Sedimentation Characteristics of Suspended Solids in Aquaculture Wastewater of Nile Tilapia Pond

Abstract

【Objective】The deposition and decomposition of solid particles in aquaculture wastewater will lead to the deterioration of aquaculture water and affect the health of fish. The study was conducted to understand the sedimentation rule of solid particles in aquaculture wastewater of Nile tilapia (Oreochromis niloticus) and its influence on the aquaculture water body, with an aim to provide a theoretical basis for the research and development and design of aquaculture wastewater treatment system.【Method】The aquaculture wastewater of Nile tilapia pond was treated by static sedimentation. Samples of aquaculture wastewater at different depths were collected at different sedimentation times, and the particle size distribution, soluble organic components and water quality indexes of aquaculture wastewater were analyzed.【Result】Static sedimentation had no significant effect on the quality of aquaculture wastewater (P > 0.05), and only reduced the mass concentrations of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) in aquaculture wastewater surface. Suspended solids and algae in aquaculture wastewater could be separated by static sedimentation (P < 0.05). After static sedimentation for 5.0 h, the TSS, chlorophyll a mass concentration, turbidity and chromaticity of two-meter-high water decreased by 3 854 mg/L, 42 mg/L, 0.23 NTU and 309 degrees respectively, and the TSS and chlorophyll a mass concentrations in aquaculture water decreased with the extension of sedimentation time. The results of particle size distribution showed that the settleable particles larger than 100 μm could be effectively separated by static sedimentation, but the fine particles lower than 30 μm could not be separated. The sedimentation velocity of solid particles was related to its particle size distribution range and mass concentration. The sedimentation velocity of solid particles decreased with the decrease of particle size distribution range and the increase of mass concentration. The results of three-dimensional fluorescence spectrum showed that the soluble organic compounds in the wastewater of Nile tilapia were mainly fulvic acid-like, and the soluble organic components in the wastewater could not be completely changed by static sedimentation.【Conclusion】Short time static sedimentation can effectively remove settleable particles in aquaculture wastewater, and the mass concentrations of TSS and chlorophyll a decrease with the extension of sedimentation time. However, static sedimentation cannot completely change the soluble organic components in the wastewater, nor can it significantly reduce the mass concentrations of nitrogen, phosphorus and other pollutants in aquaculture wastewater.

Keywords

• oreochromis niloticus
• aquaculture wastewater
• sedimentation separation
• solid particle
• particle size
• soluble organic matter
• wastewater treatment