Qiaoying Wang

Microsieving-based advanced primary treatment (APT) has attracted increasing attention as an approach for restructuring carbon and energy flows within wastewater treatment plants (WWTPs). Unlike previous work that has often addressed individual microsieving technologies or specific recovery routes separately, this review provides a unified framework for comparing drum screens (DSs)/drum filters (DFs), cloth disc filters (CDFs), and rotating belt filters (RBFs) with conventional primary sedimentation (PST) in terms of separation mechanisms and pollutant capture. On this basis, it further discusses recent progress in energy and resource recovery from primary screenings, together with their relevance to energy demand reduction and carbon redistribution in WWTPs. Current limitations arise at two levels. Microsieving technologies remain constrained by mesh fouling and limited control over selective pollutant capture, while plant-wide evidence remains insufficient, particularly regarding techno-economic assessment of recovered products and life cycle assessment of full plant performance after replacing primary sedimentation. Future work should therefore focus on targeted process optimization and plant-wide evaluation of economic and environmental feasibility.

The demand for lithium (Li) is rapidly growing as Li-ion batteries play an increasingly important role in achieving the global "net-zero emissions". Direct lithium extraction (DLE) technologies have emerged as a transformative technology for efficiently and sustainably producing Li products from brine. While numerous studies have focused on improving Li⁺/Mg²⁺ selectivity, proper Li⁺ concentration before carbonation is largely overlooked. In this critical review, we examine the critical performance requirements for DLE, focusing on active-control DLE technologies where external fields actively regulate extraction, including nanofiltration, electrodialysis, and electrosorption. Although all three technologies can achieve high Li⁺/Mg²⁺ selectivity with the development of advanced materials, electrodialysis and electrosorption are capable of simultaneously separating and concentrating Li⁺, making them more promising for realizing a real DLE process compared to nanofiltration. Furthermore, we compare the economic and environmental performance of these technologies. While the levelized cost of lithium carbonate for electrosorption (5,400 USD ton^-1) is comparable to nanofiltration and electrodialysis, its global warming potential (-3911 kg CO₂ eq) is markedly lower. Thus, electrosorption theoretically emerges as the most promising candidate for achieving a truly environmentally sustainable DLE process. Finally, we discuss the key challenges to industrial deployment of ES and outline potential strategies for their resolution.

Although adding iron salts can improve phosphorus removal in membrane bioreactor (MBR) processes, overdosing iron salts may result in excessive iron concentrations in the effluent and pose risks of surface water contamination. In this study, an optimized iron salt dosing method was proposed to comprehensively investigate its effects on the performance of MBRs and the control of iron leakage. The results showed that batch dosing of solid iron salts (Fe₂(SO₄)₃) into the influent or activated sludge maintained an effluent Fe³⁺ concentration below 1.0 mg/L and a total phosphorus (TP) concentration below 0.30 mg/L. Long-term operation of the MBR (under conditions of HRT = 4.3 h, SRT = 20 d, and MLSS = 12 g/L) showed that batch dosing of solid iron salts led to an increase in the effluent ammonia–nitrogen (NH₃-N) concentration, and the nitrification effect was restored after supplementing the alkalinity. Iron salts increased the TP removal rate by approximately 40% while inhibiting the biological phosphorus removal capacity. The average Fe³⁺ concentration in the membrane effluent (0.23 ± 0.11 mg/L) met China’s Environmental Quality Standard for Surface Water (GB3838-2002). This study demonstrates that batch dosing of solid iron salts effectively controls iron concentration in the MBR effluent while preventing secondary pollution. The mechanisms of the impact of iron salts on MBR performance provide crucial theoretical and technical support for MBR process optimization.

Solid waste governance is a significant global challenge, particularly exacerbated in rapidly urbanizing, low- income countries that often lack the infrastructure and resources to manage increasing waste volumes. This study investigates the challenges and practices of integrated solid waste management (ISWM) in Menelik Sub-City, Debre Berhan, Ethiopia. This study utilized both qualitative and quantitative methods, including household surveys, key informant interviews, direct observation, and focus group discussions. A systematic random sampling technique was used to select respondents from residents, cooperative partnership associations, and sanitation administration staff. The results indicated that 37.4% of respondents recognized the lack of skilled manpower as a significant contributor to the inefficiency of solid waste management (SWM) while 40.3% of respondents highly agreed that inadequate infrastructure hindered the efficiency of SWM systems in the study area. The findings showed limited waste management practices in study area have environmental challenges and public health impacts. This is mainly due to inadequate waste collection, transportation, and disposal systems. Moreover, Menelik sub-city had to face tremendous challenges in waste management in the recent past, due to a number of factors–its growing population, increasing complexity of waste streams, and lack of effective waste management systems, proper infrastructure, capital investment, financial and human resources, as well as effective policy and regulatory enforcement. This study offers critical data and analysis that can inform policymakers, urban planners, and researchers. By identifying key barriers and effective practices, the findings contribute to the broader scientific discourse on sustainable waste management, particularly in rapidly urbanizing regions of developing countries. The findings highlighted an integrated solid waste management (ISWM) based on the 5Rs (i.e. refuse, reduction, reuse, recycle and recovery) approach is an environmentally sustainable and socially acceptable solution, which urgently needed to be implemented by the city.

Biological foaming is a major problem in activated sludge (AS) wastewater treatment systems. In this study, four wastewater treatment plants (WWTPs) (a total of six AS treatment systems) were investigated. The microscopic examination shows that foaming was mainly caused by gram-positive short branch microorganisms, sludge fragments, and/or other microorganisms, while the long unbranched filamentous was easy to cause bulking. The high throughput sequencing (HTS) and Linear discriminant analysis effect Size (LEfSe) identified the significant discrepancy of bacteria in foams compared to normal AS. Mycobacterium, Mycobacteriaceae, Nocardiaceae, Actinomycetales, Chryseobacterium, Flavobacterium, Ormithobacterium, Flavobacteriaceae, and Portibacter were considered as the dominant foaming-potential bacteria but not the most abundant bacteria in the foams. The excessive growth of foaming bacteria (including Haliscomentbacter, Saprospiraceae, and Tetrasphra) directly led to bulking with a high sludge volume index and was positively correlated with sludge retention time (SRT) and negatively correlated with dissolved oxygen (DO), which means long SRT and low DO may lead bulking instead of foaming. It also found that the foaming bacteria (including Skermania, Comamonadaceae, Cloacibacterium, Flavobacterium, and Chryseobacterium) had significant positive correlations with suspended solids and mixed liquid suspended solids, and negative correlations with temperature and DO concentration.