Impacts of Climate on Wastewater Management Discussion Brief No 5 October 2014
Impacts of Climate on Wastewater Management The sewer is the conscience of the city Les Miserables, Victor Hugo The sewer is the conscience of the city Les Miserables, Victor Hugo Wastewater is water that has through use interacted with the human environment in such a way that it is no longer considered fit for potable use. It can include municipal sewage effluent, industrial effluent, and urban and agricultural runoff. There is also the implication that if it is consumed, without treatment, that it could be harmful to human health. Wastewater management therefore aims to minimise, control, and/or eliminate the risk to public and environmental health. Within the paradigm Integrated Water Resources Management (IWRM), wastewater management also seeks to maximise opportunities for wastewater harvesting and reuse (Keremane and McKay, 2006; Chananet al., 2010), as well as for energy and nutrient recovery from wastewater (Rulkens, 2008; Luostarinenet al., 2008). Wastewater management actions and interventions may be through: The collection, transportation and treatment infrastructure; The operation and maintenance of infrastructure; and The governing and regulatory institutional framework. A changing climate impacts wastewater management through changes in temperature, precipitation patterns, sea level rise, and storm-related damages (IPCC, 2007; McSweeneyet al., 2008). The impacts also depend on what wastewater management systems are implemented: stormwater drainage, centralised sewerage systems, or decentralised sewerage systems. Other non-climate factors, such as spatial concentration of populations, infrastructure, and economic assets, particularly in urban coastal zones, also weigh into determining the societal impact of climate change, and can expose communities to a high level of hazard and damage potential. Overall, the lack of service provision with respect to sewerage systems contributes to increased levels of vulnerability to climate change impacts. Climate-related impacts Anticipated Temperature Effects on wastewater management impacts treatment processes. Increases in ambient temperature, as well as in the number of warm and extremely hot days, will lead to warmer air, soil and water temperatures. Such increases may lead to increases in biological activity, affecting corrosion rates in water supply and wastewater pipelines. Corrosion of buried pipelines could lead to increases in pollution of groundwater sources, an important source of supply in many Caribbean states. For wastewater treatment works it has been suggested that higher temperature improves treatment efficiency due to the heat dependency of biological treatment processes Other evidence indicates that the variation in temperature can adversely affect the biological processes: warmer water temperatures lead to lower levels of dissolved oxygen, which impair biological processes, negatively affect aquatic ecology and result in poorer water quality in rivers, streams, and the marine environment. The effect of increased temperatures on greenhouse gases (GHG) emanating from wastewaters is not fully understood as yet. Firstly, centralised wastewater treatment works require energy, and increased biological activity will result in greater energy demands. Secondly, increased biological activity associated with bio-gas from soak-aways, septic tanks, and other domestic treatment systems release more methane to atmosphere, thus contributing to a positive feedback loop and further intensifying atmospheric GHG concentrations. So overall there could be a negative effect unless emissions are off-set through the capture and use of gas emissions as a source of biofuel energy. This technology exists and has been implemented (Rulkens, 2008; Luostarinenet al., 2008). With respect to Rainfall Patterns, it is likely that there will be an increase in the number of consecutive dry days, and possible lower overall rainfall (IPCC, 2007; McSweeneyet al., 2008). Dry spells will result in a loss of soil moisture 1
which induces shrinkage movement in soils, stressing pipe joints. Together with corrosion of pipe materials, this could result in increased leakage. Contamination of ground and surface waters would pose a public health concern, and coupled with higher temperatures, conditions will become more favourable for disease carriers (i.e. mosquitos) and the spread of water-related diseases such as dengue and chikungunya. It has also been suggested that climate change will lead to an overall decrease in the availability of water. To offset this one measure would be to treat and reuse wastewater (including stormwater run-off). This would require a change not only in policies and regulations, but also of public attitudes to the use of reclaimed water, whether for potable or non-potable purposes. Many of the urban areas in the Caribbean are located in low-lying coastal areas with some 40% of the population living within 2 km of the coast (Reference needed?). Given that the majority of urban areas are not serviced by a centralised sewerage system and therefore rely on other means of disposal, the impact of Sea-level Rise on these wastewater systems may be particularly severe. Sea-level Rise would cause a rise in groundwater levels, limiting the