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Nitrogen pollution in aquaculture needs the efficient and cost-effective in-situ technology. This study aims to apply Marichromatium gracile YL28 to in-situ bioremediation and test its ability to maintain the nitrogen balance in aquaculture. In laboratory aquaculture system, approximately 99.96% of nitrite (1 mg/L) was removed within 7 d through denitrification coupled with assimilatory nitrate reduction. Ammonium (3.5 mg/L) of 95.6% was directly assimilated by YL28 within 7 d. Moreover, in zero exchange water from shrimp (Penaeus vannamei) aquaculture field trials (20 days), YL28 significantly reduced the ammonium accumulation (0.6 mg/L) and 99.3% of nitrite (1.25 mg/L). Toxicological studies with the Institute of Cancer Research (ICR) mice and Oryzias melastigma indicated that M. gracile YL28 can be safely applied in aquatic ecosystems. All results demonstrate that strain YL28 has high promise for future applications of removing inorganic nitrogen and maintaining the nitrogen balance from in-situ aquaculture.

A vertical-flow wetland system was tested for treatment of liquid sludge with high organic concentrations using an organic substrate (peat/crushed pine bark, 1/1) as growing medium. Mesocosms (1 m 3 ) were planted with either Phragmites australis Cav . , Typha latifolia L., or Iris pseudacorus L. The aim of the work was to determine the feasibility of using an organic substrate in treatment wetlands, through the study of its temporal patterns and of its impact on the water output quality. Results confirmed that the organic substrate can be used in such wetlands treating highly organic sludge, without clogging phenomena for the experimental period. The organic substrate released soluble organic matter but few mineral elements. Over the experimental period, substrate TOC concentration did not change while N concentration increased. Plants showed positive impact on substrate temporal patterns and also on the outflow water quality. Overall, Phragmites seemed to be more beneficial than Typha and Iris .