparing this quantity to the total content of COD, the fraction of

degradable COD can be calculated as a percentage of the total COD content.

OUR-tests with the aim of COD-fractionation were conducted by the use of the laboratory setup

shown in figure 4-1. The setup consists of four batch reactor equipped with DO- and

temperature sensors. The reactors are automatically aerated between two DO-setpoints, and

DO-data is collected by a PC and transformed to OUR-rates.

19

Figure 4-1 Laboratory set up for OUR tests

Test were conducted according to table 4-2 below.

Table 4-2 Reactor set up for the conducted fractionation test.

In all cases, activated sludge from Mølleåværket in Lundtofte was added to the medium to reach

a resulting MLSS-concentration of approximately 2 g SS/l. Alylthiourea (ATU) was added in all

cases to inhibit nitrification, so that oxygen consumption is only caused by degradation of COD.

Key results from the tests are shown in table 4-3 below.

Test Date

Sample Dilution factor

Leachate COD

in mixture (mg/l)

Oxygen consumption from leachate

(mg O2/l)

Quantity of degraded COD

(mg/l)*

Degradable COD in

relation to total COD (%)

1/7-14 1 1.5 291 3.3 13 4.5

3/7-14 1 1.5 291 3.5 14 4.8 5.2 84 1.5 6 7.1

3/9-14

2 1.5 140 1.0 4.0 2.9 2.5 84 0.5 2.0 2.4 5.0 42 0.3 1.2 2.9

Table 4-3 Results from COD-fractionation tests.

From table 4-3 it can be seen that in general, it is only a small fraction (3-7%), of the COD-

content in the leachate that is degradable under the prevailing conditions. It also appears from

Date Reactor nr. Medium

1/7-14 1 Tap water + ATU 2 1.5 x diluted leachate (sample 1) + ATU

3/7-14 1 Tap water + ATU 2 1.5 x diluted leachate (sample 1) + ATU 3 5.2 x diluted leachate (sample 1) + ATU

3/9-14

1 Tap water + ATU 2 1.5 x diluted leachate (sample 2) + ATU 3 2.5 x diluted leachate (sample 2) + ATU 4 5.0 x diluted leachate (sample 2) + ATU

20

the table, that the content of degradable COD seems to be higher for sample 1 than for sample

2. Finally it can be seen that for sample 1 a high dilution results in a higher measured content of

degradable COD, indicating a possible inhibition effect at low dilution. This is not the case for

sample 2, and this is consistent with the fact that sample 2 originally was less concentrated than

sample 1.

4.3 Long term COD degradation

As it appears from the short term COD-fractionation tests reported in section 2.2, the content of

degradable COD is very low. In order to see if longer contact between the activated sludge

bacteria and the leachate could accomplish further degradation, long term tests were conducted

by continuously running the batch reactors started on 3/7 (sample 1) and 3/9 (sample 2) for a

total of 5 days.

After the small initial increase in OUR seen in the short term tests, the OUR in all cases rapidly

decreased to an endogenous level, that corresponded to the level of the reference without

leachate. During the following 5 days the OUR for all reactors with leachate, slowly decreased

further in accordance with the reference. Hence, there was no sign that long term contact could

induce further COD degradation.

4.4 Inhibition of nitrification

A number of nitrification inhibition tests were conducted on the two samples, to see if the

leachate contains compounds with an inhibiting effect on the nitrification process. The

nitrification tests were based on OUR measurements using the setup shown in figure 4-1. To

measure the nitrification rate two identical tests are conducted, the only difference being that

ATU is added to one of the batches. By subtracting the resulting two OUR curves oxygen uptake

caused by nitrification alone can be obtained. Inhibition of nitrification from the leachate is

measured by comparing a set of test containing leachate with a reference containing tap water

instead of leachate.

Batch reactor mixtures were setup according to table 4-4. In all cases, activated sludge from

Mølleåværket in Lundtofte was added to the medium to reach a resulting MLSS-concentration of

approximately 2 g SS/l.

Table 4-4 Reactor set up for the conducted nitrification inhibition test

Key results from the tests are shown in table 4-5 (sample 1) and 4-6 (sample 2) below.

