Biochemical Oxygen Demand in Channel Catfish Ictalurus punctatus Pond Waters

Abstract

AbstractA study of the biochemical oxygen demand (BOD) of waters from ten channel catfish ponds at Auburn, Alabama, revealed that the 5‐d BOD (BOD5) seldom exceeded 8 mg/L and that the ultimate BOD (BODu) was usually less than 30 mg/L. Water samples from catfish ponds usually needed to be diluted only 2 or 3 times to permit BOD5 measurements, and nitrification occurred even during a 5‐d incubation period. Catfish pond waters were not extremely high in ammonia nitrogen concentration, and ammonia nitrogen introduced in the ammonium chloride‐enriched dilution water caused an appreciable increase in BOD of some samples. Plankton respiration is a major component of carbonaceous BOD (CBOD) in catfish pond waters. Thus, the BOD is not expressed as rapidly during 5‐d incubations as in typical waste‐water. The ultimate BOD (BODu) would be a good measurement of oxygen demand for catfish pond effluents, but it is difficult to measure. Data from this study suggest that BODu can be estimated from BOD5, but the correlation is not strong (R2= 0.62). An alternative is to develop a short‐term BOD measurement specifically for effluents from channel catfish and other aquaculture ponds. This study suggests that a 10‐d BOD conducted without nitrification inhibition or addition of ammonia nitrogen in dilution water might be a better alternative to standard BOD5 or BODu measurements normally used in wastewater evaluation.