The Water-Waste Nexus: Sustainability Implications for Integrated Water Resources and Waste Management in Harare

Introduction

The management of waste has been reported and singled out amongst the greatest challenges affecting urban local authorities (ULAs) in developing nations. Such waste includes municipal solid waste (MSW) and wastewater (WW). The challenges are a manifestation of reported astronomical increase in the generation of both MSW and WW within urban environments in developing nations resulting from increased urbanisation due to population increases and rural to urban migration in search of better lifestyles and jobs (Cheng & Urpelainen, 2015; Cohen, 2006; UNDESA, 2018). Increased urbanisation has also brought about the sprouting or emergency of informal settlements outside the urban development master plans which have remained inaccessible to and unserved by the water resources, MSW and WW management services. The majority of MSW generated in these developing nations especially within Africa is unsustainably managed with almost or above 50% being subjected to landfilling with no energy recovery, landfill leachate treatment and landfill gas capture or flaring, whilst the remaining MSW is subjected to dumping at official dumpsites or illegally burnt or buried at source, indiscriminately dumped and strewn in undesignated areas such as vacant spaces, road sides, allays, streets, storm water drains etc. (Hoornweg & Bhada-Tata, 2012). This is so because the increased MSW generation has not been matched with corresponding municipal solid waste management (MSWM) systems developments with regards to infrastructural development (equipment and technology), skills and expertise capacity building and MSWM investments (Yadav, Karmakar, Dikshit, & Vanjari, 2016). The volumes of WW being produced far outstrips the design and commissioned capacities of the wastewater treatment plants (WWTPs) resulting in raw or partially treated WW or sewage being discharged into the environment and water bodies.

Surface run off and on carries with it leachate and other MSW materials from the official dumpsites and undesignated areas depositing them into water bodies. Leachates from the MSW dumpsites and other undesignated areas where MSW is discarded and strewn percolates into the ground polluting the groundwater. The deposition of MSW derived leachate from dumpsites and other MSW materials from the indiscriminately discarded and strewn in runoff during rainfall events together with the discharge of raw or partially treated WW have significantly contributed to the pollution and eutrophication of water bodies. MSW contributes to increased eutrophication of water bodies largely due to the high biodegradable MSW composition in the MSW generated in the developing nations reported to be in excess of 40%, which is anticipated to load nutrients into water bodies when in contact with or laden in run off. The increased urbanisation result in increased demand for portable water which entails increased water pumping power requirements and costs coupled with the need to further expand or extend the potable water supply systems. The MSW derived pollution and eutrophication of water bodies thus is not a welcome phenomenon as it will exacerbates an already strained situation from the resultant increased costs for raw water treatment to potable standards. When surface water supply systems become strained, residents resort to groundwater sources which are unfortunately being laden with leachates from dumpsites polluting the groundwater with heavy metals and other pollutants making the groundwater unfit for potable water uses. A water and waste nexus therefore exists and it is evidently clear that the unsustainable management of MSW and WW impacts heavily on water management thereby bringing in disruptions within the water and waste management nexus. The sustainable management of MSW and WW is thus anticipated to result in the sustainable management of water resources due to the corresponding reduced MSW and WW associated water pollution. The water and waste nexus thus has been negatively impacted with regards to sustainability planning in majority of urban centers within developing nations.