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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 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 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. 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 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 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.
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 DDepth 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
Groundwater Pollution Hazard Map Pollution Hazard Assessment Map of potential contaminant load overlain on aquifer vulnerability map => groundwater pollution hazard map
Rural Water Supply • Currently 53 % ofAfrica‘srural populationwithoutaccess to safe water (AfDB 2009) • „Safe drinking water“predominantly from hand-dug-wells and drilledwellswithhandpumps • Frequentreports in literatureaboutelevatednitrate levels and bacterial contamination:
McDonold et. al. (2005) Contamination sources dirty water at well head recirculating into the well
Protection measures • Proper well construction can significantly improve water quality • Well location upstream/away from pit latrines, waste dumps and cemeteries • Concrete platformsaround well with proper drainage • Animals must be kept away by a fence
Protection measures (contd.) www.ualberta.ca/~xcle/img/pump.jpg Proper well construction 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 outbreaks of water-borne diseases (cholera).
Contamination sources Retention of solids Infiltration of liquids Pathogens Polluted groundwater Nitrates Viruses Source: Nkhuwa 2006 Source: GTZ (Werner) 2005
Systems of Human Waste Disposal Toilet Choice of location of Pit latrines in high-density settlements 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
Dehydrating toilets Source: CSIR 2004 Strategies to improve pollution situation in Peri-urban areas (contd.) • Improvement of on-site sanitation through reuse of faecal matter (dry toilets – ecosan).
Wastewater treatment Source: BGR 2008 Strategies to improve pollution situation in Peri-urban areas (contd.) • Improvement of on-site sanitation through use of low cost wastewater treatment.
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
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 miningactivities
Delineation of Groundwater Protection Area (GPA) simple powerful concept readily understood by planners: designed to provide special vigilance for groundwater destined for public supply GPAs also need: - regulatory embedding - public awareness - monitoring
Groundwater protection (contd.) Zone 1 –Protects well/spring from direct contamination Zone II – Protects drinking water source against pathogenic microbiological constituents bacteria, viruses, parasites. Groundwater Flow Direction II III I Well 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 • Containment– secure waste in impermeable ponds / land fill facilities • Waste management • sorting & separation • waste recycling / reuse • treatment of toxic waste • Remediation– treat polluted aquifers – better to prevent than to treat. • Well head delineation and protection
How to protect against contamination? Well field protection Well spacing, pumping restriction Land use planning/regulation Agrochemical (fertilizer/pesticide) use regulations Proper solid waste disposal facilities Proper sanitation and waste water treatment facilities Polluter-pay-principle or economic incentives Monitoring, early warning, trend analysis Public awareness raising
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. • Sanitation must not be delinked from Groundwater Protection. • There 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
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.