Microbial Environmental Risks Associated Sewage Sludge Disposal

Sewage sludge disposal is a worldwide problem and a wide variety of disposal routes have been adopted as directed by local condition. Disposal of sludge to land can be beneficial because it contains plant nutrient (N and P) and organic matter. Sludge and sewage are a public health threat, which has been linked to respiratory problems and death. Sludge disposal is a major operational cost in the treatment of waste water and in the water industry tends to dispose of sludge at minimum cost consistent with acceptable environmental impact and with flexibility and security. All sludge in world contains heavy metals like arsenic, cadmium, chromium, copper, lead mercury, molybdenum, nickel, selenium, and zinc. Sewage sludge, by its very nature contains a wide variety of pathogens including bacteria, viruses, fungi and eggs of parasites. Pathogens may also enter the sewerage system from farm drainage, domestic animals, and the rodent population of the sewer sand surface water. Directly or indirectly in 1 year 300,000 tons of sewage sludge (dry weight bases) generated and disposed currently, about 17% of the MSW (municipal solid wastes) is recycled; the other 83% is disposed of in landfills or incinerated. To avoid environmental problems it is necessary to recycle the sludge before disposal.