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