Groundwater Quality and Protection defining strategies and setting priorities Learning Objectives To assess and identify threats and pollution hazards to groundwater quality To discuss ways of protecting groundwater from pollution. Definition of common groundwater pollution terms Term Definition sensitivity to contamination, determined by the natural Aquifer intrinsic characteristics of geological strata forming the Pollution overlying confining beds or vadose zone of the aquifer Vulnerability concerned probability that groundwater in an aquifer will become Groundwater polluted to concentrations above WHO drinking-water Pollution guidelines when a given subsurface contaminant load is generated at the land surface Hazard threat posed by hazard to human health due to Groundwater pollution of a specific groundwater supply source, or to Pollution an ecosystem, due to pollution of a specific natural aquifer discharge. Risk How do aquifers become polluted? When contaminant load (effluent discharge and/or leachate): is inadequately controlled/disposed of. exceeds natural attenuation capacity of underlying soils and strata. groundwater merits protection because it provides vital source of potable water supply Outline of Pr esenta tion 1. Rural water supply 2. Urban- and Peri-urban settlements 3. Groundwater Protection Zones Rural Water Supply Currently 53 % of Africa‘s rural population is without access to safe water (AfDB 2009) „Safe drinking water“ is predominantly from hand-dug-wells and drilled wells with hand pumps Frequent reports in literature indicate elevated nitrate levels and bacterial contamination Rural Water Supply (contd.) High levels of nitrate and Gyau-Boakye, P. et. coliforms in hand-dug wells in al. (2008) Ghana 33 % of 2200 wells in Nigeria Adalena, S. et. al. have nitrate values above 45 (2008) mg NO3/L 38 % of water from boreholes Agyekum, W.A. et al. in a district in Ghana have (2008) nitrate concentrations above 45 mg/L Contamination sources dirty water at well head recirculating into the well McDonold et. al. (2005) Contamination sources (contd.) Pollution from animal faeces Protection measures Proper well construction can significantly improve water quality Well location upstream/away from pit latrines, waste dumps and cemeteries Concrete platforms around well with proper drainage Animals must be kept away by a fence Protection measures (contd.) Proper well construction www.ualberta.ca/~xcle/img/pump.jpg www.wateraid.org/images/cm_images/pump-web.jpg Concrete platforms around the well Fencing to keep away animals http://rehydrate.org/dd/img2/su312.jpg Peri-urban settlements Present situation in Peri-urban settlements in Africa: Uncontrolled settlement Predominant use of on site-sanitation Uncontrolled waste dumping Water supply predominantly from dug wells or water ponds Extensive contamination by nitrate, nitrite, ammonia, and faecal bacteria Frequent outbrake of water-borne diseases (cholera). Contamination sources Retention of solids Infiltration of liquids Pathogens Nitrates Viruses Source: GTZ (Werner) 2005 Polluted groundwater Source: Nkhuwa 2006 Strategies to improve pollution situation in Periurban areas Connection to public water supply (piped water system) Connection to sewerage system No realistic short term solution (high investment costs) Str a tegies to impr ove pollution situa tion in Peri-urban areas (contd.) Improvement of on-site sanitation through reuse of faecal matter (dry toilets – ecosan). Dehydrating toilets Source: CSIR 2004 Str a tegies to impr ove pollution situa tion in Peri-urban areas (contd.) Improvement of on-site sanitation through use of low cost wastewater treatment. Wastewater treatment Source: BGR 2008 The Urban Environment Land-use activities commonly responsible for groundwater pollution in the Urban areas. Contamination sources to water supply points in Urban areas Contamination sources to water supply points in Urban areas Wastewater drain – Accra, Ghana Contamination sources to water supply points… (contd.) Fuel spillage from a tanker that overturned @ a petrol station in Lusaka. Non-aqueous phase liquid contamination Common grdwater contaminants and associated pollution sources Pollution source Type of contaminant Agricultural Activity nitrates; ammonium; pesticides; faecal organisms In-situ Sanitation nitrates; faecal organisms; trace synthetic hydrocarbons Gasoline Filling Stations & Garages benzene; other aromatic hydrocarbons; phenols Solid Waste Disposal ammonium; salinity; some halogenated hydro-carbons; heavy metals Dry Cleaning trichloroethylene; tetrachloroethylene Sewage Sludge Disposal nitrates; various halogenated hydrocarbons; lead; zinc Leather Tanneries chromium; various halogenated hydrocarbons; phenols Groundwater Protection Common approach worldwide: Protection of water resources by Groundwater Protection Zones (GPZ) – to be discussed in detail later General aim: To Protect drinking water resources in the groundwater contribution zone, upstream of a well/spring, from pollution. What treatment is groundwater before consumers? applied to the it is piped to Re m e d i a l measures Vulnerability of aquifers to pollution Threats to groundwater pollution are a function, among others, of: Thickness & properties of overlying soil (vadose zone) Depth to water-table. Vulnerability of aquifer to pollution (contd.) Thin vadose zone & shallow water-table provides less natural attenuation, prone to pollution. Vulnerability of aquifer to pollution (contd.) Deeper and confined aquifers have much greater natural protection by the overlying ground. Vulnerability of aquifer to pollution (contd.) Pollution Pathways by Sanitation How can groundwater pollution hazard be assessed? from the hydrogeological characteristics of the overlying material. used to produce a vulnerability index that can be mapped a variety of vulnerability assessment tools may be used e.g.: DRASTIC method How can groundwater pollution hazard be assessed? (contd.) DRASTIC D - depth to water R - net Recharge A - aquifer media S - soil media T - topography I - impact of vadose zone C - hydraulic conductivity Pollution Hazard Assessment How can groundwater pollution hazard be assessed? (contd.) When map of potl contaminant load overlain on aquifer vulnerability map, it will provide a map of groundwater pollution hazard. Groundwater protection Its General aim: To protect drinking water resources in the groundwater contribution zone upstream of the well/spring from pollution. Common approach worldwide involves: Protection of water resources by Groundwater Protection Zones (GPZ) Zone I – Zone II – Zone III – Immediate Protection Zone Inner Protection Zone Outer Protection Zone employing Groundwater protection (contd.) Zone 1 – Protects well/spring from direct contamination Well I II Zone II – Protects drinking water source against pathogenic microbiological constituents bacteria, viruses, parasites. III Groundwater Flow Direction Zone III – Protects against contamination affecting drinking water source over long distances (for chemical substances, which are non- or hardly degradable) Groundwater protection (contd.) Grdwater Protection Zones : need regulatory embedding need public awareness need Monitoring usually imply landuse restrictions to balance competing user-interests. Who should promote groundwater pollution protection? The ultimate responsibility for groundwater pollution protection lies with relevant government agency...... Thank you for your attention Exercise – Waste Management Role Play You are required to improve waste management / effluent disposal in the capital city in your country. Participants divide into stakeholders: Water/Groundwater managers; Waste Disposal companies; Industry discharging effluent; Citizen Groups; Politicians. The water managers must propose sweeping reforms to improve all aspects of waste management in the city for the purpose of protecting quality of groundwater (& surface water). The other stakeholders should raise queries about the impact of the changes on them, & make objections/suggestions to the water managers. Preparation: 20 minutes Debate: 40 minutes. EXERCISE Purpose: To share experience of groundwater quality problems. Activity: Break into groups of 4 or 5. 1 hour. Each group to Identify a common groundwater quality problem in one of your countries. Discuss the nature & scale of the problem – is it anthropogenic or natural? How is the problem being managed and who is responsible for the management? What have been the aims of the management and how successful has it been? What would you need to change to improve the situation? Report back: 15 minutes per group.