Date Reactor nr. Medium

3/7-14

1 Tap water + ammonium (reference) 2 Tap water + ammonium + ATU (reference) 3 1.5 x diluted leachate (sample 1) 4 1.5 x diluted leachate (sample 1) + ATU 5 5.2 x diluted leachate (sample 1) 6 5.2 x diluted leachate (sample 1) + ATU

2/9-14

1 Tap water + ammonium (reference) 2 Tap water + ammonium + ATU (reference) 3 1.5 x diluted leachate (sample 2) 4 1.5 x diluted leachate (sample 2) + ATU

3/9-14

1 Tap water + ammonium (reference) 2 Tap water + ammonium + ATU (reference) 3 5.2 x diluted leachate (sample 2) 4 5.2 x diluted leachate (sample 2) + ATU

21

Reactor nr Observed OUR

mg O2/(l*h)

Δ OUR mg O2/

(l*h)

N-rate* mg NH4-N/

(l*h)

N-rate** mg NH4-N/

(g SS*h)

Inhibition %

1 (Reference) 37 31 6.8 3.4 - 2 (Reference + ATU) 6 3 (1.5 x diluted sample 1) 13 8 1.8 0.9 74 4 (1.5 x diluted sample 1 + ATU) 5 5 (5.2 x diluted sample 1) 25 20 4.4 2.2 35

6 (5.2 x diluted sample 1 + ATU) 5

* 4.56 mg O2/mg NH4-N nitrified. **6 g SS/l

Table 4-5 Results from nitrification inhibition test conducted 3/7-14

As it appears from table, 4-5, sample 1 leachate diluted only 1.5 times, shows a high degree of

inhibition (74%). When diluted 5.2 times, inhibition is reduced by a factor of two, but inhibition is

still considerable.

The same tests conducted on sample 2 (table 4-6), showed a much lower degree of inhibition

than those conducted at sample 1. Hence with the low dilution factor of 1.5, inhibition was

measured at 19%, and no inhibition was seen at a dilution factor of 5.2.

Reactor mixture Observed OUR

mg O2/(l*h)

Δ OUR mg

O2/(l*h)

N-rate* mg NH4-N/

(l*h)

N-rate mg NH4-N/

(g SS*h)

Inhibition %

1 (Reference) 28 24 5.3 3.1 - 2 (Reference + ATU) 4 3 (1.5 x diluted sample 2) 23 19 4.2 2.5 19 4 (1.5 x diluted sample 2 + ATU 4

1 (Reference) 26 23 5.0 3.0

- 2 (Reference + ATU) 3 3 (5.2 x diluted sample 2) 26 23 5.0 3.0 0

4 (5.2 x diluted sample 2 + ATU 3

* 4.56 mg O2/mg NH4-N nitrified. **5.2 g SS/l

Table 4-6 Results from nitrification inhibition test conducted 2-3/9 2014

22

5 Aeration and pH-adjustment – test in laboratory scale

When treating leachate in an MBR system, a pre-treatment stage might be desirable, for

instance to remove iron that might cause scaling on the membranes, or to remove heavy metals

or other pollutants that may not be removed to a sufficient degree in the MBR system alone, or

may have a negative effect on the biology of the MBR-system.

On this background, two pre-treatment methods, aeration and pH-adjustment, were tested in

laboratory scale at the Grundfos laboratory in Langå. Aeration was mainly done with a focus on

iron precipitation, whereas pH adjustment was done with a broader focus on precipitation in

general. A brief description of the tests is given in section 3.1 and 3.2 below. For a more

detailed description please refer to Appendix A.

5.1 Aeration

Tests were done on two samples. Sample nr. 1 (sampled July 2nd

) differed from sample nr. 2

(sampled 11th July) by being more concentrated and having a content of sulphide. Sample 1 and

2 is also referred to as “contaminated” and “non-contaminated” respectively. The test setup is

shown in figure 5-1 below.

Figure 5-1 Setup for aeration test in laboratory scale

5 l of each of the two samples was aerated (fine bubble) for 6 hours. During the test period pH,

DO, temperature and conductivity was measured approximately every hour. In addition to this,

samples were taken from the aeration reactors for later analysis for iron at the Grundfos

laboratory. These samples were taken approximately once pr. hour and the samples were

filtered immediately through 0.45 µm filters and preserved with acid.

The results of the test are shown in figure 5-1 below.

23

Figure 5-2 Results from aeration tests. Top: Sample 1. Bottom: Sample 2.

As it appears from figure 5-1, it was difficult to increase DO in sample 1. This is in agreement

with sample 1 being more concentrated and thus having a higher chemical (and biological ?)

oxygen consumption than sample 2.

