Effect of solar light on the decrease of microbial contamination in facultative stabilization pond

One of the indexes of stabilization pond is the presence of coliform bacteria in water and wastewater. This study aimed to determine the effect of solar light on coliform variations in stabilization pond. In this experimental study, the effect of light, pH (<7, 7.1–8, 8.1–9), and temperature (10 ºC and 30 ºC) on facultative stabilization pond was studied for six months. The sampling was accomplished weekly. Coliform colonies were measured using the nine tube fermentation method. The coliform deterioration constant was calculated using the Maraise model. The data were analyzed using SPSS version 20. The effect of light on coliform deterioration constant was negative. Also, low pH increased the coliform death. No significant statistical difference was seen at 10 ºC and 30 ºC (P < 0.05). Low temperature cannot be adherence for facultative stabilization pond. Regarding the positive effect of temperature on the coliform death, use of facultative stabilization pond in a warm climate is suggested.