By Ogwal Paul, Re!gnite Africa Youth Leader
The growth of slums in urban areas in developing countries causes sanitation challenges for the urban authorities. The main challenges are related to the collection as well as treatment of excreta, solid waste and wastewater for the protection of human health and the environment. Fecal sludge management has traditionally been considered the main issue concerning improvement of sanitary conditions in urban slums because excreta are the source of many pathogens. In contrast, the grey water streams that account for the largest volume of wastewater generated in non-sewered urban slums have so far not been prioritized in sanitation provisions.
Greywater is the wastewater produced from baths, showers, clothes washers, and lavatory sinks; this is about 50-80% of the household water consumption which goes directly down the drain. The wastewater flushed by toilets, kitchen sink, and dishwasher drains, is called black water.
A recent study was carried out in Bwaise III slum in Kampala city (Uganda) during the period of January–April 2010 and May–August 2012. It is a typical slum area located in a reclaimed wetland (32_ 340E and 0_ 210N) and is drained by two major open storm water channels into which tertiary drains discharge grey water and storm water. The area experiences two dry season periods from January to March, and from June to August. Even though there is an extensive coverage of piped water supply infrastructure in this area by NWSC, residents in the area do not necessarily access clean potable water because they cannot afford to pay. They resort to shallow ground water sources in the form of springs that are contaminated. The area is not sewered, and the majority of residents use on-site sanitation in the form of elevated pit latrines.There is no wastewater management system in place, therefore grey water is not properly managed.
The quality and quantity of grey water are influenced by the high population density, unplanned low-cost housing units with limited accessibility, income level, cultural norms and type of cleaning detergents used.Grey water discharge results in both short-term and long-term effects on the environment and human health. Soil and ground water pollution and damage to crops are caused by high concentrations of chemicals such as boron, sodium or surfactants, some of which may not be biodegradable.
Also, pathogenic microorganisms in grey water may cause diseases that result in either morbidity or mortality depending on the severity and duration of the exposure. These originate from households with children below 3 years because of contamination from bathing children and washing diapers.
In addition, nutrients in grey water may cause eutrophication whose occurrence depends on the self-purification capacity of the receiving environment. In particular, sodium tripolyphosphate is an ingredient of many detergents whose use has been associated with eutrophication.
Furthermore, accumulation of heavy metals and micro-pollutants in the environment may cause toxicity through the food chain, distort the ecological balance and negatively affect humans and animals after long exposure time or after bioaccumulation and biomagnification.
These negative effects from grey water are likely to be more severe in slums where sanitation is inadequate.
In many situations greywater used as an alternative water resource requires no treatment except for filtration. However, there are commercial greywater systems that do filter, and chlorinate greywater to kill off any potential harmful microbes, although this treatment with chemicals will kill off the many beneficial soil microbes, and as well can be harmful to many plants.
Construction of tertiary drains in the area where they are nonexistent, tertiary drains convey grey water from some households to storm water drains. Households located in places where there are no tertiary drains dispose grey water in the nearby open spaces.
Educate the masses who live in the urban slum areas about the dangers of grey water if not properly disposed off. This can be through campaigns and village gatherings.
The use of Greywater is a perfect solution for those concerned about green construction and sustainable development. Grey water use can also greatly extend the useful life and capacity of septic systems. For municipal treatment systems, decreased wastewater flow means higher treatment effectiveness and lower costs.