Looking at the concentration of iron, it can be seen that the concentration actually increases in

sample 1. This is contrary to expectations and no obvious explanation can be offered. In sample

2 the concentration of dissolved iron decreases as expected. The reduction observed is a little

less than 50%

5.2 pH-adjustment

Tests were done on the same two samples as used for the aeration test (see section 5.1).

30 % sodium hydroxide (NaOH) was used for pH-adjustment. The chemical was added in

different quantities to different batches of leachate. Samples were mixed for 30 minutes, and

visual inspection as well settling of precipitate, were observed. pH, conductivity and temperature

of the samples were also measured every 10 minutes.The setup for is shown in figure 5-3

below.

24

Figure 5-3 Setup for pH adjustment test in laboratory scale

Three batch tests were done on each of the two samples of leachate. The three batch test

differed only in the amount of NaOH added. The quantity of added NaOH in the different tests is

shown in table 5-1. Approximately 10 minutes after addition of NaOH, the measured test

parameters of pH, conductivity and temperature reach a stable level that was maintained

throughout the remaining test period. The levels after stabilization is shown in table 5-1.

Sample NaOH addition (mg 30%

NaOH pr. L of leachate) pH

Conductivity

(mS/cm)

Temperature

(°C)

1 (contaminated)

0 7.5 22 17-21

5 9.5 23 22

10 11.2 11.8 25

20 12.5 27 22

2 (non-contaminated)

0 7.5 7.4 20-25

5 9.9 8.0 22

10 11.2 11.8 25

20 12.5 27 22

Table 5-1 pH, conductivity and temperature in raw leachate and after addition of 5, 10 and 20 mg 30% NaOH pr. l of leachate.

The effect of pH adjustment was evaluated through visual inspection of sedimentation in conical

glasses. The photo to the left in 5-4 shows conical glasses with leachate where the left most

glass has received 20 mg 30% NaOH pr. l of leachate, whereas the right most is a reference

without addition of NaOH. The photo to the right shows the same as the photo to the right, only

with leachate from sample 2. As it appears from figure 5-4, addition of NaOH causes the

formation of settling flocs in both samples of leachate. It was noted that in general the size of the

formed flocs increased with the quantity of NaOH added, and further to this that the flocs were

bigger for tests with sample 1 than for tests with sample 2. As can clearly be seen from figure 5-

4, the supernatant was darker and more unclear for test with sample 1, than for test with sample

2.

25

Figure 5-4 Effect of pH-adjustment (20 mg 30% NaOH pr. l of leachate) on settling/precipitation of leachate sample 1 (Left) and leachate sample 2 (Right).

26

6 Biological treatment of leachate – test in pilot scale

6.1 Pilot plant setup

A main objective of the project was to evaluate the feasibility of biological treatment of the

leachate using MBR-technology. To do this a pilot scale test was conducted by Grundfos, using

leachate transported by truck from Skårup landfill, to feed a pilot scale MBR plant located at the

Grundfos test facility in Bjerringbro. A schematic flow diagram of the pilot plant is shown in figure

6-1.

Figure 6-1 Schematic diagram of the MBR-pilot scale system

Key operational parameters for the pilot plant are shown in table 6-1.

Parameter Value Unit

Number of test run days 21 Days

Hourly inlet flow 0,2 m3/hr

Hourly permeate flow* 0.5-0.8 m3/hr

Reactor tank size 10 m3

MLSS concentration 4-6 kg /m3

pH 7-8 pH

MLSS temperature 18-21 °C

Dissolved oxygen in tank 2-3 mg/Lit

*Permeate was recirculated over the membranes

Table 6-1 Key operational parameters for the pilot plant test.

6.2 Operation of the biological process

The pilot plant was started on freshly collected activated sludge from a nearby municipal

WWTP. No screening or any other treatment of the leachate was applied prior to feeding the

leachate to the biological reactor.

The concentration of MLSS in the biological reactor was approximately 6.5 g SS/l at start up. As

shown in figure 6-3, the MLSS-concentration decreased to a little less than 5 g SS/l during the

27

first couple of days, but was then constant or slightly increasing for the rest of the test period.

From figure 6-3 it also appears that contrary to the MLSS-concentration, the VSS/SS-ratio

decreased almost lineary through the whole test period. This indicates accumulation of inorganic

material while the content of organic material is decreasing, presumably also the biomass

necessary for the biological treatment.

Figure 6-2 Development in concentrations of MLSS and MLVSS during the test period.

