Contribution of Electrolysis within an Integrated System for a Poultry Slaughterhouse Wastewater Treatment

Treatment of poultry slaughterhouse wastewater before disposal or reuse is an essential part of human health and environmental protection in general. This study aimed to investigate the influence of the pre-treatment system based on electrolysis technology within an integrated lab-scale treatment plant in the removal of contaminants from poultry slaughterhouse wastewater. Several treatment units (averaging tank, feather catcher, fat catcher, and coarse mechanical filter) were connected in series before the electrolysis chamber. While in general, the entire integrated system also included some other units such as ultra-filtration, reverse osmosis, and the ultraviolet lamp connected in series. From the analysis results, it was observed that the pre-treatment phase with electrolysis had a significant influence on the general performance of the treatment plant. The pre-treatment contributed to about 33.5% to 100% in the general contaminants’ removal efficiency. The highest contribution was observed from the total chlorine (100%), nitrate (98.2%), as well as BOD (95.3%). The lowest contribution was observed from the nitrite removal, with 33.5%. This study revealed further that the integration of electrolysis technology in a wastewater treatment system has a significant potential for developing an effective wastewater treatment plant.

Strategy for Rapid Recovery of Simultaneous Sulfide and Nitrite Removal under High Substrate Inhibition

The paper deals with the strategy for a quick recovery of reactor treating sulfide and nitrite simultaneously under inhibition caused by high substrate concentration. For influent sulfide concentration of 360 mg S/L, respective sulfide and nitrite removal percentages dropped to 74.19% and 14.33% due to inhibition caused by high sulfide and nitrite concentrations. It was found that reduction in the influent substrate concentration (300 mg S/L) could not revive the nitrite removal performance in 4 days’ operation, which still showed a declining tendency from 47.16–18.52%. Regulating the influent pH around 6.70 ± 0.10, it only took 4 days to recover the performance for 300 mg S/L. Furthermore, at influent sulfide concentration increased to 360 mg S/L, respective sulfide and nitrite removal percentages were 99.76 ± 0.27% and 100%. The strategy of regulating influent pH could recover the process performance in a short term, which would provide great convenience for subsequent process research.

Enriched Microbial Communities for Ammonium and Nitrite Removal from Recirculating Aquaculture Systems

Background: The aim of this study was the enrichment of high-performance microbial communities in biofilters for removal of ammonium and nitrite from aquaculture water. Methods: Ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were enriched from different environmental water samples. The microbial communities with higher ammonium and nitrite removal activity were selected and adapted to different temperatures [9 ºC, 15 ºC, room temperature (25 ºC), and 30 ºC]. The expression of genes involved in nitrification including ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) were measured in temperature-adapted AOB and NOB microbiomes. The microbial species present in the selected microbiomes were identified via 16s rRNA sequencing. Results: The microbial communities containing Nitrosomonas oligotropha and Nitrobacter winogradskyi showed the highest ammonium and nitrite removal activity at all temperatures used for adaptation. Furthermore, the microbial communities do not contain any pathogenic bacteria. They also exhibited the highest expression of AMO and NXR genes. Using the enriched microbial communities, we achieved a 288% and 181% improvement in ammonium and nitrite removal over the commonly used communities in biofilters at 9 °C, respectively. Conclusions: These results suggest that the selected microbiomes allowed for a significant improvement of water quality in a recirculating aquaculture system (RAS).

Enhanced Nitrogen Removal of Wastewater at Low Temperature by Iterative Screening of Cold-Tolerant Denitrifying Bacteria

The biological denitrification for wastewater treatment in winter is often seriously compromised due to the effects of low-temperature (<13 °C) on metabolic activity of microorganism. In this study, an excellent cold-tolerant denitrifying bacterium, Moraxella osloensis LT-01 was isolated by iterative domestication. The strain LT-01 retained about 60% maximal growth activity at 10 °C. Under initial concentrations of 100 mg/L, average ammonium, nitrate and nitrite removal efficiencies for domestic wastewater (C/N 4:1) at 10 °C were 70.35%, 65.39% and 61.74% in 24 h, respectively. Nitrogen balance analysis showed that about 46% of TN was directed toward in the dissimilation form of gas, and 16% of TN was assimilated for cell growth. Key genes hydroxylamine reductase gene (HAO) and nitrite reductase (NirS) involved in nitrification and denitrification processes were identified by gene-specific PCR, indicating that strain LT-01 perform nitrogen removal efficiently via unique simultaneous nitrification and denitrification. These results suggest the bacterium LT-01 has great potential as an effective performer for treating domestic wastewater in winter.