Abstract:Since 1990, more than 1.8 billion people have gained access to potable water and improved sanitation worldwide. Whilst this represents a vital step towards improving global health and well-being, accelerated population growth coupled with rapid urbanization has further strained existing water supplies. Whilst South Africa aims at spending 0.5% of its GDP on improving sanitation, additional factors such as hydrological variability and growing agricultural needs have further increased dependence on this finite resource. Increasing pressure on existing wastewater treatment plants has led to the discharge of inadequately treated effluent, reinforcing the need to improve and adopt more stringent methods for monitoring discharged effluent and surrounding water sources. This review provides an overview of the relative efficiencies of the different steps involved in wastewater treatment as well as the commonly detected microbial indicators with their associated health implications. In addition, it highlights the need to enforce more stringent measures to ensure compliance of treated effluent quality to the existing guidelines.

The physico-chemical characteristics and microbial composition of the final effluents of two municipal wastewater treatment plants in South Africa were assessed between July and September 2009. The impact of the treated final effluents on the receiving water bodies was also evaluated. The temperature across all sampling points ranged between 14 and 228C, while pH varied from 6.9 to 7.6. High levels of turbidity, chemical oxygen demand (COD), ammonia, nitrate, nitrite and orthophosphate (PO 4 ) were observed in many cases. Turbidity of the samples was in the range of 2.2-288.6 NTU. The concentrations (mg/L) of other physico-chemical parameters are as follows: COD (9.33-289); ammonia (0.000340-45.4); nitrate (0.062-539); nitrite (0.021-22.6); PO 4 (5.3-33.2). The microbial quality of the effluents discharged from the plants did not comply with the limits set by the South African guidelines with respect to pathogens such as Salmonella, Shigella, Escherichia coli, total coliform, faecal coliform, enterococci, faecal streptococci, and viral particles for effluents intended for discharge into receiving watersheds. This study revealed an undesirable impact on the physico-chemical and microbial qualities of the receiving water bodies as a result of the discharge of inadequately treated effluents from the wastewater treatment facilities. This poses a health risk to several rural communities which rely on the receiving water bodies primarily as their sources of domestic water and recreational purposes. There is therefore a need for the intervention of appropriate regulatory agencies in South Africa to ensure compliance of treatment facilities with wastewater effluent quality standards.

Modified chitosan was prepared by chemical derivatisation using caproyl and palmitoyl fatty acid chains. The performance of the materials on the removal of phosphates in aqueous solutions was evaluated through a series of batch adsorption experiments. The phosphate adsorption studies showed enhanced adsorption efficiencies for caproyl chitosan (63%) and for palmitoyl chitosan (71%) in aqueous solutions containing phosphate at a pH of 6.2. The pristine and modified chitosans showed increases in the removal efficiency at an optimal solution pH of 4. The adsorption kinetics studies performed on palmitoyl-chitosan indicated that a contact time of approximately 30 minutes is required to reach equilibrium at solution concentrations ranging from 10-20 mg/l. Co-existing anions such as nitrates and sulphates do affect the phosphate removal efficiency of modified chitosans in aqueous solutions. This study demonstrates that modified chitosans has the potential of being used as a rigid and degradable material for water treatment.

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