Fluctuation of organic substances, solids, protozoan cysts, and parasite egg at different units of a wastewater integrated stabilization pond (full scale treatment plant): a case study, Iran

Abstract

Appropriate treatment of wastewater and achieving desired standards are among the important objectives in wastewater treatment. The amount of organic compounds (BOD & COD), suspended solids, protozoa cysts, and parasites are different in each of these units, due to different conditions of treatment and design parameters on the stabilization pond units. The aim of this study was to determine changes of the mentioned parameters in a series of stabilization pond units in a real scale. This descriptive–analytical study was conducted on 64 samples collected in both warm and cold periods. Measurement of the parameters and parasitic analysis were done based on water and wastewater standard and Bailenger methods, respectively. Results showed no significant difference in the mean of total efficiency removal of any parameters between every two ponds with each other. Further, there was significant difference in the efficiency removal of all parameters in three ponds (anaerobic, primary, and secondary facultative), except soluble COD removal of warm season between anaerobic and primary facultative ponds, TDS of warm season between primary and secondary facultative ponds, and TDS of cold season between anaerobic and primary facultative ponds) p < 0.05). Also, changes of the trend for all the measured parameters of the system were decreasing, and efficiency removal of protozoan cysts and parasites was 100%. According to the results, it can be said that the anaerobic pond had a greater role than the facultative ponds in terms of reducing organic and parasitic parameters; but, to reach the effluent standards, a facultative pond was needed after the anaerobic pond.