The nitrification rate of the activated sludge of the pilot plant was measured once a week

through batch tests based on monitoring of nitrate generation rates.

Figure 6-3 Development in the nitrification rate of the activated sludge during the test period.

As it appears from figure 6-4 the sludge originally had a specific nitrification rate of

approximately 0.9 g NO3-N/(kg VSS * h). This is a typical rate for the municipal WWTP where

the sludge for the pilot plant was collected. It further appears from figure 6-4, that during the first

2 weeks the nitrification rate increased somewhat, whereas during the last week of operation it

decreased to below the originally rate of the sludge. The initial increase could be caused by an

increase in the load of ammonia as compared to the conditions at the municipal WWTP. The

decrease at the end of the test period may indicate an inhibitory effect by the leachate of last

batch transported to the pilot plant.

6.3 Operation of the membrane filters

As indicated in figure 6-1 and table 6-1, permeate was recirculated to the process tank so that

the permeate flow was 2.5 – 4 times higher than the inlet flow. This was done in order to

28

maintain a hydraulic load of the membranes comparable to typical membrane operation. Other

main operational parameters for the membrane filters are given in table 5-1.

Table 6-2 Key parameters for operation of the membrane filters

In figure 6-5 is shown the net flux during the test period. As it appears from figure 6-5, the net

flux at the start of the test period is a little less than 30 LMH and decreases to 20 LMH during

the first week of operation. Chemically enhanced back flush (CEB) is then applied for around

two days, which brings the flux up to 25 LMH, i.e. the recovery is over 80%. Some four days

later the flux has declined to a little less than 20 LMH, and a second CEB increases the flux to

over 25 LMH. The observed level of flux and recovery by CEB, seems acceptable.

Figure 6-4 Development in net flux during the test period.

6.4 Permeate quality

The performance of the biological treatment was monitored through measurement of traditional

parameters (COD, NH4 and TP), as well as of selected micro organic pollutants.

Traditional wastewater parameters

COD, NH4 and TP was measured both the inlet and the outlet of the pilot plant. Measurements

were done approximately every day except weekends. In figure 5-6 is shown the concentrations

of COD, NH4 and TP in the inlet and outlet of the pilot plant.


TMP 0,5 bar

Filtration time 600 sec

Backwash time (@ diff. 0,5 bar) 20 sec

Relaxation time 0 sec

Sludge pressure 1,3 bar

MFU RPM 130 RPM

29

Figure 6-5 COD (top), NH4 (middle) and TP (bottom) in and out of the pilot plant.

As it appears from the COD curves the COD-concentration in the inlet decreases during the test

period from around 350 mg/l to around 240 mg/l. Hence the different truckloads of leachate had

decreasing concentrations of COD. It further appears that during the first couple of days, the

difference between the concentration in the inlet and outlet is relatively big. This is however due

to dilution as the concentration of dissolved COD in the mixed liquor is probably at level of 30-50

mg/l. After the initial “wash out” of the reactor, it can be seen that difference between inlet and

outlet is rather small corresponding to a COD-removal efficiency in the interval of 10-30%.

30

From the curve in the middle of figure 6-5 it appears that in general there is full nitrification with a

level of ammonia in the outlet of less than 0.5 mg N/l. All nitrogen was converted to nitrate so

that the concentration of TN in the outlet was at the same level as in the outlet (not shown).

Measurement of influent TP turned out to be difficult, probably because of interfering

compounds in the raw leachate, and the results are therefore not included in figure 5-6. The

concentration of TP in the effluent of the pilot plant was typically in the interval of 5-10 mg/l. This

means that a phosphorous removal process, probably addition of precipitation chemicals, would

have to be included in order to comply with demands for discharge directly to the recipient.

Reduction of heavy metals and selected micro organic pollutants

Results from analysis of metals and microorganic pollutants are shown in table 3-4. Sample 3

and 4 represents the inlet to the MBR pilot plant and sample 5 and 6 represents the outlet

(permeate). Compliance with EQS-values is shown in table 3-5, and degree of removal is

illustrated in figure 2-3.

As indicated in table 3-5 the results shows a reduction of the concentrations of suspended

solids, ammonia-ammonium-N, lead, cadmium and chromium to below the discharge limit

values/EQS for inland surface waters. The concentrations of barium, arsenic and manganese

were also reduced, but the measured concentrations in the outlet from the MBR treatment were

still above the EQS.

