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USE OF DOMESTIC WASTE WATER FOR IRRIGATION OF VEGETABLE CROPS: THE HEALTH IMPLICATIONS

CHAPTER ONE

1.0 INTRODUCTION

The population of Nigeria is always on the increase, with the World Bank estimating the population of Nigeria to hit over a 300 million in the year 2035, the gap between the supply and demand for water is widening and is reaching such alarming levels that in some parts of the world it is posing a threat to human existence. Since 1950 the world population has doubled while water consumption has increased six- fold. By 2025, it is expected that 3.4 billion people will be living in countries defined as water-scarce. Scientists around the globe are working on new ways of conserving water. It is an opportune time to refocus on one of the ways to recycle water-through the use of wastewater for irrigation and other purposes.

Wastewater refers to water whose quality might pose a threat to sustainable agriculture and/or human health, but which can be used safely for irrigation provided certain precautions are taken. It describes water that has been polluted as a result of mixing with Waste or agricultural drainage (Cornish et al 1999). Pierce and Turner (1990) defined wastewater as water that possesses certain characteristics which have the potential to cause problems when it is used for an intended purpose. In this work, it is assumed that wastewater may be a combination of some or all of the following:

Storm water and other runoff.

Domestic effluent consisting of black water (excreta, urine and associated sludge) and grey water (kitchen and bathroom wastewater).

Wastewater from farm houses and fish ponds.

Reserved wastewater from residences.

Water from commercial establishments and institutions, e.g. hospitals.

The main sources of wastewater are domestic and industrial. As a general rule 80-85% of water used is wasted (Spore 2002).

Plate 1: Vegetables farm irrigated with domestic wastewater Ghana

Source: PEASEY A (2000)

Statement of the Problem

Wastewater use in crop production is not without some risks. The main risk associated with wastewater irrigation is infection with intestinal helminthes. Also, depending on the source of the wastewater it might contain chemical pollutants and heavy metals that can accumulate in the soil and crops thereby posing a threat to human health. However, a major drive towards wastewater use is the fact that it contains high levels of nutrients, reducing the need for and cost of fertilizers. Consequently, many farmers using wastewater are better able to support themselves and their families and often create extra employment (Spore 2002). Furthermore, the continuous demand for certain crops especially vegetables has increased the need to cultivate these crops all year round. This in effect leads to the dependence on wastewater during the dry seasons or during periods of drought. Also, due to the light water requirement of some crops, the use of wastewater to augment the freshwater, if any, becomes inevitable. In many areas, the few freshwater supply stations (boreholes) are owned by individuals, and the water is sold to others who cannot afford to set up one. In such a situation, the resource poor farmers are forced to resort to a cheaper alternative – wastewater. However, unregulated use of wastewater poses some risks to human health and the environment. Because of these risks, the prevailing scientific approach to wastewater irrigation advocates treatment before use. But the reality is that many developing countries lack the resources to build and maintain treatment facilities.

Objectives of the Study

1.   To evaluate the use of domestic waste water for irrigation of vegetable crops.

2.   To evaluate the health implications of domestic waste water for irrigation of vegetable crops.

Significance of the Study

This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.

Scope of the Study

This study is on the use of domestic waste water for irrigation of vegetable crops was conducted in Accra and Kumasi in Ghana.

Limitations of the study

Financial constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).

Time constraint: The researcher will simultaneously engage in this study with other academic work. This consequently will cut down on the time devoted for the research work.

Definition of Terms

Waste Water: Wastewater is any water that has been contaminated by human use. Wastewater is "used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff or stormwater, and any sewer inflow or sewer infiltration".

Irrigation: Irrigation is the artificial process of applying controlled amounts of water to land to assist in production of crops. Irrigation helps to grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of less than average rainfall.

Vegetable Farming: Vegetable farming is the growing of vegetables for human consumption. The practice probably started in several parts of the world over ten thousand years ago, with families growing vegetables for their own consumption or to trade locally.