Understanding the use and disposal of greywater in the non-sewered areas of South Africa

Abstract

There is currently a strong drive from the South African government to attain adequate water and sanitation coverage throughout the country as a basic level of service. To meet this requirement the majority of authorities in urban and rural areas are implementing on-site dry latrines (VIPs or similar) and 25 litres of potable water per capita per day (lied) within a 200m eartage distance. The connection of low-income settlements to municipal water sources has subsequently occurred on a massive scale, frequently without giving adequate attention to greywater management in those areas that are non-sewered. Recent estimates show that there are approximately 20 million people in South Africa (SA) without access to on-site waterborne sanitation (Statistics South Africa, 2005). In the absence of suitable conveyance systems, greywater is generally disposed of onto the ground outside the dwellings and the resulting total pollution load, particularly from densely populated settlements, has the potential to create a host of environmental and health impacts. It is likely that the problems related to the disposal and management of greywater will increase as basic water and sanitation services are attained and improved, and solutions are therefore required to circumvent this. This thesis describes the results of a two-year investigation into the use and disposal of greywater in the non-sewered areas of SA. The main aim of the research was to quantify the greywater problem and develop options for the management thereof, both in terms of reducing health and environmental risks by eliminating inappropriate disposal of greywater, as well as possibly providing benefits to some communities through controlled use. Greywater is deï¬ ned as the wastewater that is produced from household processes (e.g. washing dishes, laundry and bathing) without input from toilets. Non-sewered areas are deï¬ ned as those areas without on-site waterborne sanitation. On-site surveys of selected communities in six of the nine provinces of SA (39 sites in total) were conducted through the use of standardised questionnaires to assess current greywater management and recycling activities. The total volume of greywater currently being generated in the non-sewered areas of South Africa has been estimated by applying an average factor of 75% to the amount of water consumed per household and multiplying this with the number of non-sewered households in each province (using modiï¬ ed Census 2001 ï¬ gures). It is estimated that a total volume of just over 490,0O0m3 per day of grey-water is generated in non-sewered areas on a daily basis in SA. This amounts to approximately 180 million m3 per year - equivalent in volume to a medium sized dam such as Voelvlei near Cape Town, or approximately 50% of the current annual water demand of this city. This illustrates the relatively limited potential for the use of greywater from non-sewered areas as an alternative water resource at a country-wide scale, and suggests that the main beneï¬ ts from greywater use in these areas will be from irrigation at household level to supplement nutrition requirements. On the other hand, these ï¬ gures highlight the fact that greywater disposal in non-sewered areas is likely to result in signiï¬ cant health and environmental impacts, particularly in dense urban environments where large volumes of greywater are generated in relatively small areas. Limited water quality sampling of typical greywater and source water was undertaken during the surveys to try and get a general understanding of the overall quality of the greywater emanating from non-sewered areas, particularly in respect of its nutrient loading and oxygen demand. The results suggested that greywater is generally unï¬ t for use except under controlled conditions. In particular, not enough is known at present about the health challenges that may be faced by the use of greywater for the irrigation of food crops, and the management of any recycling practice is therefore crucial. Unrestricted use of greywater without education on the risks involved and supervision of the practice to ensure adherence to safety precautions is likely to increase the disease burden on those who can least afford it. The determination of typical volumes of greywater generated per hectare for non-sewered settlements and the likely impact of changes in service levels with respect to water supply have been calculated by using average water consumption data determined from on-site surveys and updated settlement data from Census 2001. A model has been developed in which greywater management options for non-sewered areas are determined by way of a series of rule-based flow diagrams which raise relevant questions for each of the criteria in order to assess various alternatives for greywater management and disposal. Two main outputs have therefore resulted from the research; one at a strategic level and the other at an implementation level. Recommendations have been made to assist government policy makers in the development of strategies for the management of greywater, and greywater management options have been identiï¬ ed so that communities and municipal planners can implement the solutions required to reduce any negative impacts.