Escherichia coli die-off in swine wastewater lagoons

Then, Yin Ping (2007) Escherichia coli die-off in swine wastewater lagoons. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

In Malaysia, pig farming grew rapidly due to high demand. It is one of the most polluting livestock industries in Sarawak resulting in water and air pollution. Escherichia coli (E. coli) is used as an indicator for water quality and for possible presence of pathogenic microorganisms in water. This study is done to determine the biotic and abiotic effect on E. coli survival, the predominant factor in E. coli die-off, comparing survival in laboratory and field studies, and to evaluate wastewater lagoons efficiency. Wastewater samples for the laboratory studies were collected from wastewater lagoons of a farm in Gedon0 t was observed that E. coli population increased and maintained at high concentration in sterile wastewater compared to the non-sterile wastewater under the same condition in the laboratory study. This is possibly due to biotic factor as protozoa number was found to increase up to 8 10glO unitlmL as E. coli population dropped. Results showed that E. coli removal was enhanced by lethal pH - with pH level of more than 9 in the laboratory study. The study of E. coli survival was carried out in the laboratory and also in the field. The die-off rates ranged from 0.144 d· l to 2.835 d· l in laboratory study. Under field investigation (field batch study), the die-off rates ranged from 0.172 d· l to 1. 767 d· l . In both laboratory and field batch studies, E. coli decay rates in the wastewater from Lagoon 2 (L2) and Lagoon 3 (L3) were found to be much higher than in primary lagoons, Lagoon lA (LIA) and Lagoon IB (LIB). In both studies, it was found that there was no significant difference between die-off rates in LIA and LIB wastewater. In the field experiment, the two 7 -day field studies in September and October 2005 showed that E. coli concentrations dropped 2 10glO units after wastewater flowing through the lagoons. In addition, the lagoon system in the farm studied resulted in E. coli reduction with highest percent reduction occurred in L2 (74.9%). Correlation analysis showed that E. coli die-off rates were highly and significantly correlated with DO and pH levels.

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