Nutrient removal from shrimp farming systems with biofilm associated with the sedimentation basin
Shrimp farming farms with high densities release effluents with high nutrient loads, causing degradation of water quality. This raises concerns about the discharge of crop effluents. In view of this, this work aimed to evaluate the efficiency of an integrated system of sedimentation basin and biofilm in the removal of nutrients. The study was carried out in an open environment for 45 days. Three treatments were used: a) TC treatment, without vertical substrate; b) T50 treatment, internal surface of the boxes increased by 50% and c) T100 treatment, internal surface of the boxes increased by 100%. The boxes were filled with effluent from a shrimp crop. PH, salinity, dissolved oxygen (OD) and temperature were measured daily.During the first 15 days the collections were made every 5 days, after that the collections of water were every 2 days, and biofilm daily. Ammonia analyzes were performed on all sampling days. The analyzes of nitrite, nitrate and phosphate, were made from all collections until the 15th day, and after that period every 6 days. From the biofilm, the dry matter was determined from all collected days. Chlorophyll is analyzed every 5 days. And the estimate of ciliate and flagellate on days 5, 10, 15 and 20. The results showed that the TC and T50 treatments reduced more than 80% of ammonia and phosphate in 10 days. The T100 treatment in the first days showed the lowest values of OD, pH and chlorophyll a, causing a peak in the concentrations of ammonia and phosphate, delaying the removal of these nutrients. For all treatments after the 15th day, the phosphate concentration underwent an increase that was maintained until the end of the experiment. Concluding that when doubling the area available for fixing biofilm there is a difficulty in circulation in the tanks, and an increase in microbial respiration, making the system less efficient. The sedimentation basin without biofilm, or with 50% addition of substrate, both are efficient. Therefore, the effluent must remain in the sedimentation basin for a minimum of 10 days, but not exceeding 15 days, so that there is no increase in phosphate levels.