Branislav Petrusevski Associate Professor in Water Supply Technology Tel. +31 15 2151785 Fax. +31 15 2122921 e-mail: bpt@ihe ihe.nl IHE-Delft The International Institute for Infrastructural,, Hydraulic and Environmental Engineering Delft The Netherlands Core Activities: - Post-graduate Education (M.Eng Eng.. M. SC. Ph.D.) - Tailor made training (short courses) - Research & Development - Advisory services - Institutional capacity building
New Developments in Arsenic Removal from Groundwater (Health Risks, Occurrence and Removal) B. Petrusevski IHE-Delft 2001
Topics addressed Arsenic -related health-effects effects Locations with Arsenic contaminated groundwater Arsenic removal technologies IHE research on arsenic removal
Arsenic - As / Natural contamination naturally occurring semi-metallic element, widely distributed in the earth s crust (ranked as 52nd between tin and molybdenum), normally combines with S, C, H, O and Cl may be found in water that flows through As-rich rocks.
Arsenic - As / Anthropogenic contamination widely used in many industries in the first half of 20 century (e.g. pesticides, herbicides, raising blueberries, potatoes), still used for decolorizatio of glass, paint manufacturing, treatment of wood, as pharmaceutical (e.g. amoebic dysentery) by-product of smelting ores can be found in surface run-off water and industrial waste water
Chemistry of arsenic exist in groundwater in many oxidation states (+5, +3, +1 and -3) can form many organic and inorganic compounds most common species: arsenate (+5),typically aerobic water arsenite (+3), typically anaerobic conditions, low ph)
Chemistry of Arsenic High solubility in water (e.g. As 2 O 5 1.5 *10 5 µg/l at 16 ºC) As(5+) ionic species negatively charged at ph 5-10 As(3+) ionic species uncharged at ph < 8 As (3+) species more difficult to remove
Arsenic - toxicity toxic to all life; toxicity depends on arsenic form Arsenic form Oral LD50 (mg/kg Body weight) - Sodium Arsenite 15-40 - Arsenic Trioxide 34 - Calcium arsenate 20-800 - Arsenobetaine >10*10^3 exposure toi high levels of arsenic in food or water can cause severe acute intoxication effects: vomiting, diarrhoea, muscle cramps, heart complains, poor appetite, etc. toxic chronice exposure to very low concentrations - slow poison (0.17 µgas/ 10-5 excess life-time skin cancer risk)
Arsenic - toxicity human intake of arsenic mainly from food (e.g. seafood), (primarily low toxicity organic arsenic), drinking water represents the greatest hazard (arsenic present mainly in inorganic form), arsenic in drinking water: no taste, no smell, not visible
Arsenic - toxicity Human carcinogen - risks of: - skin cancer (usually non-fatal), - several internal cancers (lungs, urinary bladder, kidney?, liver??), - estimated cancer mortality risk due to lifetime exposure to drinking water: 50 µg As/L - 1 in 100 adults 500 µg As/L - 1 in 10 adults affects kidney, results in liver failure, cardiovascular, neurological problems, etc. hyperpigmentation, depigmentation, keratosis
Chronicle Arsenic Toxicity clinical characterisation (D.N. Guha et.al. 1999) Clinical characteristics of 248 patients in West Bengal (India) exposed to arsenic contaminated drinking water: 1. Rain-drop pigmentation 94% 2. Weakness 66% 3. Keratosis (sole and palm) 65% 4. Cough 62% 5. Burning sensation of eyes 30% 6. Anemia 44% 7. Hepatomegaly 77% 8. Dyspesia 67% 9. Blackfoot disease 1.2% 10. Skin cancer 2% 11. Kidney cancer 0.4% In total 6 million people exposed arsenic conatminated water in West Bengal only
Guideline values: WHO provisional guideline (1993): 10 µg/l (excess life-time skin cancer risk 6*10-4 ) EC Council Directive: 10 µg/l Canada 25 µg/l, Australia 7 µg/l US 50 µg/l (USEPA proposed 10 µg/l in January 2001 but?? (between 2.000-20.000.WS systems in US will be affected) Bangladesh, India, UK: 50 µg/l
Arsenic contamination of ground waters
Arsenic contamination of groundwater in Bangladesh - 50,000-80,000 out of villages - 3,5 out of 8 million tubewells - 25-60% out of of on 122 million inhabitants at high risk.
