Presentation on theme: "Groundwater Quality and Protection for Sanitation and Hygiene defining strategies and setting priorities."— Presentation transcript:
Groundwater Quality and Protection for Sanitation and Hygiene defining strategies and setting priorities
Groundwater Quality What does groundwater quality mean to you? ?
Learning Objectives To assess and identify threats and pollution hazards to groundwater quality To discuss ways of protecting groundwater from pollution.
How does Aquifer Pollution occur? Waste disposal and contaminant load is uncontrolled Waste disposal and contaminant load is uncontrolled It exceeds attenuation capacity of the ground It exceeds attenuation capacity of the ground Soil in the vadose actively attenuates many pollutants esp. domestic wastewater, and increases the time available for contaminant elimination processes Soil in the vadose actively attenuates many pollutants esp. domestic wastewater, and increases the time available for contaminant elimination processes Groundwater pollution threat is primarily to shallow aquifers Groundwater pollution threat is primarily to shallow aquifers Deep and confined aquifers can become polluted in highly fractured media and when pollution persists over a long time. Deep and confined aquifers can become polluted in highly fractured media and when pollution persists over a long time. Sharply-focused pollution control measures can produce major benefits for relatively modest cost. Sharply-focused pollution control measures can produce major benefits for relatively modest cost.
Assessment of Pollution Groundwater pollution hazard assessment is needed to appreciate the actions required to protect groundwater quality; it should be an essential component of environmental best ‑ practice Groundwater pollution hazard assessment is needed to appreciate the actions required to protect groundwater quality; it should be an essential component of environmental best ‑ practice Groundwater pollution hazard is the interaction between the aquifer pollution vulnerability and the contaminant load Groundwater pollution hazard is the interaction between the aquifer pollution vulnerability and the contaminant load Aquifer vulnerability is essentially fixed by the natural hydrogeological setting but contaminant load varies Aquifer vulnerability is essentially fixed by the natural hydrogeological setting but contaminant load varies Aquifer pollution vulnerability can be assessed from the hydrogeological characteristics of the overlying material which can be mapped (Eg. DRASTIC) Aquifer pollution vulnerability can be assessed from the hydrogeological characteristics of the overlying material which can be mapped (Eg. DRASTIC) Potential contaminant load can also be mapped and overlaid on the aquifer vulnerability map => groundwater pollution hazard. Potential contaminant load can also be mapped and overlaid on the aquifer vulnerability map => groundwater pollution hazard.
Definition of common groundwater pollution terms TermDefinition Aquifer Pollution Vulnerability sensitivity to contamination, determined by the natural intrinsic characteristics of the unsaturated or vadose zone overlying the aquifer concerned Groundwater Pollution Hazard probability that groundwater in an aquifer will become polluted to concentrations above WHO drinking-water guidelines when a given subsurface contaminant load is generated at the land surface Groundwater Pollution Risk threat posed by pollution of a specific groundwater supply source to human health or to an ecosystem due to natural aquifer (polluted) discharge.
Vulnerability of aquifer to pollution Thin vadose zone & shallow water-table provides less natural attenuation prone to pollution.
Vulnerability of aquifer to pollution Deeper and confined aquifers have much greater natural protection by the overlying ground.
Pollution Pathways by Sanitation Vulnerability of water well to pollution
Aquifer Vulnerability Mapping G Groundwater hydraulic confinement O Overlying strata D Depth to groundwater => Vulnerability Index
Groundwater Vulnerability Map DRASTIC D-depth to water R-net recharge A-aquifer media S-soil media T-topography I-impact of vadose zone C-hydraulic conductivity
Common grdwater contaminants and associated pollution sources Pollution sourceType of contaminant Agricultural Activitynitrates; ammonium; pesticides; faecal organisms In-situ Sanitationnitrates; 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 Cleaningtrichloroethylene; tetrachloroethylene Sewage Sludge Disposal nitrates; various halogenated hydrocarbons; lead; zinc Leather Tannerieschromium; various halogenated hydrocarbons; phenols MiningAcidity, iron, heavy metals, sulphate
Rural Water Supply Gyau-Boakye, P. et. al. (2008) High levels of nitrate and coliforms in hand-dug wells in Ghana Adalena, S. et. al. (2008)33 % of 2200 wells in Nigeria with nitrate values above 45 mg NO 3 /L Agyekum, W.A. et al. (2008) 38 % of water from boreholes in one district in Ghana nitrate concentrations above 45 mg/L
Contamination sources dirty water at well head recirculating into the well McDonold et. al. (2005)
Protection measures Proper well construction can significantly improve water quality Well location upstream/away from pit latrines, waste dumps and cemeteries around well with proper drainage Concrete platforms around well with proper drainage Animals must be kept away by a Animals must be kept away by a fence
Protection measures (contd.) Concrete platforms around the well Proper well construction Fencing to keep away animals
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 outbreaks of water-borne diseases (cholera).
