Performance Evaluation of Collard Based Bio-Filter for Treating Fish Effluent for Re- use

Abstract

Abstract: The increasing Uganda’s urban population growth has led to limited space coupled with high cost of living, thus making it difficult for the urban poor in congested areas to afford fish protein hence poor nutrition among the low income earners. Therefore this study was conducted to evaluate the performance of collard based bio-filtration system for filtering fish tank effluent for re-use in congested peri-urban areas. Field physical-chemical parameters (ammonia, nitrate, dissolved oxygen, temperature and pH) were measured at various bio-filter lengths in the effluent from both collard based and GBF (Gravel Based Bio-Filter). Differences in mean ammonia and nitrate levels at various lengths were analyzed using one-way ANOVA at p = 0.05. Ammonia levels were significantly reduced (p < 0.05) at various lengths: L0 99.1 mg/L; L1 75.8 mg/L (23.6%); L2 53.1 mg/L (46.4%); L3 25.8 mg/L (74%) and L4 6.6 mg/L (93.4%). Similarly, nitrate levels significantly reduced (p < 0.05): L0 11.8 mg/L; L1 7.2 mg/L (39.4%); L2 3.6 mg/L (69.2%); L3 1.6 mg/L (86.7%) and L4 0.1 mg/L (99.3%). Significant difference (p < 0.05) was obtained in mean ammonia and nitrate removal between collard based and gravel bio-filters. Collard based filter yielded higher ammonia and nitrate removal at L4 by 18.3% and 39.5% respectively, hence L4 is the effective length for collard based bio-filter. Key words: Effluent, bio-filter, nitrifying bacteria, ammonia. 1. Introduction  Globally, the scarcity of fresh water has contributed to increase in reuse of treated effluent in agriculture over the last few decades [1]. Rapid expansion of fish farming due to high demand for fish protein mainly in peri-urban areas has prompted the need for techniques for effective fish effluent treatment for reuse [2]. Fish effluent is poor quality water from fish farm mainly polluted with ammonia, phosphorus and solid matter which becomes toxic to fish [2]. Open disposal of fish effluent not only resulted into environmental pollution, but also restricted future Corresponding author: