Comparison and modeling of two biofilm processes applied to decentralized wastewater treatment

In order to control water pollution in the rapidly urbanizing South China area,biological contact oxidation(BCO)process and biological aerated filter(BAF)process were applied in a pilot-scale experiment for decentralized wastewater treatment.An investigation to find the optimal parameters of the two biofilm systems was conducted on hydraulic loading,organic loading,and aeration rate.The results indicated that the water reuse criteria required a maximum hydraulic and organic loading of 30.0 m^(3)/(m^(2)·d)and 4.0 kg COD/(m^(3)·d),respectively,as well as a minimum effluent DO of 4.0 mg/L.The utilization of a new media allowed BAF to perform better than BCO.The kinetic description of the COD removal process for BAF and BCO are Se=S0e^(-0.639t)/(1+1.035t),and S_(e)=S_(0)/[(1+0.947t)(1+1.242t)],respectively.The correlativity analysis showed that the two models could predict the effluent water quality based on the hydraulic retention time.Thus,the appropriate hydraulic loading for certain effluent water quality demands could be determined.The two models could be applied to wastewater treatment practice.

Distribution of antibiotic resistance genes and their association with bacteria and viruses in decentralized sewage treatment facilities

The distribution of antibiotic resistance genes(ARGs)has been intensively studied in large-scale wastewater treatment plants and livestock sources.However,small-scale decentralized sewage treatment facilities must also be explored due to their possible direct exposure to residents.In this study,six wastewater treatment facilities in developed rural areas in eastern China were investigated to understand their risks of spreading ARGs.Using metagenomics and network analysis tools,ARGs and bacterial and viral communities were identified in the influent(INF)and effluent(EFF)samples.The dominant ARGs belonged to the bacitracin class,which are different from most of municipal wastewater treatment plants(WWTPs).The dominant hosts of ARGs are Acidovorax in bacterial communities and Prymnesiovirus in viral communities.Furthermore,a positive relationship was found between ARGs and phages.The ARGs significantly correlated with phages were all hosted by specific genera of bacteria,indicating that phages had contributed to the ARG’s proliferation in sewage treatment facilities.Paying significant concern on the possible enhanced risks caused by bacteria,viruses and their related ARGs in decentralized sewage treatment facilities is necessary.

Hybrid energy harvesting systems for self-powered sustainable water purification by harnessing ambient energy

The development of self-powered water purification technologies for decentralized applications is crucial for ensuring the provision of drinking water in resource-limited regions. The elimination of the dependence on external energy inputs and the attainment of self-powered status significantly expands the applicability of the treatment system in real-world scenarios. Hybrid energy harvesters, which convert multiple ambient energies simultaneously, show the potential to drive self-powered water purification facilities under fluctuating actual conditions. Here, we propose recent advancements in hybrid energy systems that simultaneously harvest various ambient energies (e.g., photo irradiation, flow kinetic, thermal, and vibration) to drive water purification processes. The mechanisms of various energy harvesters and point-of-use water purification treatments are first outlined. Then we summarize the hybrid energy harvesters that can drive water purification treatment. These hybrid energy harvesters are based on the mechanisms of mechanical and photovoltaic, mechanical and thermal, and thermal and photovoltaic effects. This review provides a comprehensive understanding of the potential for advancing beyond the current state-of-the-art of hybrid energy harvester-driven water treatment processes. Future endeavors should focus on improving catalyst efficiency and developing sustainable hybrid energy harvesters to drive self-powered treatments under unstable conditions (e.g., fluctuating temperatures and humidity).

Greywater reuse as a key enabler for improving urban wastewater management

Sustainable water management is essential to guaranteeing access to safe water and addressing the challenges posed by climate change,urbanization,and population growth.In a typical household,greywater,which includes everything but toilet waste,constitutes 50e80%of daily wastewater generation and is characterized by low organic strength and high volume.This can be an issue for large urban wastewater treatment plants designed for high-strength operations.Segregation of greywater at the source for decentralized wastewater treatment is therefore necessary for its proper management using separate treatment strategies.Greywater reuse may thus lead to increased resilience and adaptability of local water systems,reduction in transport costs,and achievement of fit-for-purpose reuse.After covering greywater characteristics,we present an overview of existing and upcoming technologies for greywater treatment.Biological treatment technologies,such as nature-based technologies,biofilm technologies,and membrane bioreactors(MBR),conjugate with physicochemical treatment methods,such as membrane filtration,sorption and ion exchange technologies,and ultraviolet(UV)disinfection,may be able to produce treated water within the allowable parameters for reuse.We also provide a novel way to tackle challenges like the demographic variance of greywater quality,lack of a legal framework for greywater management,monitoring and control systems,and the consumer perspective on greywater reuse.Finally,benefits,such as the potential water and energy savings and sustainable future of greywater reuse in an urban context,are discussed.