Micro and macro-organisms removal by a system of waste stabilization ponds

Waste stabilization pond system at Lahore, Pakistan, consisting of one anaerobic, two facultative and two maturation ponds was studied for eighteen months [December 1984 to June 1986] to study pond performances in terms of indicator organisms, pathogens and parasites removals. In all, four phases were investigated, the ponds were able to remove significant amount of total Coliforms, E. Coliforms and F. Streptococci; substantial amount of Salmonella, Shigella and Pseudomonas species; and completely E. histolytica, Ascaris and Hook-worms. The results obtained were in close agreement with Marais model of bacteria removal in waste stabilization ponds. The effluent so obtained can be safely utilized for irrigation, especially for crops which are not eaten raw

Microbiology of waste stabilization ponds in semi-arid regions

Investigations on some microbiological factors were carried out on two pond series system for three years [1979-81] treating domestic wastewater and operating at a loading of 300 lbs BOD/acre per day at a depth of 1.2 m. The study indicated satisfactory working of the ponds for monsoon [rainy], winter and spring seasons showing a removal of 58 to 72% BOD. Conditions worsened during hot summer month [May to mid July] when due to algal blooms [Oscillatoria] the pond efficiencies were restricted to 50%. The ponds also emitted odour during this period. Maximum BOD removal was recorded at light intensities varying from 45 to 49 x 103 lux, it was found that the magnitude of diurnal oxygenation is influenced more by variation in algal population than by changes in the light intensity. Euglena and other motile pond algae adopted to the varying pond conditions, these make the pond surface to appear green in the morning and grey during the period of intense radiation. It was established that presence of a few algal species indicated incomplete stabilization whereas larger varieties were indicative of complete stabilization. Daphnia species infested the ponds in the beginning of summer, their population was controlled by sprinkling lime powder on the pond dikes. It was observed that ponds with weedless dikes appeared to have an extremely high chance of free from mosquito breeding. Die-away rates for Coliform and E. Coli organism were also investigated

Eutrophication in waste stabilization ponds treating domestic sewage

Eutrophication was frequently observed in waste stabilization ponds treating domestic sewage in the hot summer months of May, June and July. Due to eutrophication the pond efficiency was greatly reduced. During this period the ability of the ponds to reduce nutrients was also affected. Different methods were tried for measuring eutrophication in the ponds, some of these include, measurement of light penetration, calculation of productivity index and counting of algal cells. Also health aspects of eutrophication and aquatic plant nutrients considered to be most significant for algal growth were discussed