The synthesis of ectoine enhance the assimilation of ammonia nitrogen in hypersaline wastewater by the salt-tolerant assimilation bacteria sludge.

In contrast to nitrification-denitrification microorganisms that convert ammonia nitrogen in hypersaline wastewater into nitrogen for discharge, this research utilizes sludge enriched with salt-tolerant assimilation bacteria (STAB) to assimilate organic matter and ammonia nitrogen in hypersaline wastewater into ectoine - a biomass with high economic value and resistance to external osmotic pressure. The study investigates the relationship between the synthesis of ectoine and nitrogen removal efficiency of STAB sludge in three sequencing batch reactors (SBR) operated at different salinities (50, 75, and 100 g/L) and organic matter concentrations. The research reveals that, under low concentration carbon sources (TOC/N = 4, NH4+-N = 60 mg/L), the ammonia nitrogen removal efficiency of SBR reactors increased by 14.51 % and 17.25 % within 5 d and 2 d, respectively, when salinity increased from 50 g/L to 75 g/L and 100 g/L. Under high concentration carbon sources (TOC/N = 8, NH4+-N = 60 mg/L), the ammonia nitrogen removal efficiency of STAB sludge in the three reactors stabilized at 80.20 %, 76.71 %, and 72.87 %, and the total nitrogen removal efficiency was finally stabilized at 80.47 %, 73.15 %, and 65.53 %, respectively. The nitrogen removal performance by ammonium-assimilating of STAB sludge is more sustainable under low salinity, while it is more short-term explosive under high salinity. Moreover, the intracellular ectoine concentration of STAB sludge was found to be related to this behavior. Empirical formulas confirm that STAB sludge synthesizes ectoine from nutrients in wastewater through assimilation, and intracellular ectoine has a threshold defect (150 mg/gVss). The ectoine metabolism pathways of STAB sludge was constructed using the Kyoto Encyclopedia of Genes and Genomes (KEGG). The ammonia nitrogen in sewage is converted into glutamic acid under the action of assimilation genes. It then undergoes a tricarboxylic acid cycle to synthesize the crucial precursor of ectoine - aspartic acid. Subsequently, ectoine is produced through ectoine synthase. The findings suggest that when the synthesis of intracellular ectoine reaches saturation, it inhibits the continuous nitrogen removal performance of STAB sludge under high salinity. STAB sludge does not actively release ectoine through channels under stable external osmotic pressure.

Optimizing heterotrophic nitrification process: The significance of demand-driven aeration and organic matter concentration.

Heterotrophic nitrification and aerobic denitrification (HNAD) sludge were successfully acclimated. The effects of organics and dissolved oxygen (DO) on nitrogen and phosphorus removal by the HNAD sludge were investigated. The nitrogen can be heterotrophically nitrified and denitrified in the sludge at a DO of 6 mg/L. The TOC/N (total organic carbon to nitrogen) ratio of 3 was found to result in removal efficiencies of over 88% for nitrogen and 99% for phosphorus. The use of demand-driven aeration with a TOC/N ratio of 1.7 improved nitrogen and phosphorus removal from 35.68% and 48.17% to 68% and 93%, respectively. The kinetics analysis generated an empirical formula, Ammonia oxidation rate = 0.08917·(TOC·Ammonia)0.329·Biomass0.342. The nitrogen, carbon, glycogen, and poly-ß-hydroxybutyric acid (PHB) metabolism pathways of HNAD sludge were constructed using the Kyoto Encyclopedia of Genes and Genomes (KEGG). The findings suggest that heterotrophic nitrification precedes aerobic denitrification, glycogen synthesis, and PHB synthesis.

Effects of Pressurized Aeration on the Biodegradation of Short-Chain Chlorinated Paraffins by Escherichia coli Strain 2.

