MICROBIOLOGICAL TESTS AND ASSESSMENT OF SEWAGE SLUDGE FROM WASTE WATER TREATMENT PLANTS IN CONNECTION TO ITS USAGE AS A SOIL IMPROVER
Journal Title: Българско списание за обществено здраве (Bulgarian Journal of Public Health) - Year 2017, Vol 0, Issue 1
Abstract
Motivation Large amount of sewage sludge is produced during biological waste water treatment. Most of it is with compromised sanitary microbiological parameters. In order to be used as a soil improver, the sewage sludge should meet the national legislation requirements. For this reason, methods for further sludge treatment are being developed in order to accelerate the achievement of the desired microbiological quality of the sludge and provide grounds for its use as a soil improver. Aim: The purpose of this study is to establish and compare the microbial content of sewage sludge treated with 20% fine lime and such without treatment, in order to be used in the agricultural practice. Methods: Verified internal laboratory test method is applied. In order to establish the microbiological characteristics of the sewage sludge were analyzed average samples of mature sludge from 13 wastewater treatment plants (WWTP) throughout Bulgaria. Results :The sewage sludge is tested for microbiological parameters laid down in existing regulations. The hygienic condition of the sludge is evaluated for presence of E.coli, Clostridium perfringens and microorganisms of the genus Salmonella. Additional groups as indicator microorganisms of faecal contamination - coliforms and enterococci are also tested. The total number of microorganisms in 1g sample is studied to establish how the treatment of the sludge affects the total quantity of saprophytic microflora, involved in the self-purification process. The treated sludge does not contain indicator microorganisms and has low number of saprophytic bacteria in contrast to the untreated sludge, where indicators of faecal pollution and saprophytes in larger quantities are isolated Conclusion: Despite the fact that liming has changed the agrochemical characteristics of the sewage sludge, through it the sanitary and microbiological parameters of the sludge are improved, which accelerates its use in practice as a soil improver.
Authors and Affiliations
Vesela Georgieva, Svetla Marinova, Momchil Djambazov
Keywords
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