Treatment of aquaculture wastewater effluents using slow filtration

Abstract

Aquaculture wastewater effluents may cause many environmental problems to the receiving water. Therefore, wastewater from aquaculture facilities must be effectively manage to remove dissolved wastes and suspended solids that can be pollute receiving bodies of water. Effective technologies and low cost medium filters are needed to treat the effluents from fish farm. The study was conducted to evaluate the effectiveness of slow filtration as treatment option for removing total ammonia nitrogen, nitrite, total suspended solids (TSS), turbidity and biological oxygen demand (BODS) from aquaculture wastewater effluents. Malaysia has a great potential in palm oil plantation (29.8 million tones are produced annually). Industrial wastes such as burnt oil palm shells can be utilize as a media option to reduce production cost with higher profit for aquaculture wastewater management. In this study, sand and burnt oil palm shells (BOPS) were used as dual media at constant effective size (i.e. ES of 0.5 mm for sand and ES of 1.0 mm for BOPS) with same uniformity coefficient of 1.5. BOPS are a solid waste derived from the final processing of local oil palm industry while sand media is a well known effective media for slow filtration. The performance of slow filtration was evaluated using two different flow rates that 0.2 m3/m2/hr and 2.0m3/m2/hr. Greater removal of TAN, nitrite, turbidity and suspended solids was obtained for both flow rates evaluation. However, the slow filters are not effective on reducing the BODS from the water inlet since there is no pre-filtered of aquaculture wastewater prior to treatment. The slow filters removed 82.40% and 79.97% of TAN for flow rates of 0.2 m3/m2/hr and 2.0m3/m2/hr, respectively. Outlet nitrite-nitrogen was reduced to 0.139±0.010 mg/L for 0.2m3/m2/hr and 0.185±0.012 mg/L for 2.0m3/m2/hr. The highest percentage of removing suspended solids was recorded on flow rate of 0.2 m3/m2/hr with 90.53% compared to 2.0m3/m2/hr with 86.24%. Turbidity for outlet of both flow rates reduced to 41.65±5.68 NTU and 139.03±22.16 NTU, respectively. Meanwhile, all of water quality measured except BODS showed a significantly different between inlet and outlet for both flow rates. Results also indicate that 0.2 m3/m2/hr is more effective for removing the dissolved waste and suspended solids from inlet compared to flow rate of2.0m3/m2/hr.