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
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