Background and opportunities

Transcription

1 Background and opportunities i for nanotechnology in water treatment and supply Nigel J D Graham Environmental and Water Resource Engineering (EWRE), Imperial College London

2 Department of Civil and Environmental Engineering 45 Permanent Academic Staff (5 Fellows Royal Academy of Eng) 400 Undergraduate students (4 year M.Eng) 300 Masters students t (1 year MS 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 IDEA league (Delft, Paris, Zurich, Aachen) R h d t d t h ith Ti h U i it HIT d HK Research and student exchange with Tsinghua University, HIT, and HK Universities (PolyU, HKU, HKUST)

3 EWRE Section - Environmental and Water Resource Engineering Research Themes Integrated management of water and wastes in the natural and the built environments

4 EWRE Section - Environmental and Water Resource Engineering Nigel Graham Research Areas: Unit processes in water / wastewater treatment (oxidation, i coagulation, sedimentation, i flotation, filtration adsorption, disinfection) Water distribution ib ti systems (optimal design, leakage measurement & control, water quality, transient behaviour) Research Interests: Fundamental basis of treatment processes Process modelling and simulation Modifications and new developments

5 Other expertise in Imperial College London London Centre for Nanotechnology UCL / Imperial (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

6 Principal Components of Water Supply Ref: I. Stoianov

7 Water Treatment

8 Current challenges water quality & treatment 1. Deteriorating / variable source water quality Changing land use and climate (eg. organic colour, algal blooms) Intensified agricultural l practices (eg. microorganisms, i nutrients, t pesticides) Urban runoff/wastewater discharges (eg. nutrients, pharmaceutical & healthcare products) Organic (humic) colour Algae blooms

9 Current challenges water quality & treatment 2. Organic micropollutants Disinfection i 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) 3. Operational pressures Need for greater reliability, automation, on-line control Less chemicals and energy consumption (new Gov t CO 2 targets) Less residual/waste materials (possible reuse / conversion to new materials)

10 Current challenges water distribution 1. Maintaining water quality in distribution system Minimisation of sediments, corrosion, biofilms Avoidance of re-entrainment t /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 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)

11 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

12 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)

13 Ferrate (FeO 2-4 ) Coagulant products Oxidation

14 HO CH 3 C OH Bisphenol A (BPA) possible endocrine CH 3 disrupting compound (Prof XZ Li, HK PolyU) Experimental results (data points) 0.8 Model fitting by MatLab least squares /C b0 C b / :1 21 :1 3:1 4:1 5:1 Ferrate : BPA molar ratio 0.0 Measured Rate Constants (dissociated BPA): k Time (s) HFeO4 - = 1190 M -1 s -1 k FeO4 2- = 293 M -1 s -1

15 Ferrate Coagulation Performance PDA Photometric Dispersion Analyzer (optical method) 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 particle aggregation Flocculation Index (FI) MIXER REACTOR COMPUTER METERING PUMP PDA DATA LOG

16 Ferrate Coagulation Performance (Humic acids, ph 5) Ferric Chloride (reference) Ferrate 1 100% 1 100% % % Floc Ind dex Max % Floc Index 70% % TOC removal 60% 50% 40% 30% 20% 10% 0% Fe dose (micromole) Floc Inde ex Max % 70% 60% 50% 40% 30% Floc Index 20% % TOC removal 10% 0% Fe dose (micromole) Similar coagulation performance (FI max ), but greater Fe dose with Ferrate Much broader coagulation range extending into higher Fe dose range

17 Development of a Combined Ferrate / Photo-catalytic Process ) Previous studies jointly with Prof X Z Li, HK Polytechnic University

18 Development of a Combined Ferrate / Photo catalytic Development of a Combined Ferrate / Photo-catalytic Process )

19 Development of a Combined Ferrate / Photo catalytic Development of a Combined Ferrate / Photo-catalytic Process )

20 Electro-coagulation / Flotation Process

21 Water quality and distribution Water Distribution Networks Need for real-time monitoring of system: Pressure, flow rate, water levels, equipment status, water quality Benefits: Better understanding di of system Optimization of operation less energy, cost Reduction of leakage, bursts, water quality problems Longer asset lifetime Current Interest: Transmission mains Pump condition, operation of control valves Impact of pumps ps and valves on water quality transient effects ec

22 Water quality changes in pipes Pipe Wall Compounds in bulk (ammonia, manganese, humic material, etc) biofilm on wall Compounds released from wall microbial products (temperature, hydraulics, shear stress) slime from biofilm (temp, hydraulics, shear stress) corrosion products (ph, temp, hydraulics, shear stress, conductivity, dissolved oxygen, alkalinity, hardness) scour (shear stress) wall reactions Ref: A. Aisopou and I. Stoianov Parameters measured are with red.

23 Evaluation of a commercial multi-parameter water quality sensor probe Intellisonde (Intellitect Ltd.) Laboratory evaluation free & total chlorine, colour, turbidity, conductivity, ph, ORP, temperature 8 months continuous testing gperiod 1 min sample intervals Assess: accuracy, sensitivity, response time, reproducibility sensors tested: chlorine, turbidity, colour, conductivity, temperature, ph Ref: A. Aisopou and I. Stoianov

24 Pro: Evaluation of a commercial multi-parameter water quality sensor probe - Conclusions Limited number of sensors available in the market. Laboratory tests confirm potential to provide useful data. Good dynamic response. Can capture trends and changes from the baseline values. Detection limits within the range of relevant EPA & EU standards. Con: The accuracy of the absolute value is uncertain. 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 data. Ref: A. Aisopou and I. Stoianov Calcium carbonate deposits

25 Opportunities for N-technology research Beneficial Properties: Physical: size, specific surface area, hydraulic Chemical: catalytic, photo-catalytic, photo-active, redox Biological: engineered biopolymers, etc Current research areas: Nano-metallic particles for disinfection (Ag) 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

26 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) Additional research areas occurrence and fate of N-materials: Poor understanding/knowledge of N-materials in typical water/wastewater treatment Lack of monitoring methods Poor understanding of health implications and risks Evaluation of new technologies to control N-materials / minimize exposure risks