Heterotrophic bacterial production on solid fish waste: TAN and nitrate as nitrogen source under practical RAS conditions.
The drumfilter effluent from a recirculation aquaculture system (RAS) can be used as substrate for heterotrophic bacteria production. This biomass can be re-used as aquatic feed. RAS effluents are rich in nitrate and low in total ammonia nitrogen (TAN). This might result in 20% lower bacteria yields, because nitrate conversion into bacteria is less energy efficient than TAN conversion. In this study the influence of TAN concentrations (1, 12, 98, 193, 257mgTAN/l) and stable nitrate-N concentrations (174+/-29mg/l) on bacteria yields and nitrogen conversions was investigated in a RAS under practical conditions. The effluent slurry was supplemented with 1.7gC/l sodium acetate, due to carbon deficiency, and was converted continuously in a suspended bacteria growth reactor (hydraulic retention time 6h). TAN utilization did not result in significantly different observed yields than nitrate (0.24-0.32gVSS/gC, p=0.763). However, TAN was preferred compared to nitrate and was converted to nearly 100%, independently of TAN concentrations. TAN and nitrate conversions rates were differing significantly for increasing TAN levels (p<0.000 and p=0.012), and were negatively correlated. It seems, therefore, equally possible to supply the nitrogenous substrate for bacteria conversion as nitrate and not as TAN. The bacteria reactor can, as a result, be integrated into an existing RAS as end of pipe treatment.
Schneider
Oliver
O
Aquaculture and Fisheries Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands. oliver.schneider@wur.nl
Sereti
Vasiliki
V
Eding
Ep H
EH
Verreth
Johan A J
JA
D000641:Ammonia / Q000032:analysis*; D000818:Animals; D017756:Aquaculture; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D001673:Biodegradation, Environmental; D018533:Biomass; D005399:Fishes / Q000378:metabolism*; D052836:Heterotrophic Processes; D009566:Nitrates / Q000032:analysis*; D012037:Refuse Disposal; D014866:Waste Products
D009566:Nitrates; D014866:Waste Products; D000641:Ammonia