C Max Bio Sciences

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WATER TREATMENT IN AQUACULTURE(SOLID REMOVAL)

The metabolic activity involved in converting fish feed to fish flesh produces waste products. These consist of suspended solids (SS) and dissolved nutrients. Suspended solids amount to approximately 25% of the feed used, on a dry matter basis. The principles involved are applicable to both flow-through and recirculation farms. Removal of suspended solids from flow-through fish farms has different requirements from other water treatment processes such as those handling sewage, pig farm effluent or dirty water from a vegetable processing plant: concentrations of pollutants in fish farm effluent are relatively low and flow volumes are relatively high. These large water flow volumes require careful choice of systems to control costs
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ORIGIN OF SUSPENDED SOLIDS

In a farm, suspended solids and dissolved nutrients originate from:
• Uneaten feed
• Fish metabolism producing faeces
• Solids carried into the farm with the flow from the external water source
• Growth of micro-algae and bacteria
FACTORS EFFECTING PRODUCTION OF SUSPENDING SOLIDS
Production of suspended solids within a fish farm is affected by a range of factors, including:
• Feed quality
• Rate of feeding
• Feeding method
• Water exchange rate - Tank hydrology
• Fish stocking density
• Dissolved oxygen level
• Efficiency of farm management and skills of personnel
The amount of uneaten feed can be reduced by a careful feeding regime that provides the correct amount of feed, at the time the fish require it, and by husbandry that provides water quality suitable for feed conversion. Substantial improvements in feed conversion ratios, and reductions in the faeces generated, have been achieved by improving fish diets; for example, by using ingredients with high digestibility and diets that are matched to the requirements of the fish species. Selection of feed ingredients can influence the physical stability of faeces on their journey to the point where they are removed by sedimentation or filtration.