The concentrations of the organic micro pollutants PFOS and PFOA were not significantly

reduced with the MBR treatment and would still pose a problem with discharge of MBR treated

leachate to inland surface waters.

31

7 Treatment with activated carbon and ozone – tests in laboratory scale

At the DHI laboratory in Århus, tests were done to evaluate activated carbon treatment and

ozonation, as a post treatment steps for treated leachate from biological treatment in the

Grundfos MBR-system. The tests were done with a special focus on micro organic pollutants.

A sample of permeate (biologically treated leachate) was obtained from the Grundfos MBR pilot

plant during the last week of the pilot test period. Part of the sample was used for the activated

carbon test, while another part was used for the ozonation test. The effect of the treatment

methods was evaluated through measurement of UV absorbance at 254 nm. UV absorbtion at

this wave length can be correlated almost directly with the content of COD. In addition to this a

sample of the untreated permeate as well as of the activated carbon treated permeate, and the

ozone treated permeate, was analysed for selected micro organic pollutants.

The test were done solely with the aim of evaluating the potential of the two treatment methods,

hence “full throttle” test conditions were applied in both cases.

7.1 Activated carbon treatment

The laboratory set up for activated carbon treatment is shown in figure 7-1.

Figure 7-1 Laboratory set up for treatment with activated carbon.

The activated carbon column is placed inside the blue filter housing in the background in figure

7-1.

As mentioned above, the test strategy was to solely look at the potential of activated carbon

treatment, i.e. the column was operated at a relatively long hydraulic retention time and

evaluation of the performance was done on an effluent sample taken after only 12 bed volumes.

The effect of the activated carbon treatment was evaluated based on absorbance at 254 nm, as

32

well as by chemical analysis of selected organic micro pollutants. Key parameters for the test

conditions of the activated carbon test are shown in table 7-1.


Design Flow 0,0024 m³/time

Design Flow 2,4 l/h

Filter velocity 0,9 m³/m²×time

Filter velocity 40 ml/min

EBCT 29,3 min

EB-Volume 0,0012 m³

EB-Volume 1,1726 liter/bedvol

Cross sectional area 0,003 m²

Bed volume pr. hour 2,05 BV/h

Bed height 0,5 m

FB 1 mm

Filtrasorb F400 particle size 0,1 cm

Table 7-1 Key operational parameters

In table 7-2 is shown the results of a basic characterization of the permeate before treatment.


pH 7,4 [-]

Conductivity 4,6 [mS/cm]

Salinity 2,4 [%]

Absorbance v. 254 nm 1,56 [cm-1

]

Transmission v. 254 nm 2,8 [%T]

Table 7-2 Characteristics of untreated permeate sample.

In table 7-3 is shown the absorbance at 254 nm before and after activated carbon treatment.


Absorbance v. 254 nm in raw leachate sample 1,56 [cm-1

] Absorbance v. 254 nm after 12 bed volumes 0,092 [cm

-1]

Change in absorbance compared to raw leachate sample 99 %

Table 7-3 Effect of activated carbon treatment based on absorbance at 254 nm.

As it appears from table 7-3, activated carbon treatment under the prevailing test conditions

almost completely removes absorbance, thereby indicating an extensive removal of COD.

Results from analysis of metals and microorganic pollutants are shown in table 3-4. Sample 5

represents the inlet to activated carbon treatment and sample 6 represents the outlet.

Compliance with EQS-values is shown in table 3-5, and degrees of removal is illustrated in

figure 3-2.

The results indicate a further reduction of the concentrations of COD and manganese to below

the discharge limit values/EQS as a result of the Active Carbon filtration. The concentrations of

33

total phosphorous, total nitrogen, cobalt, copper, nickel, zinc and PFOS were also reduced, but

the concentrations were still above the discharge limit values/EQS.

The sample of Activated Carbon treated leachate shows significantly higher concentrations of a

number of metals compared to the concentrations in the two samples from the outlet of the

Grundfos BioBooster. It concerns aluminium, antimony, arsenic, barium, lead, molybdenum and

vanadium, see Table 3-4. The said samples were reanalyzed for the metals of concern, but the

results remained the same. No explanation as to the increased concentrations of metals has

been found.

Activated carbon treatment resulted in considerable removal of PFOS with a reduction factor of

31, but the measured outlet concentration is still around 25 times higher than EQS-value of

0.00065 µg/l.

