Transcript of "Brian Clarke on Water Aid (Cafe Scientifique)"
Not Water Aid…… ….but water aid to Rwanda, Aceh, Darfur & UgandaWater Treatment in Emergencies and the Developing World! Brian Clarke Deputy Director Centre for Environmental & Health Engineering (CEHE)Faculty of Engineering & Physical Sciences
Why is water important? What has water ever done for you?• You are over 60% water• Water is in every cell of your body, except in hair and nails• Water dilutes and carries your waste away• Water is used to regulate your temperature
Water Quality• When it comes to water quality, either raw water or potable supplies, always think in terms of physical, chemical and (micro)biological features• It doesn’t look very nice, ughhhh… NTU, SS mg/l or particle size µm?• It doesn’t taste very nice, but….. organic, inorganic, toxic, hazardous, multiple, site testing, sanitary survey?• I feel ill, Cholera Mary’s got me again! water related disease, faecal-oral transmission route
Crisps for breakfast,couldn’t face the full English!!
How do you measure microbiological “contamination”?• Difficult to reliably detect pathogenic microbes in the considerable quantity flow of a community water supply• Pathogens can be present in relatively small numbers and they may be present infrequently or at irregular intervals• Accordingly, searching for pathogens is not a practicable means of monitoring microbiological water quality
Indicator Organism & Delagua Kit• A member of the Coli aerogenes group, Escherichia coli, is used as an indicator organism (not the enterotoxic variant currently affecting Northern Germany!)
If a water is free of E.coli it is assumed that faecal contamination isnon-existent or Microbial monitoring thatthe has been eliminated and in pathogens are notpresent (actually these are thermotolerant coliform assumed faecal!) field?Zero FC/100ml not always an indication of a microbiologically safewater !!!
Water Related Disease• Water borne • Diarrhoea & Dysenteries, Cholera,Typhoid• Water washed • Eye infections. Skin infections• Water based • Shistosomiasis (Bilharzia)• Water related insect vector • Malaria
Water Supply• In some camps Oxfam carried out batch treatment using alum as a coagulant & hypochlorite disinfection• MSF had a fleet of trucks carrying up to 2 million litres of water per day to 68 locations in the campsites, chlorine was added as the trucks left Lake Kivu and, after travelling for 90 - 120 minutes, was suitable for consumption (www Susie Low MSF)
Water Related Disease• People began to get sick, on July 18th 1994 the first cases of cholera were confirmed in Goma town• A laboratory identified the causative organism as Vibrio cholerae 01, biotype El Tor, Serotype Twawa, resistant to affordable drugs such as doxycycline• More than 3,000 cases of cholera were reported the first day
Refugees Return• After 3-4 years the refugees were encouraged to return to Rwanda• Commencing 1996 CEHE had established a pilot plant at Nyabwishongwezi to support DFID funded research• 20,000 refugees and IDPs settled the Northern part of the Akagera Game Park• CEHE advised the UN on the development of a community water treatment system
Slow Sand Filtration• James Simpson constructed slow sand filters for the Chelsea Water Company in London in 1829 and, towards the end of the 19th Century, widespread application of slow sand filtration occurred in Europe• Historically a significant reduction of drinking water transmitted disease was noted in communities supplied with slow sand filtered water ( Rachwal et al, 1996)• CEHE research confirmed that a multistage system of gravel prefilters, slow sand filters and terminal disinfection can provide effective multiple barriers to penetration by pathogens
Slow Sand FilterSupernatant Schmutzdecke Biologically active zone Sand filter Filter Support Underdrainage
Microbiological Performance FabricEnhanced Depth Bacteriophage Polio VirusSlow Sand mm % Reduction % Reduction Filter SSF A 200 98.77 99.93 SSF B 300 99.88 99.99 SSF C 500 99.97 >99.99
Don’t rely on Bio-adsorption! 2-4-D Herbicide Removal
Protection of Slow Sand Filters with Gravel Prefilters• It is recognised that the operational support required for water treatment systems will need to be simple and affordable if they are to obtain widespread acceptance for small community applications in the developing world (Clarke et Al , 1996)• Employing upflow gravel prefilters as a form of pretreatment considerably reduces the risk of the slow sand filter blocking as a result of the surface straining of particles present in the raw water
Multistage Filtration System Multiple Barrier ConceptGravel PrefiltersUpflow 40, 20 & 10 mmnominal gravelDepth say 1.0 m Slow Sand Filters Uniformity coefficient = 2 Sharp sand
River Intake Sampling CEHE Research at Nyabwishongwezi 2002
Abstraction from theRiver Umuvumba andPumping to the Water Treatment Works Four Sedimentation TanksTwo Twin-stage Upflow Gravel PrefiltersFour Fabric Enhanced Slow Sand Filters Supply to 15000Disinfection and Storage people in newin two Clearwater Tanks communities
Nyabwishongwezi Water Treatment Plant immediately after construction
Oxfam Clarifier Application? ~ CEHEassisting Oxfam in Tsunami affected Communities in Aceh, Sumatra
Oxfam Field Upflow Clarifier• Design brief to CEHE o It had to fit in a standard Oxfam tank o It had to handle any water quality o It had to produce up to 10000 litres/hour o It had to be cheap and integrate with other Oxfam kits• Physico-chemical treatment and clarification• Suction side dosing (thanks to MSF, Brussels)
Coagulant Chemistry? (simplified)• Alum + calcium bicarbonate = hydroxyl aluminium floc + calcium sulphate + carbon dioxide Al2(SO4)3 + 3Ca(HCO3)2 = 2Al(OH)3 + 3CaSO4 + 6CO2 destabilisation of colloids combination with hardness to produce floc• In Oxfam field work no laboratory balances are available so a weight of 1100 grams per 1 litre of granular alum is assumed, hence Oxfam Alum Solution, Al2(SO4)3 n H2O ~ “n” a storage issue?