23 Choice of location of Pit latrines in high- density settlements Systems of Human Waste Disposal Toilet Well
Strategies to improve pollution situation in peri-urban areas Connection to public water supply (piped water system) Connection to sewerage system These are very expensive options Alternative systems: Ecosan Toilets / Constructed wetlands
Improvement of on-site sanitation through reuse of faecal matter (dry toilets – ecosan). Dehydrating toilets Source: CSIR 2004 Strategies to improve pollution situation in Peri-urban areas (contd.)
Source: BGR 2008 Wastewater treatment Improvement of on-site sanitation through use of low cost wastewater treatment. Strategies to improve pollution situation in Peri-urban areas (contd.)
Contamination sources to water supply points in Urban areas What is the impact of such waste on water....?
Contamination sources to water supply points… (contd.) Fuel spillage from a tanker that overturned at a petrol station in Lusaka. Non-aqueous phase liquid contamination
Pollution Risk to Human Health
High nitrates and bacterial contamination are common. Poor sanitation and informal sewage disposals are the major contributors to groundwater quality degradation. Pollution of underlying groundwater sources mainly from pit-latrines and broken septic tanks has reached critical levels, leading to typhoid outbreaks. Increasing contamination from industrial, agricultural and mining activities
Delineation of Groundwater Protection Area (GPA) GPAs also need: - regulatory embedding - public awareness - monitoring designed to provide special vigilance for groundwater destined for public supply simple powerful concept readily understood by planners:
Groundwater protection (contd.) Zone II – Protects drinking water source against pathogenic microbiological constituents bacteria, viruses, parasites. Well I II III Groundwater Flow Direction Zone 1 – Protects well/spring from direct contamination Zone III – Protects against contamination affecting drinking water source over long distances (for chemical substances, which are non- or hardly degradable)
Groundwater protection (contd.) Groundwater Protection Zones : need regulatory embedding need public awareness need hydrogeological data and monitoring usually imply landuse restrictions to balance competing user-interests.
How to protect against contamination? Separation – keep waste materials and groundwater far apart Separation – keep waste materials and groundwater far apart Containment – secure waste in impermeable ponds / land fill facilities Containment – secure waste in impermeable ponds / land fill facilities Waste management Waste management – sorting & separation – waste recycling / reuse – treatment of toxic waste Remediation – treat polluted aquifers – better to prevent than to treat. Remediation – treat polluted aquifers – better to prevent than to treat. Well head delineation and protection Well head delineation and protection
How to protect against contamination? Well field protection Well field protection Well spacing, pumping restriction Well spacing, pumping restriction Land use planning/regulation Land use planning/regulation Agrochemical (fertilizer/pesticide) use regulations Agrochemical (fertilizer/pesticide) use regulations Proper solid waste disposal facilities Proper solid waste disposal facilities Proper sanitation and waste water treatment facilities Proper sanitation and waste water treatment facilities Polluter-pay-principle or economic incentives Polluter-pay-principle or economic incentives Monitoring, early warning, trend analysis Monitoring, early warning, trend analysis Public awareness raising Public awareness raising
Maintaining quality groundwater supply is key to ensuring good health for all.Maintaining quality groundwater supply is key to ensuring good health for all. The level of protection in the catchment strongly influences the quality of the well water.The level of protection in the catchment strongly influences the quality of the well water. Sanitation must not be delinked from Groundwater Protection.Sanitation must not be delinked from Groundwater Protection. There is need for new sanitation and water protection initiatives inThere is need for new sanitation and water protection initiatives in Africa’s urban centers.
Overall Groundwater Remediation Strategy Restriction on GW use Development of alternative (water supply) sources Dilution with clean water Remediation/clean-up technologies Groundwater Remediation Technology Containment Ex-situ treatment In-situ treatment Natural clean-up/attenuation Groundwater Purification Aeration Filtration Mixing/dilution Desalinization Adsorption/ion exchange Chemical precipitation
Thank you for your attention
Exercise – 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.
Group Activity. Characterisation of groundwater systems Purpose: To appreciate the link between understanding groundwater systems and strategies for management Duration: 60 Minutes Scenario : 2 groups: City managers and NGO’s / User communities. The city wants to establish a solid waste disposal site on top of an important aquifer that is widely used for domestic water supply. NGO’s / Users oppose this proposal, saying that aquifer pollution is likely to occur. Activity – Role Play: City defends its position with reference to specific aquifer and hydrological characteristics, explaining why the plan is safe, and the groundwater management activities to be introduced. NGO’s / Users question the plan, referring to aquifer vulnerability and pollution remediation issues etc. and querying the aquifer management proposals.
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.