WHO described crisis in Bangladesh as the largest mass poisoning in the world
Arsenic contamination of (ground) water Ground water contamination with arsenic is wide spread, occurs in many parts of and may be regarded as a global issue. The arsenic issue will be present at an increasing level in coming years Many more situations with arsenic contamination of (ground) water will be found in the near future New cases will mostly likely in particular be found in Central and Eastern Europe and developing world.
Arsenic Removal Technologies (Enhanced) coagulation followed by floc separation (sedimentation/filtration, membrane filtration) Lime softening Adsorption (activated alumina, ion exchange, GAC) Reverse osmosis, nano filtration Filtration through manganese-green sand filter (with KMnO 4 addition) In-situ subsurface arsenic removal (Copper impregnated) coconut carbon
Enhanced Coagulation Addition of a coagulant (Fe or Al salts), adsorption of arsenic (mainly As5+) onto formed Fe/Al precipitates, floc separation (sedimentation / filtration) Recommended by AWWARF Both Al- and Fe- based coagulants could be used Arsenic removal through adsorption on Fe/Al precipitates As removal efficiency controlled by coagulant type and dose, ph, As speciation, water quality (NOM, Ca, SO 4, PO 4 ) Efficient floc separation prerequisite for good arsenic removal
Enhanced Coagulation Iron coagulants very efficient for As(5+) and partly for As(3+) Al coagulants only efficient for As (5+), oxidation (e.g. prechlorination) needed if As(3+) present typical results (MSc Thesis Rashid 1996) - groundwater with 200 µg As(3+)/l - 8 mg Fe(3+) as FeCl3-95% As removal efficiency advantages enhanced coagulation: - relatively low investment & operational costs - chemicals used widely available / cheap - no breakthrough monitoring needed
Enhanced Coagulation disadvantages enhanced coagulation: - suitable for centralized treatment - formation of large volumes of toxic sludge - skilled operators needed - insufficent removal of As(III) household level set-ups based on: coagulation (incl. oxidation, sedimentation) recommended by some agencies (not practical solution: local unavailability of (multiple)chemicals, inconvenient / complex operation,..)
Lime Softening Addition on lime and CaCO 3 precipitation at high ph 10.5 Flow scheme: aeration-(oxidation)-softening-filtration Efficient for As(5+) removal from hard waters Efficient As (3+) removal requires: pre-oxidation and ph 11 Non consistent As removal efficiency (likely Mg(OH)2 plays an essential role) Disadvantages: - ph correction(s) needed - production of toxic waste - suitable for centralized treatment
Activated Alumina (AA) adsorptive filtration on granular activated alumina; AA is widely available effective for both As(5+) and As (3+) recommended empty- bed detention time EBDT >15 min adsorption capacity / removal efficiency ph dependant (an optimal ph range 6-7.5) - ph adjustment needed relatively low adsorption capacity; competitive adsorption of chloride, sulfate, selenium, fluoride regeneration (caustic soda/ acid) required; 5-10% loss of capacity for each run AA based point of use set-ups applied in practice
Reverse Osmosis / Nanofiltration use of RO and NF for As removal not commonly reported; mostly laboratory and pilot plant studies reported As removal efficiencies: >90% As (5+) and 60-70% As (3+) pre-oxidation needed for As (3+) conversion to As(5+) detrimental for membranes (thin film composite) suitable for centralized and point-of use applications high investment and operational costs low recovery (discharge of reject water (brine) problematic) unsuitable for developing countries (rural areas)
Sub-surface arsenic removal a part of the pumped groundwater (10-50%) is aerated and recirculated back into the aquifer, during water abstraction Fe, Mn and As are adsorbed on the soil grains coated by previously deposited metal oxides, either two wells needed (abstraction/recharge) or one well that operate in an intermittent mode, combines iron, manganese and arsenic removal, cost effective treatment (no need for a complex treatment plant), no (visible) waste production,
