Fishpond Effluents Research Articles

A Survey of Water Quality Characteristics of Effluent from Hawaiian Aquaculture Facilities

AbstractTen water quality parameters were measured in influent and effluent water at 11 aquaculture facilities in Hawaii. The data were grouped into four categories based on the types of organisms cultured: freshwater fish, freshwater prawn, marine fish, and marine shrimp. Within each category, concentrations of most parameters were lognormally distributed and spanned one to two orders of magnitude. Geometric mean concentrations of suspended materials, total nitrogen, total phosphorus, and pigments were highest in effluent from freshwater prawn ponds and lowest in marine fish pond effluent. Nitrate/Nitrite and total ammonia concentrations were higher in fish pond effluent than in crustacean pond effluent. Parameter concentrations were generally higher in effluent than in influent water, with freshwater fish and prawn ponds exhibiting the greatest increases in suspended materials and pigments. In contrast, nitrate/nitrite concentrations were lower in effluent than in influent waters. These data provide a basis for analyzing the environmental impacts of warm‐water aquaculture effluent discharges.

Ulva lactuca Biofilters for Marine Fishpond Effluents. II. Growth Rate, Yield and C:N Ratio

The seaweed Ulva lactuca L. was cultured in effluents from intensive marine fishponds in Eilat, Israel. The specific growth rate and the yield of U. lactuca in nutrient-rich fishpond effluents were higher than in pulse- enriched fresh seawater. Both yield and specific growth rate of the seaweed showed positive hyperbolic correlations with N-flux which fitted the Michaelis-Menten kinetics. Maximal dry weight (DW) yield was 55 gm~2d1 and the maximal specific growth rate was 18% d1. The C: N ratio in plant tissue showed a negative hyperbolic correlation with N-flux, dropping from over 15 to approximately 7 (w : w) when grown at low and high N-fluxes, respectively. As the stocking density increased up to 6kgm~ 2 under N-sufficient conditions, both specific growth rate and yield decreased significantly, as did mostly also the C : N ratio. The data suggest the seaweed to be N-limited at low N-fluxes and light limited at high N fluxes, especially at high stocking densities. The high yields obtained show that fishpond effluents supply U. lactuca with all its required nutrients including inorganic carbon. For high yield and high nitrogen content, U. lactuca should be kept at densities of 1 —2 kg m~2 and at ammonia fluxes of about 0.5 moles m~~2 d1. Nitrogen content can be increased further, but at reduced yield, by increasing the stocking density to 4 or 6 kg m~~2.

Ulva lactuca Biofilters for Marine Fishpond Effluents. I. Ammonia Uptake Kinetics and Nitrogen Content

The potential of the seaweed Ulva lactuca as a biofilter for effluents of intensive marine fishponds in arid regions has been studied in Eilat, Israel. One kg (wet wt) nor2 of Ulva in 1 m2 tanks 60 cm deep, removed, during the day, over 90 percent of the ammonia from the fishpond effluents, at inflow fluxes up to 10 μιηο1β5 L1 h1 (0.14 mole m^d1)· At fluxes of 40μπιοΐ68 L1 h~3 (0.58 mole m2d1)9 nearly 40 percent were removed. Night time ammonia removal remained efficient at low ammonia fluxes. Ammonia uptake rate and percent nitrogen (N) in dry weight (DW) of the seaweed showed hyperbolic correlations with ammonia flux through the tanks. The data fitted the Michaelis-Menten kinetics, with a maximal uptake rate of 28 μηιοΐβδ L1 h1 (0.4 mole m~2d1). Pulse ammonia uptake rate was approximately four times that of continuous uptake. Maximal percent N in DW of U. lactuca, when stocked at 1 kg m 2, was 4.07. Increased stocking density (2, 4 and 6 kg m2) did not significantly affect ammonia uptake rate per tank. However, N-content was significantly higher, averaging 5.5 percent of DW. The data indicate that at low ammonia fluxes (below 10 μιηο1β8 L1 h1) U. lactuca was N-limited and that at higher fluxes the algae became gradually light limited. Our results indicate that 10m2 of Ulva biofilter can remove from the effluents of our intensive grow-out ponds over 90 percent of the ammonia produced by 1 kg of daily feed ration or by approximately 75 kg of fish.

The harvest of microalgae from the effluent of a sewagefed high rate stabilization pond by Tilapia nilotica

Abstract There was a linear relationship between maize yield and total nitrogen applied, irrespective of the source of the nutrient: organic (raw sewage, fish pond effluent) or inorganic (commericial fertilizer). An absolute relationship between maize yield and total nitrogen applied could not be developed due to differences in soil fertility (in the experiment apparently due largely to soil physical characteristics). The effluent from the fish ponds contravened the WHO standard of 2 faecal coliforms/100 ml for waste-water reuse for crops eaten cooked and for fish culture. The land required to treat and recycle domestic sewage from a hypothetical city of 100 000 people (design criteria: 40 g BOD 5 and 701 water consumption/person/day i.e., sewage strength 570 mg BOD/1) was estimated at 63 ha. The land area ratios were 1.86 : 1 : 10.25 for the high rate stabilization pond, fish pond, and maize plot, respectively. It is suggested that where land is available in the tropics, wastewater be recycled in a system of conventional stabilization ponds modified for fish cultivation as well as waste treatment. Particular emphasis must be given to public health, pollutants as well as pathogens, in recycled wastewater. Perhaps the only rational way to use a high rate stabilization pond is to harvest the phytoplankton directly from the effluent for use as animal feed.