Efficiency of sewage treatment lagoon on pollution load reduction of Gomishan shrimp farm effluent in Golestan Province

This research was conducted on shrimp farms complex in the northern of Gomishan city, Golestan province. In order to reduce water pollution, around 30 hectares of sedimentation lagoon was constructed on the way of the main outflow channel of shrimp farm. For this project, three sampling stations were considered at the entrance of the shrimp farm, entrance of the lagoon (before entering the lagoon) and way out of the lagoon during the last 3 months of shrimp farming (at the end of August, September and October 2015). Physicochemical parameters including EC, BOD, NO3 and PO4 were measured. The amounts of BOD, nitrate and phosphate ions were not significantly different (P>0.05) at three sampling stations which indicated that the impact of shrimp farming on these factors was not severe. The amounts of these factors at the entrance of the farm were the lowest and at the entrance of the lagoon were the highest. The amounts of these parameters were reduced in lagoon outflow. However, all of these changes were not significantly different from each other (P>0.05). In general, Gomishan shrimp farming with this volume of production and the 30 hectares lagoon is not a serious threat for Gomishan wetland and the Caspian Sea ecosystem. But if the area of shrimp farms increases, some solutions should be found for wastewater treatment because of the increasing possibility of wetland pollution.