Sub-surface treatment - Disadvantages appropriate hydrogeological and geochemical conditions required, either two wells needed (abstraction/recharge) or one well that operate in an intermittent mode, long ripening period no experience with groundwater with higher arsenic concentrations (>40 µg As/l), no experience with process efficiency on longer-term, unknown environmental impact
Available Arsenic Removal Techniques: Suitable for centralised treatment, More effective in As(V) removal, Waste streams (sludge, concentrate), Difficult to meet the standards, Expensive (investment & operation), Complex, inappropriate for rural communities,
Arsenic Research at IHE Focus on As removal technologies Two research lines: a. Development of point-of-use system for drinking water production in developing countries: - 2 completed & 3 on-going MSc. studies & staff research, - adsorptive treatment (ICS and IGAC) - financially supported by VEWIN, NORIT & IHE); b. Centralised treatment for drinking water production and industrial waste water treatment - 5 completed & 3 on-going M.Sc. studies & staff research - based on centralised adsorptive treatment with zeolites and enhanced coagulation - financially supported by industry & IHE.
Point-of-Use Arsenic Removal Systems The only feasible approach for rural areas in many developing countries (e.g. Bangladesh): no piped water supply systems, only 3-4% required for drinking and cooking, arsenic contaminated water safe for other purposes.
Requirements for POU system simple and suitable for use at household level, preferably no chemicals and no use of electricity, manual operation and no sophisticated control, treatment costs should be low, adsorption-based systems likely most suitable.
A. Model water To mirror typical groundwater in Bangladesh: - high buffering capacity (HCO 3 -» 275 mg/l) - ph» 6.8 - Temp» 25 o C; - [As]» 500 mg As/L [both As(III) and As(V)] (only 3% of wells in Bangladesh have As > 500 mg/l) B. As-contaminated groundwater from Hungary
Arsenic adsorbed Selection of adsorbent 100% 80% 60% 40% 20% 0% As(V) As(III) IGAC (Iron coated GAC) Olivine Basalt Sand ICS-1 ICS-2 ICS-3 ICS-4 ICS (Iron Coated Sand) adsorbent dose: 8 g/l; 500 µg As/L; contact time: 8 hrs ICS-5 Adsorbent ICS-6 ICS-7 ICS-8 ICS-9 IGAC-1 IGAC-2
Adsorbents selected for further experiments IGAC (Iron coated GAC) ICS (Iron Coated Sand)
Freundlich adsorption isotherm As(V): y = 1265.9x 0.260 As(III): y = 924.53x 0.418 As(V): y = 279.98x 0.354 As(III): y = 231.37x 0.514 100000 100000 mg As adsorbed/g adsorben 10000 As(V) As(III) mg As adsorbed/g adsorben 10000 1000 As(V) As(III) 1000 10 100 1000 Equilibrium [As]: C e mg/l 100 10 100 1000 Equilibrium [As]: C e mg/l ICS IGAC model water: 1600 µg As/L; contact time: 12 days)
Filtration based POU - Family filter
As removal with family filter Arsenic (III) concentration ( g/l) 500 400 300 200 100 0 Filtrate Feed Water WHO standard Bangladesh standard 0 50 100 150 200 250 Time (days) Adsorbent: ICS, V=950 ml, H-26 H cm, V f = 0.21 m/h
As removal with family filter 50 Arsenic (III) concentration ( g/l) 40 30 20 10 0 Filtrate WHO standard 0 50 100 150 200 250 Time (days) Adsorbent: ICS, V=950 ml, H-26 H cm, V f = 0.21 m/h Feed water: 500 µg As (III)/L
Application of ICS or IGAC Family filter non-optimised family filter with ICS or IGAC has very high As(III) and As(V) removal potential, no electricity, no chemicals, needed, simple and affordable for rural communities, family filter should be optimised and a robust design should be established.. Family filter with 2 L of IGAC or ICS can supply a family in rural Bangladesh with arsenic free water for drinking and cooking for on average 18 months.