effectiveness of systems to soak away effluent and restrict biological activity. This in turn will lead to elevated levels of beach and marine pollution; contribute to eutrophication of bathing waters, and create marine dead zones making the areas less attractive to tourists and residents alike. Storm-related effects include surge damage, wind damage, and flooding. All three pose a direct threat to coastal wastewater infrastructure, which is typically located in low-lying areas and near the coast. Overwhelmed wastewater treatment plants result in raw sewage spills, as happens in Georgetown, Guyana for example. The same storm related damages impact on power transmission, which in turn affect wastewater systems. Wastewater treatment works are energyintensive operations and must have a reliable energy supply to work, without which untreated sewage is released into the environment. Wastewater management also includes Stormwater. Changes in climate are expected to increase climate variability with likely more intense rainfall events. The frequency of occurrence flood events will have to be revisited. For example, a 1- in-50-year event may become a 1-in-20-year event under climate change projections, which will place greater demands on drainage infrastructure. Storm events will also give rise to increased erosion, soil loss, and landslides. Much of the pollution and eroded soil will end up in the coastal environment. Key issues The key issues may be summarised as: Current wastewater management systems do not provide an adequate level of service that maintains and protects ecosystem services and the environment and are likely to be less effective in the future; There is likely to be an increase in GHG emissions associated with wastewater treatment; There are likely additional environmental impacts associated with water quality deterioration of freshwater resources, both surface and groundwater, which will impact on public supplies and public health; There is likely to be deterioration of the coastal marine environment, thus failure to provide adequate wastewater management will have medium- to long-term economic consequences; Decreases in freshwater availability will increase demand for alternative potable supply sources, particularly reclaimed and treated wastewater; The opportunities for energy and nutrient recovery from wastewater treatment works are being neglected. Nutrient recovery and the use of by-products could make a positive contribution to food security; A greater understanding of the impacts of climate change on wastewater treatment systems and on the management of those systems is required if the region is going to be in a position to adapt. Response The following responses are suggested: 2
Wastewater management must be better integrated with the provision of freshwater services, and assigned the same level of priority within an IWRM framework; Policies, standards, and regulations, as well as economic incentives, must be developed and implemented to address and actively promote wastewater reuse, and encourage energy and nutrient recovery from wastewater; Capacity building is required to improve adaptation to climate change in wastewater management in the Caribbean. This will require the establishment of programmes that carry out research, develop technology, and provide training to professionals in the sector; Potential financing opportunities such as through the Clean Development Mechanism (CDM) established under the Kyoto Protocol should be explored; A greater role for the Private Sector in the provision of wastewater services should be considered, but only with appropriate levels of regulatory oversight. References Chanan A., Vigneswaran S. and Kandasamy J. (2010): Valuing stormwater, rainwater and wastewater in the soft path for water management: Australian case studies. Water Science and Technology.Vol. 62.(No. 12).Pp 2854-2861.IWA Publishing. Intergovernmental Panel on Climate Change (IPCC) (2007): IPCC Fourth Assessment Report: Climate Change 2007. Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge. Keremane G. B. and McKay J. (2006): Successful wastewater reuse schemes and sustainable development: a case study in Adelaide. Water and Environment Journal.Vol. 21. Pp 83-91. Published by the Chartered Institution for Water and Environmental Management. McSweeney C., New M. and Lizcano G. (2008): UNDP Climate Change Country Profiles: Barbados. Research funded by the National Communications Support Programme (NCSP) and the UK Department for International Development (DfID). Luostarinen S., Luuste S. and Sillanpää (2008): Increased biogas production at wastewater treatment plants through codigestion of sewage sludge with grease trap sludge from a meat processing plant. Bioresource Technology. Vol. 100, (No. 1), p. 79-85. Elsevier Publishing. Rulkens W. (2008): Sewage Sludge as a Biomass Resource for the Production of Energy: Overview and Assessment of Various Options. Bioresource Technology. Vol. 22, (No. 6), p. 9-15. Elsevier Publishing. 3
Prepared by The University of the West Indies Centre for Resource Management and Environmental Studies, Barbados with the assistance of Columbia University International Research Institute for Climate and Society.Financial assistance by United States Higher Education for Development in collaboration with USAID. 4