Impact of ozonation and residual ozone-produced oxidants on the nitrification performance of moving-bed biofilters from marine recirculating aquaculture systems.

Schroeder, J. P., Klatt, S .F., Schlachter, M., Zablotski, Yury, Keuter, S., Spieck, E. and Schulz, Carsten (2015) Impact of ozonation and residual ozone-produced oxidants on the nitrification performance of moving-bed biofilters from marine recirculating aquaculture systems. Aquacultural Engineering, 65 . pp. 27-36. DOI 10.1016/j.aquaeng.2014.10.008.

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Abstract

In marine recirculating aquaculture systems (RAS) ozone is often used in combination with biofiltration for the improvement of process water quality. Especially for disinfection purposes ozone residuals are required, that lead to a fast formation of secondary oxidants in seawater, summed up as ozone-produced oxidants (OPO). We studied the impact of OPO on nitrifying biofilter bacteria in a series of laboratory batch experiments by exposing (i) cell suspensions of the ammonia-oxidizing bacteria (AOB) Nitrosomonas marina strain 22 and the nitrite-oxidizing bacteria (NOB) Nitrospira strain Ecomares 2.1, (ii) a pure culture of the NOB Nitrospira strain immobilized on biocarriers, as well as (iii) a heterogeneous biofilm culture settled on biocarriers from a marine RAS for 1 h to different OPO concentrations up to 0.6 mg/l chlorine equivalent. Subsequent activity tests detected a negative linear correlation between OPO concentration and nitrifying activity of suspended pure cultures. Immobilization on biocarriers increased the tolerance of AOB and NOB dramatically, suggesting the biofilm matrix to be highly protective against OPO. Furthermore, we investigated the chronic effect of moderate ozonation at OPO concentrations of 0, 0.05, 0.10 and 0.15 mg/l chlorine equivalent on biofilter performance in a 21 d exposure experiment using 12 experimental RAS, stocked with tilapia (Oreochromis niloticus). Chronic exposure experiments could not reveal any harmful impact on biofilter performance for OPO concentrations up to 0.15 mg/l, even at continuous exposure. Surprisingly, nitrifying activity was enhanced at all OPO concentrations compared to the control without ozonation, suggesting moderate ozonation to promote biological nitrification. It can be concluded that rather health, welfare and performance of most cultivated fish species are the limiting factors for ozone dosage than nitrification performance of biofilters. The results may further have practical implications in relation to design and operational strategy of water treatment processes in RAS and might thus contribute to the optimization of an effective and safe treatment combination of biofiltration and ozonation

Document Type: Article
Additional Information: WOS:000352666800005
Keywords: Ozone; Oxidants; Nitrification; Bacteria; Biofilter; RAS
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence > FO-R04
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.aquaeng.2014.10.008
ISSN: 0144-8609
Projects: Future Ocean
Date Deposited: 04 May 2015 08:18
Last Modified: 19 Dec 2017 12:49
URI: http://oceanrep.geomar.de/id/eprint/28715

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