Pump Suction Side Coagulant Dosing Disinfection hypochlorite Clarification dosing T11 Field ClarifierTypical OxfamEmergency Water T45 Storage Tank SupplyTreatment System
Fabric Fabric fixing filter frame Perforated outlet pipe Schematicillustration of an Oxfam Field Floc Blanket Upflow Clarifier Dual inlets for raw water & coagulant from the spiral pipe flocculator
Lamno and Meulaboh• CEHE personnel flew to Banda Aceh to support Oxfam water treatment operations in Lamno & Meulaboh in May• Lamno and Meulaboh are towns that suffered severe damage from the Tsunami• Lamno is about the size of Ventnor and Meulaboh a similar size to Newport• Supervised the construction of an Oxfam physico-chemical system with the assistance of Indonesian colleagues
JCB were very generous and theirmachines were extremely useful…
Pressure Filters• Pressure filters consist of a small pressure vessel with a system for distributing the influent water over the surface area of the filter media and a drainage system for collecting filtered water at outlet• Filters are operated until the headloss across the units reaches a predetermined maximum, typically read on a pressure gauge, or the effluent turbidity reaches a predetermined maximum
Raw water Dirty inlet washwater effluent FilteredWashwater effluent
Issues associated with an Emergency Response• Available water resources for IDPs and refugees?• Raw water quality?• Supply problems• What about the “non technical” aspects of the crisis response? – Community locations – Population figures – Diplomacy – Security – International politics
Contamination of jerry cans before and after cleaning(N.B. the numbers on the diagram represent the specific count).
Electrolysis & Disinfection• All mammals need salt and, accordingly, it is universally available• Electrolysis of salt and water produces sodium hypochlorite• Disinfection by hypochlorite drip is a practical option in the developing world• Disinfection α Cx t ?
Salt type Weight Time of Total Total Chlorine Rotation Chlorine grams seconds mg/l mg/l per gram saltProcessed 1,38 45 2000 1450 1,38 60 2000 1450 Rock 1,04 45 5000 4807 1,11 60 4000 3607 Sea 0,5 45 4000 8000 0,5 60 8000 16000
Sachet Water Treatment Systems• Sachet water treatment products are currently generating interest with UNICEF and the main relief agencies• PUR and Watermaker are the main products currently under consideration by leading Relief Agencies
Interesting Menu?• The specific composition of the PUR sachet was described by Reller et al. (2003) as containing ferric sulphate, bentonite, sodium carbonate, chitosan, polyacrylamide, potassium permanganate and calcium hypochlorite
Ceramic Candle Filters• Ceramic candle filters can remove particulates and micro-organisms from raw surface water at the point of use to provide only drinking water (2litres/day/candle?)• Ceramics typically provide micro-filtration• Surface blocking requires regular hand cleaning
Ceramic Candle Filters Reverse osmosis <0.0001 µm Nano-filtration <0.001 µm Ultra-filtration 0.005-0.01 µm Before Use Micro-filtration 0.2-5.0 µmAfter 1 Run After Cleaning
Ceramic Candle SEM Surface Features CEHE, 2004Stefani Hong Phuk Katadyn
Bacteriophage ~ similar size to pathogens?• The bacteriophages ØX174 and PRD-1 were used in 2006 – 2007 to test the abilities of a selection of ceramic candle filters and sachet treatment products to reduce viral numbers from suspension• The phage ØX174 can be used to “represent” Norovirus, whereas the larger PRD-1 can be used to “represent” both Rotavirus and Adenovirus• Substantial (complete) removal of bacteria but poor removal of viruses ( < 1 log PRD-1 )
The ability to make a good value judgement is the mark of a true Engineer!