B k d d i iBackground and opportunities for nanotechnology in waterfor nanotechnology in water treatment and supply
Nigel J D Graham
Environmental and Water Resource Engineering (EWRE), Imperial College London
Department of Civil andDepartment of Civil and Environmental Engineering
• 45 Permanent Academic Staff(5 F ll R l A d f E )(5 Fellows Royal Academy of Eng)
• 400 Undergraduate students (4 year M.Eng)
• 300 M t t d t (1 M S ) 95 i EWRE• 300 Masters students (1 year M.Sc) – 95 in EWRE
• 100+ PhD students – 25+ in EWRE
• Leading ‘Civil Engineering’ Department in the UK in Research (UK Gov’t Research Assessment 2008)
• Member of Network with European Engineering Universities• Member of Network with European Engineering Universities –IDEA league (Delft, Paris, Zurich, Aachen)
• R h d t d t h ith T i h U i it HIT d HK• Research and student exchange with Tsinghua University, HIT, and HK Universities (PolyU, HKU, HKUST)
EWRE Section - Environmental and WaterEWRE Section - Environmental and Water Resource Engineering
R h ThResearch Themes
Integrated management of water and wastes in the natural and the built environments
EWRE Section - Environmental and WaterEWRE Section - Environmental and Water Resource Engineering – Nigel Graham
Research Areas:Unit processes in water / wastewater treatment ( id i l i di i fl i(oxidation, coagulation, sedimentation, flotation, filtration adsorption, disinfection)
W t di t ib ti t ( ti l d i l kWater distribution systems (optimal design, leakage measurement & control, water quality, transient behaviour)
Research Interests:• Fundamental basis of treatment processes• Fundamental basis of treatment processes• Process modelling and simulation• Modifications and new developments
Other expertise in Imperial College LondonOther expertise in Imperial College London
• London Centre for Nanotechnology – UCL / Imperial(I i l Ch i t M t i l Ph i Ch E Bi d E )(Imperial: Chemistry, Materials, Physics, Chem Eng, Biomed Eng)
• Dept Chemical Engineering – Prof Li Kang (membranes), Dr Klaus Hellgardt (reaction systems), Prof Geoff Kelsall (electrochemistry), Prof Paul Luckham (polymers)
• Dept Bioengineering – Dr Danny O’Hare (sensors)
• NaNoRisk Initiative – Imperial / Natural History Museum
NaNoRISK (Nanotoxicology Research in South Kensington) is a joint NaNoRISK (Nanotoxicology Research in South Kensington) is a joint venture between Imperial College and the Natural History Museum to:• study of nano-sized materials in relation to the environment and human health.• establish multidisciplinary research in the hazard and risk of nanomaterials and to develop safe applications on nanotechnology
Principal Components of Water Supply
Ref: I. Stoianov
Water Treatment
Current challenges – water quality & treatment
1. Deteriorating / variable source water quality • Changing land use and climate (eg. organic colour, algal blooms)
I t ifi d i lt l ti ( i i t i t • Intensified agricultural practices (eg. microorganisms, nutrients, pesticides)
• Urban runoff/wastewater discharges (eg. nutrients, pharmaceutical & healthcare products) p )
Algae blooms Organic (humic) colour
Current challenges – water quality & treatment
2. Organic micropollutants Di i f ti b d t ( HAA NDMA th B I DBP )• Disinfection by-products (eg. HAAs, NDMA, other Br-, I-,DBPs)
• New pesticides (eg. metaldehyde)• Pharmaceutical & healthcare products (eg. antibiotics, X-ray contrast
media anti-inflammatories endocrine disruptors) media, anti-inflammatories, endocrine disruptors)
3. Operational pressures • Need for greater reliability, automation, on-line control• Less chemicals and energy consumption (new Gov’t CO2 targets)• Less residual/waste materials (possible reuse / conversion to new
t i l )materials)
Current challenges – water distribution
1. Maintaining water quality in distribution system • Minimisation of sediments, corrosion, biofilms
A id f t i t / bili ti f di t & bi fil• Avoidance of re-entrainment /mobilisation of sediments & biofilms• Greater monitoring (eg. use of in-flow sensors)• Better modelling (eg. Predict water age, chlorine residuals, DBPs)
2. Operational performance needs • Real-time pressure & flow acquisition and communication (eg. 1 sec
li GPRS)sampling, GPRS)• Pressure, leakage and energy management (eg. pump scheduling,
dynamic PRVs, optimal zoning)• Risk-based decision support systems (eg alarm prioritization intervention Risk based decision support systems (eg. alarm prioritization, intervention
assessments)
Current research – Examples
Developments in water treatment - combined processes
• New chemicals for combined oxidation and coagulation (Ferrate)
• Electrocoagulation-flotation
Water quality and distribution – real-time monitoring
• Development of wireless sensor networks
• Evaluation of in-line water quality monitor
• Effect of pressure transients on water quality
Combined oxidation and coagulation
Currently, separate processes for pre-oxidation and coagulation
Pre-oxidation (alternatives: ozone, chlorine, permanganate)
Coagulation (addition of aluminium or ferric salts)
2Ferrate (FeO42-)
Coagulant products Oxidation
CH3 Bisphenol A (BPA) ibl d i
1 .0
OH C
CH3
OH Bisphenol A (BPA) – possible endocrine disrupting compound (Prof XZ Li, HK PolyU)
0 7
0 .8
0 .9
Model fitting by MatLab least squares
Experimental results (data points)
0 .5
0 .6
0 .7
2 1/Cb0
1 :1Ferrate : BPA molar ratio
0 .3
0 .4
4 :1
3 :1
2 :1Cb/
0 .0
