Effect of sunlight on three stratifications of waste water from a waste stabilization pond

Abstract

Experimental studies on stratification were conducted on a waste stabilization pond system at the University of Nigeria, Nsukka, Nigeria. This was done to ascertain the effect of stratification due to sunlight on pond parameters. An experimental approach was adopted which involved pouring wastewater into a glass column apparatus and exposing to sunlight for 7, 14, and 21 days. The statues of 16 physicochemical and microbiological parameters were investigated in the three strata under consideration. Analysis of the samples collected at depths A, B and C, 30cm apart, starting from the top indicated different values of temperature, pH, and nutrients. Maximum values of temperature (32.9 0C), pH (7.9), turbidity (3.46 NTU), and iron (1.86 mg/l), were recorded at the top layer; while the concentration of conductivity (906 μS/cm), total dissolved solids (589 mg/l), BOD5 (400mg/l), ammonia (290 mg/l), total coliform (126,000 cfu/100ml), and E. Coli (99,000 cfu/100ml) were highest at bottom layer. Conductivity, total dissolved solids, turbidity, iron, phosphorus and nitrates fell within World Health Organization (WHO) guidelines. A combination of sunlight with high pH and oxygen concentrations is needed for sunlight to have very significant effects. It is recommended that WSPs be designed with the consideration given to pond dimensions that will provide a wider surface area for sufficient sunlight and oxygen to be acquired.