ANALISIS HISTORICO

Resources Research Institute

Gammaa A.M. Osman, Eiman E.E.

Diab, Hajo E. ElHassan, and Izat M. Taha

Environment and Natural Resource Research Institute, National Research Center, Khartoum, Sudan

Abstract

Despite the presence of the Nile river and other surface and ground water resources, Sudan, like other arid and semi arid countries, faces water short-age problems. Storshort-age limitations, the erratic nature and distribution of rainfall, population growth, rising living standards, and accelerated urban-ization, all threaten the water supply in general and agriculture in particu-lar. This situation drives research to develop additional water resources as well as protect the existing ones. The Environment and Natural Resources Research Institute, a specialized research institute in Sudan, has been work-ing for several years on reuswork-ing wastewater and sewage sludge in agricul-ture to solve both problems of environmental pollution and water scarcity in agriculture. There have been many research projects on the use of wastewater and sludge addressing cultivation of forest trees, ornamental plants, forage crops, fruits, and vegetables through monitoring of such water and sludge and of quantity and quality of agricultural products. The accumulation effects of both wastewater and sludge on the physical, chemical, and biological characteristics of soil have also been studied. This paper presents the wastewater and sludge reuse results and prospects.

Key words: sewage sludge, wastewaer treatment, heavy metals, wastewater irrigation, Sudan

1 Introduction

Sudan is the largest country in Africa and the Middle East, and covers an area of about 250 million ha in the tropical zone at 3-22° N and 22-38° E.

One third of the total area is arable; however, only 21% of the arable land is cultivated. There are many surface and ground water resources in

Research on Wastewater Reuse in Sudan

Sudan. Rainfall provides much of the available surface water and varies significantly; the rainy season, especially in the north, is limited to 2-3 months and the rest of the year is virtually dry. Moreover, the rain is usually in isolated showers, which are highly variable in time and location.

Furthermore, Sudan contains 60% of the Nile Basin and shares 22% of the Nile water with Egypt, according to the 1959 agreement. Owing to the population growth and water demand in different sectors, there is a need for long-term planning of research to improve water management in the country.

Scientific research in Sudan addressing water management is carried out by several universities and scientific research institute. The Environmental and Natural Resources Research Institute (ENRRI) is the one of the special-ized research institutes of the National Center for Research in Sudan. ENRRI has worked for several years in many research projects concerning envi-ronment and natural resources, with wastewater reuse in agriculture as one of the main projects.

The research project reported here aims at sustainable use of treated wastewater while protecting the environment, providing economic bene-fits, and supporting the country's development, by conducting research on monitoring and reuse of treated wastewater and sludge in agriculture as a model for future use in Sudan.

2 Treated wastewater in Sudan

The first wastewater treatment plant in Sudan was established in the Elgoz area in south Khartoum in 1958, to treat about 13.5 million liters of sewage water per day from the central Khartoum area. This plant treated waste-water by the activated sludge process. In 1990, a new plant was estab-lished in the Soba area of south Khartoum with an oxidation pond system, to deal with increased volumes from the central Khartoum area and the industrial area. This plant was designed to treat about 40 million liters of mixed domestic and industrial water (Elrashid et al. 1998, 1999, Taha 2000)

3 ENRRI experience with treated wastewater

For several years, to evaluate reuse of wastewater and sludge in agricul-ture, ENRRI has implemented several wastewater monitoring and reuse experiments. These have aimed to demonstrate that treated wastewater reuse can be reliable, economically viable, socially acceptable, and envi-ronmentally safe (Diab et al. 2006, Osman et al. 2006).

Sustainable Management of Wastewater for Agriculture

4 Wastewater and sewage sludge characteristics

The physical, chemical, and biological quality parameters of treated wastewater and sewage sludge were conducted many times in parallel with reuse of these wastes in specific experiments (Tables 1 and 2). Most cases demonstrated the feasibility of reuse of wastewater and sewage sludge with some precautions.

5 Effect of wastewater and sewage sludge

During the years 1997-2007, many pot and field studies were conducted in the ENRRI nursery and in field locations in the Soba area. These studies evaluated the effects of various levels of treated wastewater and sewage sludge (fermented or non-fermented) on growth, yield, quality attributing characters, and the metal accumulation in tissues of different forestry species, forage crops, and vegetables.

Table 1 Characteristics of wastewater and sludge reported in 2002 from a wastewater treatment plant using oxidation pond system in Khartoum.

Parameter Unit Wastewater (mg L^-1) Sewage sludge

pH - - 7.35

Table 2 Characteristics of wastewater and sludge reported in 2005 from a wastewater treatment plant using oxidation pond system in Khartoum

Parameter Unit Wastewater Sewage sludge

pH - 7.3 7.58

Table 3 Maximum heavy metal concentrations (mg kg^-1) in lettuce (Lactuca sativa L.) and Jew's-mallow (Corchorus olitorius L.) as affected by treat-ed wastewater

The studies indicated that increased application rates of treated waste-water and sewage sludge (fermented or non-fermented) significantly increased the yield, vegetative growth, and quality parameters for most tested plants. There was no significant effect on metal concentrations with wastewater and sludge levels; in most studies, the uptake of metals

depended on plant species (Table 3). Metal residues were generally less than the maximum permissible levels for vegetables, with the exception of Cr in some cases; possibly due to low heavy metal concentrations in treat-ed wastewater and sludge ustreat-ed. However, the high Cr concentration was due to the tannery industry that was dominant and regularly linked with the sewerage system.