Effluent Treatment and Residuals Management Using Land Applica

AquaFuture operates a 1.8 million gallon recirculating aquaculture facility capable of filtering the waste products from over three quarters of a million fish that are fed over one million pounds of feed per year. This paper describes a compact system for effluent treatment and residuals management that has proven effective at maintaining water quality within compliance limitations. Solids are removed from the fish culture systems via microscreen filters. Waste water generated from the backwash of microscreens is a moderately high strength effluent which is treated via specially designed settling basins for TSS removal, a biofilter for BOD removal, and a microscreen for polishing prior to final ozonation for potential pathogens reduction. This system has proven effective at achieving over 95% BOD and TSS removal from the process effluent. Solids generated from the operation of the effluent treatment system are stored for seasonal land application in conjunction with normal planting and harvest cycles. An economic analysis of the fertilizer value of fish manure versus other available fertilizers for organic and conventionally grown crops is presented. Despite its relatively high nutritive value, fish manure in a slurry form (about 14% solids) has limited economic value unless the expense of hauling can be mitigated by spreading it on suitable crops within a short distance from the farm. Odors produced by spreading fish manure poses a special management problem that is best addressed by injection or immediately tilling the soil after spreading.