SEDIMENTATION PROPERTIES OF AQUACULTURE WASTEWATER SLUDGE DURING THE CULTIVATION OF CLARIAS GARIEPINUS

The aim of the article is to study the parameters of wastewater settling in recirculating aquaculture systems (RAS) during the cultivation of African sharptooth catfish. The volumes of freshwater fish farming using such systems are steadily increasing. However, RAS have a disadvantage in that they require the disposal of contaminated wastewater generated during the washing of the filter meshes of the me-chanical filters through which the recirculated water passes. It is advisable to use wastewater settling tanks in RAS be-cause they are quite effective in removing total suspended solids (TSS) and have a relatively low cost, which leads to their high economic efficiency. The results of studies on the settling of wastewater from mechanical filters using RAS during the cultivation of Clarias gariepinus confirmed the possibility of carrying out this process with high efficiency and using simple equipment in the case of further utilization of sludge and settled wastewater. The TSS content in the settled wastewater after the settling tank was 0.07±0.015 g/l, while the TSS content in the recircu-lating water after the mechanical filter was 0.057±0.023 g/l, which allows the use of the settling tank to replace the mechanical filter for RAS during the cultivation of Clarias gariepinus. Such a replacement will make it possible to remove only the sludge from the RAS, with its amount not exceeding 7 % of the amount of mechanical filter flush water. The expediency of creating a settling system based on two settling tanks was established: the first one for settling the wastewater from mechanical filters and the second one for settling the sludge obtained at the first stage of settling, which will reduce the amount of sludge for further utilization to 3 % of the amount of waste rinse water from mechanical filters. The settled wastewater from the settling tanks can be used in hydroponics systems or for irrigation, and the sludge after two-stage settling can be used for biogas production.