Short-chain chlorinated paraffins (SCCPs) were defined as persistent organic pollutants in 2017, and they can migrate and transform in the environment, accumulate in organisms, and amplify through the food chain. Although they pose a serious threat to environmental safety and human health, there are few papers on their removal. The current SCCP removal methods are expensive, require severe operating conditions, involve time-consuming biological treatment, and have poor removal specificities. Therefore, it is important to seek efficient methods to remove SCCPs. In this paper, a pressurized reactor was introduced, and the removal performance of SCCPs by Escherichia coli strain 2 was investigated. The results indicated that moderate pure oxygen pressurization promoted bacterial growth, but when it exceeded 0.15 MPa, the bacterial growth was severely inhibited. When the concentration of SCCPs was 20 mg/L, the removal rate of SCCPs was 85.61% under 0.15 MPa pure oxygen pressurization for 7 days, which was 25% higher than at atmospheric pressure (68.83%). In contrast, the removal rate was only 69.28% under 0.15 MPa air pressure. As the pressure continued to increase, the removal rate of SCCPs decreased significantly. The total amount of extracellular polymeric substances (EPS) increased significantly upon increasing the pressure, and the amount of tightly bound EPS (TB-EPS) was higher than that of loosely bound EPS (LB-EPS). The pressure mainly promoted the secretion of proteins in LB-EPS. Furthermore, an appropriate pure oxygen pressure of 0.15 MPa improved the dehydrogenase activity. The gas chromatography-mass spectrometry (GC-MS) results indicated that the degradation pathway possibly involved the cleavage of the C-Cl bond in SCCPs, which produced Cl-, followed by C-C bond breaking. This process degraded long-chain alkanes into short-chain alkanes. Moreover, the main degradation products detected were 2,4-dimethylheptane (C9H20), 2,5-dimethylheptane (C9H20), and 3,3-dimethylhexane (C8H18).

Study on the Control of Dichloroacetonitrile Generation by Two-Point Influent Activated Carbon-Quartz Sand Biofilter.

Aiming at the problem of highly toxic Nitrogenous disinfection by-products (N-DBPs) produced by disinfection in the process of drinking water, two-point influent activated carbon-quartz sand biofilter, activated carbon-quartz sand biofilter, and quartz sand biofilter are selected. This study takes typical N-DBPs Dichloroacetonitrile (DCAN) as the research object and aromatic amino acid Tyrosine (Tyr), an important precursor of DCAN, as the model precursor. By measuring the changes of conventional pollutants in different biofilters, and the changes of Tyr, the output DCAN formation potential of the biofilters, this article investigates the control of DCAN generation of the two-point influent activated carbon-quartz sand biofilter. The results show that the average Tyr removal rate of the three biofilters during steady operation is 73%, 50%, and 20%, respectively, while the average effluent DCAN generation potential removal rate is 78%, 52%, and 23%, respectively. The two-point influent activated carbon-sand biofilter features the highest removal rate. The two-point water intake improves the hypoxia problem of the lower filter material of the activated carbon-quartz sand biofilter, and at the same time, the soluble microbial products produced by microbial metabolism can be reduced by an appropriate carbon sand ratio, which is better than traditional quartz sand filters and activated carbon-quartz sand biofilters in the performance of controlling the precursors of N-DBPs.

Effect of the rapid increase of salinity on anoxic-oxic biofilm reactor for treatment of high-salt and high-ammonia-nitrogen wastewater.

The washing wastewater from the desulfuration and denitration of power plants has high salt (chloride and sulfate) and ammonia-nitrogen concentrations and is difficult to treat using microbiological methods. A novel anoxic/oxic biofilm process was developed to remove ammonia from wastewater. Three rapid strategies (sulfate concentration was increased from 0 to 60 g/L in 6, 13, and 22 days (R1, R2, and R3, respectively)) were applied and produced biofilm with the same nitrification capacity as slow strategies (100-203 days). Excessive organics inhibited the nitrification capacity of the biofilm. R1 excelled at ammonia removal (from 30% to 95%, 70 mg/(L·d), with an effluent ammonia concentration of 4 mg/L) at 60 g/L salinity after the organic load was reduced. The content of extracellular polymeric substances in biofilm depended on its capacity to remove organics. Pseudomonas and Thauera were enriched in the three reactors. Controlling the organic load might prevent the sulfur cycle.

