Optimizing Hydraulic Retention Time and Area of Biological Settling Ponds for Super-Intensive Shrimp Wastewater Treatment Systems

Abstract

Biological settling ponds are a practicable approach for treating super-intensive shrimp aquaculture wastewater for almost all shrimp producers in the Vietnamese Mekong Delta (VMD). The optimization of the hydraulic retention time (HRT) of biological settling ponds plays a crucial role in establishing the stability of outflow wastewater quality and suitability of the settling pond area (SPA). This study aims to suggest appropriate HRT and SPA for super-intensive shrimp wastewater treatment systems based on the National Standard (QCVN 02-19:2014/BNNPTNT) and the best aquaculture practices (BAP) standards and guidelines. We investigated 20 typical super-intensive shrimp farms in the VMD and collected effluent samples from siphoning process, daily water exchange, and outflow of biological effluent-treatment settling ponds. The results showed that the average of each super-intensive shrimp farm produced wastewater at approximately 218 m3 ha−1 day−1. The contaminant loads of TSS, COD, TKN, and TP were commensurate to 177, 113, 9.86, and 4.19 kg ha−1 day−1, respectively. Based on the relationship between outflow COD, TSS concentrations, and HRT of biological-surveyed settling ponds, a 13.4-day HRT and 1934-m2 SPA were suggested to optimize the super-intensive shrimp wastewater treatment systems. Our recommendation for further work is to continuously optimize the HRT and SPA rates of functional ponds (anaerobic, facultative, and maturation) to ameliorate the engineering configuration of the recommended biological settling pond.

Treatment of sludge from intensive whiteleg shrimp farming using a sequencing batch reactor

“…Previous publications have revealed that the ISF wastewater (including wastewater from water exchange and sludge from siphoning) from intensive and super-intensive shrimp farming often contains high levels of biodegradable organic compounds and dissolve nutrients (Boopathy, 2018;Nguyen et al, 2022;. Average COD levels were in the 466 -1,854 mg/L range; while concentrations of TAN, TKN, and TP were in a typical range of 29.8 -101 mg/L, 9.63 -161 mg/L, & 17.3 -92 mg/L, respectively (Boopathy, 2018;Tran et al, 2022;Nguyen et al, 2022). The sludge characteristics in this study were much higher than the results of previous studies.…”

“…Shrimps were intensively cultured according to a three-stage process with an initial stocking density of 1,000 fish/m 2 and gradually decreasing stocking density to about 400 -500 shrimp/m 2 in stage 2 and about 150 -200 shrimp/ nutrients. Investigating 20 typical ISF ponds in the MK, Tran et al (2022) reported that average levels (mg/L) of total suspended solid (TSS), chemical oxygen demand (COD), total ammonia nitrogen (TAN), total Kjeldahl nitrogen (TKN), total phosphorous (TP) in sludge were 3. 423, 1.854, 101, 161, and92, respectively.…”