Investigation on effects of common carp (Cyprinus carpio) and the silver carp (Hypophthalmichthys molitrix) presence on qualitative incises of the wastewater (Case study: Semnan wastewater treatment plant)

This study aimed to investigate weight gain and survival of silver carp and common carp species in urban wastewater at supplementary treatment stage and their effects on wastewater qualitative parameters, including as BOD, COD, TSS and TDS. This study was performed with a control treatment without the presence of fish and other treatments contained two species of common carp and silver carp as triplicate with 30±5 and 60±5 gr. The research period was 30 days and at intervals of 10 days from the start of the study, sampling and analysis of wastewater samples was carried out. According to the results, the highest weight gain (8.3%) and the highest mortality rates (20 %) during the research period attributed to the treatment of silver carp was 30±50. All treatments (control as an exception) caused significant reduction in BOD, COD and TSS parameters during sampling process (P<0.05) showed a decreasing trend. The MPN factor didn’t show any significant differences among the treatments. At the end of the research period, the best performance in improving wastewater quality parameters related to the treatment of silver carp 60±5 gr. In this treatment, TSS reduction efficiency was 55-50% during the research period in addition to TSS reduction with absorption of suspended materials in body and production of less waste, the least TDS parameter was recorded in this treatment.