7.2 Ozone treatment

The laboratory set up is shown in figure 7-2.

Figure 7-2 Laboratory set up for ozone treatment

The test strategy was to solely look at the potential of ozone treatment, i.e. the reactor was

operated at a very high ozone dose. The effect of the ozone treatment was evaluated based on

absorbance at 254 nm, visual inspection of colour removal, and chemical analysis of selected

organic micro pollutants.

Key parameters for the test conditions of the ozonation test are shown in table 7-5.


Gas flow 2 l/min

Power settings 5,5 -

Measured absorbance 1,274

Gas ozone concentration 20,4 mgO3/l

Ozone load 2,4 g/h

34

Water volume in column 2 l

Measured equilibrium conc. mgO3/l

Table 7-4 Key operational parameters for ozone treatment

In table 7-6 is shown the measured absorbances at 254 nm and pH-values as a function of time

after start of ozonation, as well as the concentration of ozone transferred.

Time (min)

Ozone conc. transferred (mgO3/l)

UV 254 nm

pH

0 0 1,56 7,6

1 15 1,28 7,8

2 29 1,13 7,8

3 41 1,03 7,8

6 75 0,84 7,9

10 116 0,71 8

15 177 0,62 8,05

20 250 0,59 8,1

Table 7-5 Effect of transferred ozone dose on absorbance and pH

In figure 7-4 is plotted the measured absorbances against the concentration of ozone

transferred.

Figure 7-3 Absorbance as a function of transferred ozone dose

As it appears from figure 7-3 ozone treatment at the prevailing test conditions removes more

than 60% of the absorbance, indicating a similar degree of COD-removal.

From a visual inspection of the change in colour of the permeate during ozonation (figure 7-4), it

can be seen that ozone treatment can remove the yellowish colour of the permeate completely.

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

0 50 100 150 200 250 300

Ab

sorb

ance

v.

25

4 n

m [

cm-1

]

Ozone dose transferred to sample [mgO3/l]

35

Figure 7-4 Colour of leachate samples after various periods of ozone treatment. Numbers on bottles refers to minutes of treatment

In table 7-4 is shown the results of the analysis of selected micro organic pollutants.

Results from analysis of metals and micro-organic pollutants are shown in table 3-4. Sample 5

represents the inlet to the ozone treatment and sample 7 represents the outlet. Compliance with

EQS-values is shown in table 3-5, and degree of removal is illustrated in figure 3-2.

As it appears from table 3-4, the sample of MBR and Ozone treated leachate shows no

difference in concentrations for any of the analyzed components except for PFOS and PFOA

(and to some extend bisphenol A). The concentration of PFOS was reduced with a factor 2.6,

i.e. ozone was much less effective than activated carbon with a measured reduction factor of 31.

8 Treatment scenarios and further work

The experimental work carried out in this project aimed at a preliminary evaluation of a general

treatment train consisting of:

Based on the results of the experimental work, a pre-treatment process based on addition of

caustic seems interesting as considerable of quantities of sludge flocs was formed in the

laboratory experiments. However further work needs to be with this process especially to

evaluate the removal of specific compounds, and to optimize the caustic dose which was rather

high in the conducted tests, and therefore might result in unrealistic high opex.

The MBR pilot test showed that the membrane filters could be operated with a good flux and no

unusual or unacceptable fouling/scaling issues. Further to this it was shown that full nitrification

seems possible with complete removal of ammonia as a result. In addition to this a number of

metals were removed by adsorption to the activated sludge. The test also showed, as expected,

a complete removal of suspended solids. This is a very important feature of the MBR technology

as opens up for an efficient process for polishing of the permeate. COD removal and sludge

production was rather low, indicating that sustainable biological treatment might be problematic

because of a low degradability, and a low concentration in general, of the organic matter in the

leachate. A main focus in the further work, should therefore be to develop a concept for

Pre-treatment

Biological MBR-

treatmentPolishing

RawLeachate

Discharge to recipient

36

operation of the biological stage. One possibility could be to apply ozone treatment after pre-

treatment, in order to break down the organics to compounds that are more easily degradable in

the biological stage. Another solution could be to add external carbon to the biological stage.

This would be especially attractive if some waste product would be available e.g. from an

industrial source.

