Single-sludge denitrification in recirculating aquaculture systems: Effects of pre-fermentation and pH

Karin Isabel Suhr, Carlos Octavio Letelier Gordo, Pau Prat Busquets

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Abstract

Single-sludge denitrification (DN) reactors in aquaculture utilize the solid fish waste produced in the system to reduce the nitrate load discharged. The solid waste is available for denitrifiers when present in soluble readily biodegradable form. A transformation accomplished by bacterial hydrolysis (and fermentation). The objective of this study was to quantify the effect of pre-fermentation of the solid fish waste on single-sludge DN-reactor efficiency. Pre-fermentation times tested were; 0 (no pre-fermentation), 1 d, 5 d, and 10 d. The efficiency was quantified as the potential DN-rates in laboratory assessments. Results showed that the highest DN-rate obtained was achieved by 1 d pre-fermentation. The volumetric DN-rate measured in decreasing order was; 23.4 ± 0.00 (1 d); 20.5 ± 0.35 (5 d); 17.0 ± 0.47 (10 d); 14.2 ± 0.24 (0 d) mg NO3-N (L∗h)-1 It was suspected that the poor utilization of sCOD in 5 and 10 d pre-fermentation treatments were due to low start pH (below 7). Subsequently, the experiments were repeated in 0.1 M HEPES buffer pH=7.1, and showed a clear correlation between specific DN-rate and soluble COD content. Overall, the highest increase in potential specific DN-rate was achieved by applying pre-fermentation, e.g. from 0 d to 1 d the increase was 85 % and 106 % at unadjusted pH and pH 7.1, respectively. Additional 20 % increase was achieved at pH 7.1 by prolonging the pre-fermentation time to 5 d. At unadjusted pH conditions, the higher sCOD obtained by longer pre-fermentation was futile due to inhibitory effect of low pH
Original languageEnglish
Title of host publicationProceedings / American Society of Agricultural and Biological Engineers Annual International Meeting 2014
PublisherAmerican Society of Agricultural and Biological Engineers
Publication date2014
Pages3050-3057
ISBN (Print)978-163266845-5
Publication statusPublished - 2014
EventAnnual International Meeting of the American Society of Agricultural and Biological Engineers Joint with the Canadian Society of Biological Engineers - , Canada
Duration: 13 Jul 201416 Aug 2014

Conference

ConferenceAnnual International Meeting of the American Society of Agricultural and Biological Engineers Joint with the Canadian Society of Biological Engineers
CountryCanada
Period13/07/201416/08/2014

Cite this

Suhr, K. I., Letelier Gordo, C. O., & Prat Busquets, P. (2014). Single-sludge denitrification in recirculating aquaculture systems: Effects of pre-fermentation and pH. In Proceedings / American Society of Agricultural and Biological Engineers Annual International Meeting 2014 (pp. 3050-3057). American Society of Agricultural and Biological Engineers.