Conclusions Presence of arsenic in drinking water presents a serious problem to public health. Chronic exposure to arsenic can cause variety of diseases including skin and internal cancers, black-brown and depigmentation, vascular disorder etc. The full extent of arsenic-related health problems is not yet fully identified and quantified Ground water contamination with arsenic is wide spread, and may be regarded as a global issue with many new cases in the near. future.
Conclusions Available arsenic removal technologies complex, expensive and inappropriate for rural communities. Adsorbent-based Point-of-Use systems appropriate arsenic removal strategy for rural communities in developing countries. Simple filtration based POU Family filter with either ICS or IGAC as a filter media demonstrated high potential for arsenic [As(III) / As (V)] removal. The Family filter with IGAC or ICS is very promising device to alleviate arsenic related problems in rural areas of the developing countries.
Acknowledgement IHE Laboratory staff S.M. Shahidullah (M.Sc. study) Dr. T. Ahsan (photo s) Arsenic-related research at IHE was financially supported by: - VEWIN - Association of Dutch Water Works - SEILOR - NORIT
Goal of the research To develop POU arsenic removal system suitable for rural areas of developing countries Objectives of the study arsenic removal capacity of different adsorbents effect of contact time, ph and As speciation / concentration, preliminary test suitability of different set-ups
Experimental set-ups A. Batch adsorption equilibrium experiments different adsorbents, ph, adsorption time and dosage, arsenic concentration and speciation B. Experiments with POU systems To study As removal potential of very simple setups: tea bag coffee filter family filter
Batch experimental set-up mechanical shaker
Effect of ph on As removal efficiency 100% 100% Arsenic adsorbed 80% 60% 40% As(V) Arsenic adsorbed 80% 60% 40% As(V) As(III) As(III) 20% 4 6 8 10 ph 20% 4 6 8 10 ph Initial As concentration 500 µg/l, adsorbent dosage 1 mg/l, contact time 8h
Effect of initial arsenic concentration 100% As(V) adsorbed 80% 60% 40% 20% 0% 0.5 2 8 hrs, IGAC 0 600 1,200 1,800 Initial As(V) concentration (mg/l) adsorbent dosage: 2 g IGAC /L
Effect of initial arsenic concentration b 100% 80% As 5+ adsorbed 60% 40% 20% 0% 0 500 1,000 1,500 IGAC dosage: Initial As 5+ concentration (mg/l) 0.1 0.4 0.8 2 8 g/l Contact time: 8 hours
Tea bag based POU system 100% 100% As(III) adsorbed 80% 60% 40% 20% 0% As(III) adsorbed 80% 60% 40% 20% 0 2 4 6 8 10 Contact time (days) 0% IGAC ICS Adsorbent (IGAC) without shaking with shaking without shaking contact time: 8 hours adsorbent dose: 8 g/l; model water:» 500 µg As(III)/L
Coffee filter based POU system 30 ml ICS or IGAC, contact time: 1 minute
Coffee filter based POU system As(V) (mg/l) 400 300 200 Influent Bangladesh standard IGAC (1st filtrate) IGAC (2nd filtrate) 100 0 0 50 100 150 200 Filtered bed volume
600 Filtration based POU system As(V) (mg/l) 500 400 300 200 100 average As(V) influent Bangladesh standard WHO standard ICS filtrate IGAC filtrate 0 0 4 8 12 16 20 24 Filtered bed volume (x100) adsorbent used: 300 ml, contact time: 21 minutes
Arsenic concentration in model water: 500 µg As/L 60% Wells exceeding 40% 20% 0% <10 >10 >50 >100 >250 >500 > 1000 Arsenic concentration in mg/l