Tomio Suzuki(Non Profit Organization, Institute of Ecological Engineering, Japan)

(E-mail: suzukit@wave.plala.or.jp)

Yutaro Anzai(Shinshu-University, Japan)

Akito Matsumoto(Shinshu-University, Japan)

(E-mail: amatsu1@shinshu-u.ac.jp)

Groundwater and soil pollution with nitrate nitrogen by land disposal of wastewater,

and a trial measure against the issues

1

6. An experimental result of removing NO3-N using

“the Lauric-Acid-Soil system” (LAS system)

2. Groundwater pollution with nitrate nitrogen (NO3-N) by land disposal of wastewater

4.How long does NO3-N remain in soil under the natural condition?

3. Soil pollution with NO3-N by land disposal of wastewater

5.How to remove NO3-N?

2

1. Back ground

Contents of this presentation

1. Back ground

Following issues are worried in these areas

1)Groundwater pollution

2)Soil pollution

Measures against these issues are required from the viewpoint of sustainable development.

These issues are worried not only in case of the dumping of raw human waste but also that of treated water, because some kinds of pollutants are usually still remaining even in the treated water.

3

Wastewater such as human waste has been dumped into the ground at most of remote areas.

4

The reason why NO3-N is taken in this presentation

1)The ill effect of NO3-N on human beings Methemoglobinemia symptom may be caused by the intake of water

containing NO3-N.

2) The value of the guidelines of NO3-N for drinking water quality The value of the guidelines for drinking water quality is set at 50 mgNO3

-/L (about 11 mgNO3-N/L) by the World Health Organization (WHO)*.

3) Monitoring results of groundwater quality in Japan1)

The exceeding ratio of NO3-N against the environmental quality standard of groundwater (EQSgw)* has been showing the highest value among the 28 standard items of the EQSgw in Japan.

*The value of the WHO guidelines is set as a sum of nitrate ion (NO3-) and nitrite ion (NO2

-), and that of the EQSgw in Japan is set as a sum of NO3-N and nitrite nitrogen (NO2-N) . However, only NO3-N is taken in this presentation in order to simplify the explanation.

2. Worries of groundwater pollution with NO3-N by land disposal of wastewater

Wastewater(A)（mg/L）

Leachate(B)（mg/L）

Removal efficiency(A-B)/A☓100（%）

Biochemical Oxygen Demand (BOD) 53 0.6 98

Total Phosphorus (TP) 9.8 0.03 99

Ammonia Nitrogen (NH4-N) 125 8.6 93

Nitrate Nitrogen (NO3-N) 0.20 87 -430

Total Nitrogen (TN) 132 97 26

(The soil was volcanic ash soil. The permeation distance of the most of leachate through soil was 65cm)

2)Concentration of NO3-N increased remarkably in the leachate by theoxidation of NH4-N.

1)Both BOD and TP were removed more than 90% in the leachate.

Results are summarized as follows.

Table 1 Comparison of water quality between wastewater and its leachate through soil2),3)

5Worries of groundwater pollution with NO3-N

Research methods

1) Soil at a wastewater permeated area was dug twice, at the time of 2months and 17 months after the end of wastewater loading, in the rangeof 200cm deep, 600cm wide crossing a trench by which wastewater hadbeen loaded for 5 years.

2) Soil samples were collected twice, at the time of 2 months and 17 months after the end of wastewater loading, from each of corresponding50cm mesh points in the vertical soil wall of the wastewater permeatedarea (Fig.1 in the slide 7).

3) The concentration of NO3-N in the soil obtained from the twice researcheswere compared at each corresponding sampling point with that of controlarea (Fig.2 in the slide 8).

3. Soil pollution with NO3-N by land disposal of wastewater

Note that the investigated facility differs from the one shown in Table 1.

6

Water impervious layer

Fig.1 An outline of the soil sampling points in the wastewater permeated area 3),4)

7

300 250 200 150 100 50 0 50 100 150 200 250 300

0 ○

De

pth（

cm）

50 ● ● ● ● ● ● ● ● ● ● ● ● ● ●

100 ● ● ● ● ● ● ● ● ● ● ● ● ● ●

150 ● ● ● ● ● ● ● ● ● ● ● ● ● ●

200 ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Control area

Watering tubeTrench

Ground surface

Dots (●and ●) denote soil sampling points.

Horizontal distance from the trench（cm）

50100

150200

0

50

100

150

200

30

02

00

10

0

0

10

0

20

0

30

0

Co

ntr

ol0

50100

150200

0

50

100

150

200

30

02

00

10

0

0

10

0

20

0

30

0

Co

ntr

ol

●The concentration of NO3-N in the soil increased remarkably by wastewaterpermeation as compared with that of control area.

