Abstract
Aquaculture effluents with high concentration of nitrogen and phosphorus compounds can cause negative impacts on the environment and aquatic wildlife. This trial evaluated the possibility to treat sludge collected from intensive ponds for black tiger prawn Penaeus monodon. The experimental sludge contained 2,150 ± 282 mg/L COD, 9.4 ± 1.0 mg/L ammonia–nitrogen, 0.5 ± 0.1 mg/L nitrite–nitrogen (NO2−–N), 7.1 ± 2.8 mg/L nitrate–nitrogen (NO3−–N), 2.83 mg/L PO43−–P (phosphate–phosphorus). Anaerobic treatment was applied using a commercial probiotics (Wawiz Greezon, Green Guard Biotechnology Co.) for 4 weeks at 0.1 ppt weekly. Sampling was conducted every seven days to monitor ammonia-N, nitrite, nitrate, phosphorus, COD and microbial structure.
Results showed that the probiotics treatment removed completely (100%) ammonia and 89.6% phosphorus from the sludge when the concentration of these two parameters remained high in the control. Nitrite and nitrate slightly increased in the probiotics treatment in the first week but gradually declined towards the end of the trial. The variable regions V1-V3 of the 16S r RNA gene was amplified by PCR and was sent to AGRF for paired-end sequencing 300 bp paired end chemistry on the Illumina MiSeq platform (Illumina). Within a week, probiotics treatment significantly drove microbial community to divert from the control group and the initial bacterial composition. These changes did not occur to most of the dominant taxa of the bacteria as the top three phyla (Chlorobi, Proteobacteria and Bacteroidetes) were relatively persisted. These results indicate that even with the low abundance in the community, probiotic bacteria still showed their high effectiveness in removing nitrogen and phosphorus waste from prawn farming wastewater. These results suggest that using anaerobic probiotics can be used effectively for sludge treatment in intensive shrimp farming.
Key words: wastewater, sludge, Penaeus monodon, nitrogen removal, probiotics, microbiome