The two polishing processes tested were included with the aim of removing especially

microorganic pollutants. Regarding the three microorganic compounds used as indicator

substances in this project, activated carbon showed very high degrees of removal of PFOS

(98%) and PFOA (89%), whereas there was a negative removal of Bisphenol A. The latter is

likely to be due to analytic errors. For ozone treatment removal rates were also relatively high,

64 and 70 % for PFOS and PFOA respectively, and a removal of 60% was seen for Bisphenol

A. Although the concentrations in the treated permeate was still well above the EQS limit for all

three microorganic substances tested, ozone and especially activated carbon seems to be

promising polishing methods. In this connection it must also be remembered that the effluent

discharge requirements for a given leachate treatment plant would probably be less strict

according to the specific discharge conditions taking the dilution factor in to account.

As the conducted polishing test were carried out as “full throttle” test, with the sole aim of testing

the potential of the processes, the applied ozone doses and activated carbon retention time was

relatively high, and would probably result in unrealistic high opex, if this were to be applied in a

full scale. Hence further work is needed to optimize operational parameters, and also to look at

the removal of a wider range of microorganic substances.

None of the tested processes aims at removal of salts. EQS-values for chloride and sulphate in

case of discharge to inland surface waters are 40 mg/l and even less in some cases, this is 10-

20 times lower than the concentrations in raw leachate, and the tested treatment processes will

not remove chloride to any considerable degree. As mentioned above it might be that the

effluent criteria for a specific case might be less strict because of the dilution factors and other

considerations. In this connection it should be mentioned that treated municipal wastewater will

typically have concentrations of chloride in the range of 300-500 mg/l. However if for a given

case it turns out that removal of salts is required the only realistic polishing processes would

seem to be reverse osmosis (RO). If RO was to be included in the treatment train, it would

probably substitute activated carbon and ozonation. The permeate from the RO process would

probably comply with all EQS-values, and the permeate could therefore be discharged directly

to an inland surface water recipient in most if not all cases. However, in addition to a probably

higher treatment cost for RO than for activated carbon or ozonation, RO poses a serious

drawback in terms of the generation of a concentrate (10-30% of the influent volume), that must

be further handled. Further work should therefore also include testing of RO-treatment of MBR

permeate, and solutions to the handling of concentrate should be considered. Considerations

should include the use of evaporation ponds at the landfill as a cost efficient method.

37

9 Conclusion

From the results of the chemical analysis of raw leachate for traditional wastewater parameters,

metals and organic micro pollutants the following main conclusions can be drawn in relation to

discharge limit values or the Environmental Quality Standards (EQS):

Concentrations of COD, ammonia-ammonium-N, total phosphorous, total nitrogen,

chloride, sulfate, barium, cobalt, copper, nickel, zinc, PFOS and bisphenol A will exceed

the discharge limit values or the EQS-values at least ten times.

The concentrations of suspended solids, arsenic, lead, cadmium, chromium,

manganese, vanadium and the organic micro pollutants DEHP, pyrene, octyl- and

nonylphenols in the raw leachate were also measured in concentrations above the

discharge limit values or the EQS-values. For the metals lead and cadmium, the

dissolved concentrations in the raw leachate will probably not exceed the EQS.

The screening of the first sample of the raw leachate for metals and organic micro

pollutants indicated, that concentrations of phenols, hydrocarbons, aromatic

hydrocarbons, polyaromatic hydrocarbons (except pyrene), phthalates (except DEHP),

brominated flame retardants and PCB where generally low and did not exceed the EQS

(if it exist).

The concentration of the analyzed components showed generally the same level in all

three samples of raw leachate, except for PFOS/PFOA and bisphenol A.

The following main conclusions can be drawn from the conducted laboratory and pilot tests:

The examined leachate showed a low degradability of COD

The degree of inhibition of nitrification varied from high to low in the two different

samples of leachate that was tested

Aeration of two different samples of leachate showed 50% removal of dissolved iron for

one of the samples and 100 % increase in dissolved iron for the other sample

Addition of NaOH resulted in a high degree of precipitation through formation of large

flocs. The size of the formed flocs increased with the quantity of NaOH added. A more

or less clear supernatant was formed depending on the specific sample of leachate.

In the pilot test on biological treatment of leachate it was found that the VSS/SS-ratio

showed an almost lineary decrease during the test period. This raises a worry as to the

sustainability of long term biological treatment with the composition of the leachate in

question. Nitrification rates of the activated sludge were approximately constant during

the first 2 weeks of the test period. In the last week the nitrification rate dropped

indicating inhibition from the last truck load of leachate.