● Increased No3-N in the soil rarely decreased even passing through 15months under the natural condition except the root zone at a depth of 50cm.

Concentration of NO3-N in the soil at the time of 2 months after the end of

wastewater loading (NO3-N2M)

Concentration of NO3-N in the soil at the time of 17 months after the end of

wastewater loading (NO3-N17M)

Fig.2 Comparison of the concentration of NO3-N in the soil between NO3-N2M and NO3-N17M

3),4)

An arrow ( ) denotes the point of wastewater loading by the trench

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Fig.3 Relation of NO3-N concentration in the soil between NO3-N2M

and NO3-N17M at the corresponding sampling points3),4)

y = 0.78x + 4.1r = 0.93

0

20

40

60

80

100

120

0 50 100 150

NO3-N 2M(mg/kg)

NO

3-N

17

M(m

g/k

g)

The data of the root zone at a depth of 50cm were omitted taking into account of the special condition of this area that the decrease of NO3-N based on the absorption by plants might be proceeding.

9

Following results are obtained from Fig.3 3),4) in the slide 9.

1) The concentration of NO3-N in the soil decreased nearly in a same ratio at each correspondingsampling point during 15 months.

2) It is considered that the value, 0.78 shown in the regression equation in Fig.3, shows thedecreasing coefficient of NO3- N in the soil during every 15 months under the natural condition.

3) It is estimated from the equation below that more than 10 years would be required in order todecrease the amount of NO3-N in the soil of wastewater permeated area to that of control area.

∑ dN2M☓P0.8n=∑ dNcd=100

200

d=100

200

P(=0.78): Natural decreasing coefficient of NO3-N in thesoil during every 15 months

n: Years required to decrease the amount of NO3-N in the soil of the wastewater permeated area to that of control area

∑ d N2M: Amount of NO3-N contained in the soil of thewastewater permeated area, 200cm deep,650cm wide and 100cm thick, at the time of 2months after the end of wastewater loading

200

d=100

∑d NC: Amount of NO3-N contained in the soilof the control area, 200cm deep, 650cm wide and 100cm thick

200

d=100

4.How long does NO3-N remain in soil under the natural condition?

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5. How to remove NO3-N?

• Under coexistence of denitrifying bacteria→Denitrifying bacteria are commonly living in soil under the natural condition

• Under a proper temperature→Desirable more than 10℃• Under a proper pH →Most of soil would have proper condition• Under an anoxic condition→A submerged soil condition would

be available• Under coexistence of an effective Hydrogen Donor (HD) →

Searches of effective HDs are required

It is well known that NO3-N would be removed as N2

under such proper conditions shown below.

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A denitrifying method for wastewater treatment using soil would be established under the coexistence of an effective HD.

Matters to be considered in the searching of effective HDs

• To work effectively as a HD

• Not to induce a secondary pollution by the HD itself

• Low maintenance in operation

• Low cost in operation

• Harmless for human beings

A series of Higher Fatty Acids (HFAs) was examined for the searching of effective HDs considering the factors described above.

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An anticipated denitrification

effectAn anticipated anti secondary pollution effect

Smal

l

Smal

l

Larg

e

Larg

e

Which HFA does it work best as an effective HD?

Tests for the searching of effective HDs were performed among 5-kind HFAs from both sides, a denitrification and an anti secondary pollution effect, anticipated from their water solubility.

Fig.4 Water solubility of 5-kind HFAs at 20℃5)

13

0

5

10

15

20

capricacid

lauricacid

myristicacid

palmiticacid

stearicacid

Wat

er s

olu

bili

ty (

mg

/10

0g)

Collection of interstitial water

Fig.5 An experimental device and the method for the searching of effective HDs using HFAs

A mixture of one kind of HFAs and soil

( HFA : Soil = 1 : 10,by weight)

A cylindrical filter

Research methods●Each of 5-kind HFAs was mixed with soil at a ratio of 1(HFA) to 10(soil) by weight.●Each mixture of 5-kind HFAs was submerged with 50mgNO3-N /L solution

and was incubated at a temperature of 5, 10, 15 and 20℃, respectively.●Each interstitial water was collected and analyzed after 7-day incubation.●A control, i.e. soil without HFAs, was examined in the same manner .

