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

Impact of typhoon on nutrient contaminants, antibiotic resistance genes and microbial communities in mariculture tailwater treatment system

Intensive marine aquaculture generates complex pollutants, including nutrients and, threatening marine ecosystems. Biological treatments are effective but vulnerable to disruptions, especially during typhoons, which alter water quality and microbial communities. This study examined a mariculture tailwater (MTW) treatment system in Hainan over a year, focusing on seasonal performance in nutrient and ARGs removal, microbial community dynamics, impacts of environmental changes on functional microorganisms, and interactions of hosts of antibiotic resistance genes. The system effectively removed NH4+-N (63.74-94.73%) during non-typhoon seasons, but typhoons disrupted its nutrient pollutant reduction performance. The proportion of microorganisms involved in nitrogen and phosphorus removal decreased by changes of salinity in typhoon events. Antibiotic resistance genes relative abundances were enriched due to typhoon disaster. The majority antibiotic resistance genes in the system were associated with beta-lactam resistance (4.37 × 104-8.73 × 104). Rare bacterial taxa showed the strongest tolerance in all taxa to typhoon conditions. Archaeal community compositions were sensitive to these disturbances. Disperal limitation and heterogeneous selection were key drivers in bacterial and archaeal community assemblies. Microorganisms and antibiotic resistance genes often co-occurred in non-typhoon seasons. Vibrio was identified as a key potential host of antibiotic resistance genes in both seasons. This study highlights the disruptive effect of typhoons on the stability of MTW treatment systems.

Recent advances in the biological treatment of wastewater rich in emerging pollutants produced by pharmaceutical industrial discharges

Pharmaceuticals and personal care products present potential risks to human health and the environment. In particular, wastewater treatment plants often detect emerging pollutants that disrupt biological treatment. The activated sludge process is a traditional biological method with a lower capital cost and limited operating requirements than more advanced treatment methods. In addition, the membrane bioreactor combines a membrane module and a bioreactor, widely used as an advanced method for treating pharmaceutical wastewater with good pollution performance. Indeed, the fouling of the membrane remains a major problem in this process. In addition, anaerobic membrane bioreactors can treat complex pharmaceutical waste while recovering energy and producing nutrient-rich wastewater for irrigation. Wastewater characterizations have shown that wastewater's high organic matter content facilitates the selection of low-cost, low-nutrient, low-surface-area, and effective anaerobic methods for drug degradation and reduces pollution. However, to improve the biological treatment, researchers have turned to hybrid processes in which all physical, chemical, and biological treatment methods are integrated to remove various emerging contaminants effectively. Hybrid systems can generate bioenergy, which helps reduce the operating costs of the pharmaceutical waste treatment system. To find the most effective treatment technique for our research, this work lists the different biological treatment techniques cited in the literature, such as activated sludge, membrane bioreactor, anaerobic treatment, and hybrid treatment, combining physicochemical and biological techniques.

Effect of external carbon addition and enrofloxacin on the denitrification and microbial community of sequencing batch membrane reactor treating synthetic mariculture wastewater

The effect of sequencing batch membrane bioreactor (SMBR) on external carbon addition and enrofloxacin was investigated to treat synthetic mariculture wastewater. Anoxic/anaerobic and low COD/TN can improve the ammonia oxidation of the system, and the NH₄⁺-N removal efficiency above 99%. External carbon was added and an anoxic environment was set to provide a suitable environment for denitrifying bacteria. When the external carbon source was 50-207 mg/L, the TN removal efficiency (31.82%-37.73%) and the COD of the effluent (28.85-36.58 mg/L) had little change. The partition resistance model showed that cake deposition resistance (R_C,irr) and irreversible resistance (R_PB) were the main components. And with the increase in cleaning times, the fouling rate of membrane components accelerated. Enrofloxacin can promote the TN removal efficiency (45.66%-93.74%) and had a significant effect on TM7a, Cohaesibacter, Vibrio and Phaeobacter.

Impacts of bio-carriers on the characteristics of cake layer and membrane fouling in a novel hybrid membrane bioreactor for treating mariculture wastewater

Membrane fouling is generally considered as a major bottleneck to the wide application of membrane bioreactor (MBR) for high saline mariculture wastewater treatment. Though numerous researches have investigated the membrane fouling of MBR combined with bio-carriers, few studies reveal the impacts of bio-carriers on the characteristics of cake layer and the mechanism of bio-carriers alleviating membrane fouling. In this study, two systems, namely carriers-enhanced MBR (R1) and conventional MBR (R2) were parallel operated, drawing a conclusion that bio-carriers effectively improved the characteristics of cake layer, thus mitigating membrane fouling. Fluorescence excitation emission matrix (EEM) analysis indicated that bio-carriers reduced the adhesion of proteins and humic acid-like materials on membrane surface. Molecular weight (Mw) distribution suggested that soluble microbial products (SMP) with small Mw (6-20 kDa) and biopolymers in extracellular polymeric substances (EPS) (50-300 kDa) was easier to accumulate on membrane surface in R2. The above results indicated that the presence of bio-carriers could effectively reduce the attachment of these organics on membrane surface, contributing to a larger porosity of cake layer and thus mitigating membrane fouling. Meanwhile, gas chromatography-mass spectrometry (GC-MS) clarified that more components were present in R2 than R1. Moreover, the majority of compounds in the SMP were present in both systems, while only 14 compounds in the EPS were the same between R1 and R2. Noticeably, certain aromatics only existed in R2, suggesting that bio-carriers effectively reduced the accumulation of recalcitrant materials, especially aromatics. These results revealed that bio-carriers shifted the precise composition of cake layers.