0 .1
0 .25 :1
Measured Rate Constants (dissociated BPA):0 100 200 300 400 500 600
T im e (s )
Measured Rate Constants (dissociated BPA):kHFeO4- = 1190 M-1s-1 kFeO42- = 293 M-1s-1
Ferrate Coagulation Performance
• PDA – Photometric Dispersion Analyzer (optical method)
• M t itt d li ht • Measures average transmitted light intensity (dc value) and the RMS value of the fluctuating component of flow
• RMS or RMS/dc ratio is a measure of • RMS or RMS/dc ratio is a measure of particle aggregation – Flocculation Index (FI)
COMPUTERREACTOR
MIXER
PDAMETERING PUMPDATA LOG
Ferrate Coagulation Performance (Humic acids, pH 5)
90%
100%
0.9
1
90%
100%
0.9
1
Ferric Chloride (reference) Ferrate
50%
60%
70%
80%
0 5
0.6
0.7
0.8
dex
Max
Floc Index
% TOC removal
50%
60%
70%
80%
0 5
0.6
0.7
0.8
ex M
ax
20%
30%
40%
50%
0.2
0.3
0.4
0.5
Floc
Ind
20%
30%
40%
50%
0.2
0.3
0.4
0.5
Floc
Inde
Floc Index
0%
10%
0
0.1
0 50 100 150 200Fe dose (microMole)
0%
10%
0
0.1
0 50 100 150 200Fe dose (microMole)
% TOC removal
( )
• Similar coagulation performance (FImax), but greater Fe dose with Ferrate
• Much broader coagulation range – extending into higher Fe dose rangeMuch broader coagulation range – extending into higher Fe dose range
Development of a Combined Ferrate / Photo catalyticDevelopment of a Combined Ferrate / Photo-catalytic Process )
Previous studies jointly with Prof X Z Li, HK Polytechnic University
Development of a Combined Ferrate / Photo catalyticDevelopment of a Combined Ferrate / Photo-catalytic Process )
Development of a Combined Ferrate / Photo catalyticDevelopment of a Combined Ferrate / Photo-catalytic Process )
Electro-coagulation / Flotation Process
Water quality and distribution
Water Distribution Networks
Need for real-time monitoring of system:Pressure, flow rate, water levels, equipment status, water quality
Benefits:B tt d t di f t• Better understanding of system
• Optimization of operation – less energy, cost• Reduction of leakage, bursts, water quality problemsL t lif ti• Longer asset lifetime
Current Interest:• Transmission mains• Pump condition, operation of control valves
• Impact of pumps and valves on water quality – transient effectspac o pu ps a d a es o a e qua y a s e e ec s
Water quality changes in pipes
Pipe Wall
Compounds in bulk (ammonia, manganese, humic material, etc)
Pipe Wall
slime from biofilm (temp, hydraulics, shear stress)
corrosion products (pH temp hydraulics shear stress
microbial products (temperature, hydraulics, shear stress)
Compounds corrosion products (pH, temp, hydraulics, shear stress, conductivity, dissolved oxygen, alkalinity, hardness)released from
wallbiofilm on wall scour (shear stress)
wall reactions
Parameters measured are with red.Ref: A. Aisopou and I. Stoianov
Evaluation of a commercial multi parameter waterEvaluation of a commercial multi-parameter water quality sensor probe
Intellisonde (Intellitect Ltd.)
free & total chlorine
Laboratory evaluation
free & total chlorine, colour, turbidity, conductivity, pH, ORP, temperature
8 months continuous testing period g p1 min sample intervalsAssess: accuracy, sensitivity, response time, reproducibilitysensors tested: chlorine, turbidity, colour, conductivity,sensors tested: chlorine, turbidity, colour, conductivity,
temperature, pH
Ref: A. Aisopou and I. Stoianov
Evaluation of a commercial multi parameter waterEvaluation of a commercial multi-parameter water quality sensor probe - Conclusions
Pro:Limited number of sensors available in the market.Laboratory tests confirm potential to provide useful data.
Pro:
Good dynamic response. Can capture trends and changes from the baseline values.
Detection limits within the range of relevant EPA & EU standards.
The accuracy of the absolute value is uncertain.Frequent calibration and maintenance required.
Con:
Frequent calibration and maintenance required.Sensors can exhibit total failure or lose sensitivity with time due to
bio-fouling & salt deposition (requiring replacement of sensors).Challenges for interpretation of acquired dataChallenges for interpretation of acquired data.
Calcium carbonate deposits
Ref: A. Aisopou and I. Stoianov
Opportunities for N-technology research
Beneficial Properties: Physical: size, specific surface area, hydraulicChemical: catalytic, photo-catalytic, photo-active, redoxBiological: engineered biopolymers, etc
Current research areas: • Nano-metallic particles – for disinfection (Ag)• Multi functional magnetic nanoparticles for disinfection catalysts• Multi-functional magnetic nanoparticles – for disinfection, catalysts, adsorbents• Visible light photocatalytic particles – for oxidation• Nano-coatings on high surface area/low cost substrates – various• Nanotechnology based membranes – desalination (fouling resistance)• Sensor applications• Sensor applications
Opportunities for N-technology research
Wider technology requirements:
• Cost-benefit balance• Adaptation of existing processes• Low energy (e.g. solar powered?)• Low residual production (quantity and non problematic nature)• Low residual production (quantity and non-problematic nature)
Additional research areas – occurrence and fate of N-materials:
• Poor understanding/knowledge of N-materials in typical water/wastewater treatment• Lack of monitoring methods• Lack of monitoring methods• Poor understanding of health implications and risks• Evaluation of new technologies to control N-materials / minimize exposure risks