A solution of 50mgNO3-N/L

14

0

10

20

30

40

50

60

capricacid

lauricacid

myristicacid

palmiticacid

stearicacid

control

5℃

TN (

mg/

L)

0

10

20

30

40

50

60

capricacid

lauricacid

myristicacid

palmiticacid

stearicacid

control

TN (

mg/

L)0

10

20

30

40

50

60

capricacid

lauricacid

myristicacid

palmiticacid

stearicacid

control

15℃

TN (

mg/

L)

0

10

20

30

40

50

60

capricacid

lauricacid

myristicacid

palmiticacid

stearicacid

control

TN (

mg/

L)

10℃

20℃

Fig.6 Analytical results of TN concentration in the interstitial water obtained from the research shown in the slide 146)

Lauric Acid (LA) was the most effective HD among 5-kind HFAs under the experimental condition described in the slide 14.

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SP3*, HRT**=34h

SP2*, HRT**=23h

SP1*, HRT**=12h

Substrate (a solution of 50mgNO3-N /L)Denitrified water

A pump

Over flow

Soil

LA ： Soil=1：9 mixture (by weight)

A submerged and anoxic condition

Fig.7 A schematic diagram of a continuous denitrifying device under a submerged soil condition using the LAS system

*SP1, 2 and 3 show the sampling points of denitrified water.**HRT shows the hydraulic retention time in the column.

●Soil was mixed with LA in a ratio of 1(LA) to 9(soil) by weight and the mixture was packed at L1 under the soil layer, L2 and L3.

●A solution of 50mgNO3-N /L was led into the column from the bottom and was passed through itupward in order to maintain the device an anoxic condition.

●Denitrified water was collected from each sampling point (SP1-3).●The temperature had been kept at 20℃.

L1

L2

L3

A denitrification and HD supply-utilizing zone

A denitrification and HD utilizing-removing zone

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Denitrified water

0

10

20

30

40

50

60

Substrate SP1 SP2 SP3

TN

TOC

Fig.8 Changes of the average concentration of TN and TOC during one month in the substrate and the denitrified water under the use of the LAS system

Supplied TN (a solution of 50mgNO3-N /L ) was removed 90% within 34h at SP3.

The secondary pollution based on the HD was scarcely observed keeping the concentrationof Total Organic Carbon (TOC) in the denitrified water at SP3 less than 5mgC/L.

Most of increased TOC at SP1 was supplied as LA ion isolated from LA by the action of OH-

generated by denitrification, and was removed at SP2-SP3 as a HD in denitrification .

Additionally,

6. An experimental result of removing NO3-N using the LAS system

17Denitrified water

TN, T

OC

(m

g/L

)

Summar

Both BOD and TP were removed more than 90%, however NO3-N increased remarkably in the leachate by land disposal of wastewater .

Concentration of NO3-N in the soil increased at the wastewater permeated area, and it was estimated that the increased NO3-N would remain in the soil more than 10 years under the natural condition.

Supplied TN as NO3-N was removed about 90% within 34h using the LAS system keeping the concentration of TOC derived from the HD less than 5mgC/L.

Field researches on land disposal of wastewater and a laboratory research on denitrification using the LAS system were performed.

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Taking into account of these results , it is expected that the LAS system would be applied to a system for removing most of TOC(or BOD), TP and TN in land disposal of wastewater .

Results obtained are summarized as follows.

Improvements on better performance for removing of both TN and TOC will be required.

Developments of techniques for the practical use will be required.

Verification of the long term field test under the practical use will be required.

An improvement on a easy removing method of N2

generated by denitrification will be required .

An improvement on a easy supplying method of the HD will be required .

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References

1)Ministry of the environment, Japan (2014) Monitoring results of groundwater quality in FY 2012,

p. 6 (Outline edition, in Japanese).

2)Suzuki, T., Katsuno, T. and Yamaura, G (1992) Land application of wastewater using three types of

trenches set in lysimeters and its mass balance of nitrogen, Water Research, 26, 1433-1444.

3)Suzuki, T. (1993) Land application of wastewater, in “Encyclopedia of environmental control

technology” (Edited by Cheremisinoff, P. N.), Vol.9, pp. 641-706, Gulf publishing Company, Houston.

4)Suzuki, T. and Yamaura, G. (1989) Natural recovery of chemical components accumulated in soil by

wastewater application, Water Research, 23, 1285-1291.

5) Japan oil chemists’ society (2001) Lipids and surfactants, The handbook of oil chemistry, 4th Ed.,

pp. 302-303, Maruzen, Tokyo (in Japanese).

6)Suzuki, T., Ishikawa, T. and Furihata, A. (2002) Denitrification of nitrate nitrogen using soil mixed

with solid fatty acid under flooding condition, Proceedings of the 36th annual conference of

Japan society on water environment (Okayama, 14-16 March), p. 402 (in Japanese).

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