Ghana: An Urban Wastewater Solution – African Vetiver Grass

Posted in: Crisis Response, Global Water News, Water Contamination
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Article courtesy of AllAfrica | January 5, 2015 | AllAfrica.com | Shared as educational material

The world is witnessing a water quality crisis, mainly brought about by rapid population growth, industrialization, food production practices and poor water use strategies. As population increases, so does wastewater output. In developing countries, about 90 per cent of all wastewater is discharged untreated directly into rivers, lakes and oceans.

The impact of wastewater on the environment and human health is not only striking but frightening. A report by the United Nations Environment Programme (UNEP) and UN-HABITAT in partnership with members of UN Water indicates that two million tons of sewage, industrial and agricultural waste are discharged into the world’s waterways and at least 1.8 million children under five-years-old die as a result every year. That is, one child lost every 20 seconds due to water related diseases.

Inadequate infrastructure and lack of financial resources are largely to blame for the wastewater menaces that plague most developing countries, especially their cities. In these countries, septic tanks receive the faecal waste of most urban dwellers, while other household liquid wastes are directed into the nearest drains.

Because drainage system costs are frequently prohibitive, the majority of urban drains are open, lending themselves to misuse and sometimes serving as defecation points for households without adequate sanitation facilities. Industrial wastewater — from breweries and other sources such as the textile, mining, chemical and pharmaceutical industries — is usually discharged into these open drains or into water bodies without any pre-treatment, posing health hazards.

The quest for a cost effective technology

Managing wastewater in an efficient and sustainable way calls for a multifaceted approach. Various measures including behavioural change approaches towards combatting water pollution and the use of appropriate infrastructure, technologies and techniques will help reduce the impact of wastewater on the environment and on humankind.

The quest for an immediate approach to wastewater treatment in developing countries has spurred research within the scientific community. Among that research is a project being carried out by the United Nations University Institute for Natural Resources in Africa (UNU-INRA) in partnership with Ebonyi State University in Nigeria.

The project is assessing the potential of an African vetiver grass species, Chrysopogon nigritana, in treating industrial effluents and wastewater from domestic origins, which have been major sources of contamination. In Africa wastewater is increasingly becoming important resource for various uses including irrigation in urban and peri-urban agriculture. This wastewater is often high in toxic heavy metals including arsenic, cadmium and manganese as well as components of nutrient pollution such as phosphates and nitrates.

The general findings of this vetiver project reveal that Chrysopogon nigritana can reduce these contaminants in industrial effluents and domestic wastewater. For example, in one case, samples were taken of leachate from a dumpsite and treated with Chrysopogon nigritana for seven days. Laboratory analysis of the chemical properties of the treated leachate indicated that phosphate, which was at a pre-treatment level of 92.9, was reduced to 19.71 mgl-1, while Chemical Oxygen Demand (COD) dropped from 151.78 to 50.57 mgl-1. These levels are far below the United States Environmental Protection Agency’s (USEPA) permissible limits of 50 and 75 mg l-1 for each of these respective chemical properties in water.

Similarly, laboratory results showed that arsenic and cadmium properties, which were both initially at pre-treatment levels of 0.2mg l-1, were completely removed from sample effluents taken from a fertilizer company after a six-day vetiver grass treatment. The absence of these chemical properties after treating the effluents with the vetiver grass is very satisfactory because the World Health Organisation /Food and Agriculture Organisation’s (WHO/FAO) acceptable levels for arsenic and cadmium in water are 0.10mg l-1and 0.005mg l-1 respectively.

Additionally, analysis of a sample slaughterhouse wastewater treated for seven days by the vetiver showed about 88 percent reduction in manganese (from 1.03 mg l-1 to 0.12 mg l-1) — a reduction well below the WHO/FAO’s safety standard of 0.20 mg l-1 for manganese in water.

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