The membrane filters of the MBR pilot plant were operated with a net flux in the interval

of 28 to 20 LMH, which is considered acceptable under the prevailing conditions.

The COD-removal by the MBR-plant was low (10-30%). This is consistent with the

COD-fractionation tests conducted at DHI. The MBR-system showed full nitrification

with all ammonia converted to nitrate. TP in the effluent was typically in the interval of 5-

10 mg/l. Lead, cadmium and chromium was removed to below the discharge limit

values/EQS for inland surface waters. The concentrations of barium, arsenic and

manganese were also reduced, but the measured concentrations in the outlet from the

MBR treatment were still above the EQS. The concentrations of the organic micro

pollutants PFOS and PFOA were not significantly reduced with the MBR treatment and

38

would still pose a problem with discharge of MBR treated leachate to inland surface

waters.

Activated carbon treatment was shown to almost completely remove absorbance at 254

nm, thereby indicating an extensive removal of COD. Activated carbon treatment

resulted in considerable removal of PFOS with a reduction factor of 31, but the

measured outlet concentration is still around 25 times higher than EQS-value of 0.00065

µg/l.

For ozone treatment it was shown that under the prevailing test conditions more than

60% of the absorbance at 254 nm was removed, indicating a similar degree of COD-

removal. From a visual inspection it could be seen that ozonation completely removed

the yellowish colour of the permeate. The concentration of PFOS was reduced with a

factor 2.6, i.e. ozone was less effective than activated carbon

In relation to the development of a full scale process for treatment of raw leachate with the

aim of discharging the treated leachate to inland surface waters, the following main

conclusions can be drawn:

Pre-treatment based on precipitation through addition of caustic seems interesting.

Further work needs to be done to evaluate the removal of specific compounds, and to

optimize the caustic dose.

Biological treatment based on MBR technology has advantages, but the tests also

indicated some critical issues that must be further addressed. On the positive side it was

shown that the membrane filters can be operated with a good flux and no unusual or

unacceptable fouling/scaling issues. As expected complete removal of particles was

observed, and this is a main advantage in relation to a following polishing stage. Full

nitrification also seems possible, and a number of metals can be removed to a relatively

high extent by adsorption to the activated sludge. On the critical side it was observed

that COD removal and sludge production was rather low, indicating that sustainable

biological treatment might be problematic. Further work should focus on the

development of a concept for sustainable operation of the biological stage which could

include ozone treatment to the MBR influent in order to produce more degradable COD,

and/or addition of external carbon to the biological stage should also be considered.

Polishing processes based on ozonation and especially activated carbon seems to be

promising polishing technologies as high to very very high degrees of removal of the

three indicator microorganics was found. Effluent concentrations were still well above

the EQS-values, but the effluent discharge requirements for a specific case may be less

strict taking the dilution factor in to account. Further work should be done to optimize

ozone dose and retention time for activated carbon treatment and also to look at the

removal of a wider range of microorganic substances.

Comparison of concentrations of chloride in raw and treated leachate with the

corresponding EQS-value, shows that salt removal could be necessary in specific

cases. In such cases RO-treatment seems to be the only realistic polishing process that

can be applied. RO would generate a concentrate (10-30% of the influent volume), that

must be handled in a cost efficient and sustainable way. Further work should therefore

also include testing of RO-treatment of MBR permeate, and solutions to the handling of

concentrate should be considered.

39

10 References

/1/ Miljøstyrelsen, Statutory Order No. 1022 of 25/08/2012 on environmental quality

standards for water bodies and requirements for the discharge of pollutants into rivers,

lakes or the sea. (Bek. om miljøkvalitetskrav for vandområder og krav til udledning af

forurenende stoffer til vandløb, søer eller havet, nr. 1022 af 25/08 2010)

/2/ DIRECTIVE 2013/39/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of

12 August 2013 amending Directives 2000/60/EC and 2008/105/EC as regards priority

substances in the field of water policy

/3/ COHIBA, WP3 INNOVATIVE APPROACHES TO CHEMICAL CONTROLS OF

HAZARDOUS SUBSTANCES - Results from chemical analysis, acute and chronic toxicity

tests in Case Studies, Danish National Report

/4/ AV Miljø, Landfill Aftercare – Shredder waste and mixed waste, Report prepared by DHI

for AV Miljø, July 2011

40

APPENDICES

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APPENDIX A – Renosyd, Landf i l l leachate

t reatment (GBB-lab and pi lot test)

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