Performance and Microbial Community of Different Biofilm Membrane Bioreactors Treating Antibiotic-Containing Synthetic Mariculture Wastewater.

The performance of pollutant removals, tetracycline (TC) and norfloxacin (NOR) removals, membrane fouling mitigation and the microbial community of three Anoxic/Oxic membrane bioreactors (AO-MBRs), including a moving bed biofilm MBR (MBRa), a fixed biofilm MBR (MBRb) and an AO-MBR (MBRc) for control, were compared in treating antibiotic-containing synthetic mariculture wastewater. The results showed that MBRb had the best effect on antibiotic removal and membrane fouling mitigation compared to the other two bioreactors. The maximum removal rate of TC reached 91.65% and the maximum removal rate of NOR reached 45.46% in MBRb. The addition of antibiotics had little effect on the removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N)-both maintained more than 90% removal rate during the entire operation. High-throughput sequencing demonstrated that TC and NOR resulted in a significant decrease in the microbial diversity and the microbial richness MBRs. Flavobacteriia, Firmicutes and Azoarcus, regarded as drug-resistant bacteria, might play a crucial part in the removal of antibiotics. In addition, the dynamics of microbial community had a great change, which included the accumulation of resistant microorganisms and the gradual reduction or disappearance of other microorganisms under antibiotic pressure. The research provides an insight into the antibiotic-containing mariculture wastewater treatment and has certain reference value.

Membrane fouling mitigation in different biofilm membrane bioreactors with pre-anoxic tanks for treating mariculture wastewater.

This study compared the membrane fouling mitigation in two novel types of biofilm membrane bioreactor coupled with a pre-anoxic tank (BF-AO-MBR)-namely a fixed biofilm membrane bioreactor (FB-MBR) with fiber bundle bio-carriers and a moving-bed biofilm membrane bioreactor (MB-MBR) with suspended bio-carriers-relative to an anoxic/oxic MBR (AO-MBR), at salinities ranging from zero to 60 g/L. The results showed that the FB-MBR mitigated membrane fouling to a greater degree than the MB-MBR and AO-MBR. During operation, the FB-MBR exhibited the lowest fouling development, with three membrane filtration cycles, while the AO-MBR and MB-MBR had 22 and nine cycles, respectively. The key fouling factor in all reactors was cake layer resistance (RC), which contributed to 89.61, 62.20, and 83.17% of the total fouling resistance (RT) in AO-MBR, FB-MBR and MB-MBR, respectively. Additionally, in the FB-MBR, the pore blocking resistance (30.07%) was also an important cause of fouling. Fiber bundle bio-carriers and suspended bio-carriers reduced the RT by 37.68% and 21.24% (mainly the RC) compared to that of AO-MBR. Furthermore, FB-MBR and MB-MBR caused a decrease of suspended biomass (80.14 and 15.90%, respectively), and the latter exhibited a higher sludge particle size than AO-MBR, possibly resulting in the cake layer decline. The studied BF-AO-MBRs further alleviated the fouling propensity by reducing the amount of soluble microbial product (SMP) and extracellular polymeric substances (EPS) under all salinity levels, especially the FB-MBR. Among the protein components, the amounts of tryptophan protein-like substance and aromatic protein-like substance were significantly lower in the FB-MBR compared to the AO-MBR and MB-MBR. Additionally, at 60 g/L salinity, the structure of the microbial community in the FB-MBR had a lower abundance of Bacteroidetes and more biomacromolecule degraders, which may have contributed to the moderation of membrane fouling.