Performance and membrane fouling of two types of laboratory-scale submerged membrane bioreactors for hospital wastewater treatment at low flux condition

© 2016 Elsevier B.V. All rights reserved. The performance and membrane fouling of a lab-scale submerged sponge-membrane bioreactor (Sponge-MBR) and a conventional MBR were investigated and compared for hospital wastewater treatment at low fluxes of 2-6 LMH. COD removal by the Sponge-MBR was similar to that of the MBR, while the Sponge-MBR achieved 9-16% removed more total nitrogen than the MBR. This was due to 60% of total biomass being entrapped in the sponges, which enhanced simultaneous nitrification denitrification. Additionally, the fouling rates of the Sponge-MBR were 11-, 6.2- and 3.8-times less than those of the MBR at flux rates of 2, 4 and 6 LMH, respectively. It indicates the addition of sponge media into a MBR could effectively reduce the fouling caused by cake formation and absorption of soluble substances in a low flux scenario

Wastewater treatment and biomass growth of eight plants for shallow bed wetland roofs

© 2017 Elsevier Ltd Wetland roof (WR) could bring many advantages for tropical cities such as thermal benefits, flood control, green coverage and domestic wastewater treatment. This study investigates wastewater treatment and biomass growth of eight local plants in shallow bed WRs. Results showed that removal rates of WRs were 21–28 kg COD ha−1 day−1, 9–13 kg TN ha−1 day−1 and 0.5–0.9 kg TP ha−1 day−1, respectively. The plants generated more biomass at lower hydraulic loading rate (HLR). Dry biomass growth was 0.4–28.1 g day−1 for average HLR of 247–403 m3 ha−1 day−1. Green leaf area of the plants was ranging as high as 67–99 m2 leaves per m2 of WR. In general, the descent order of Kyllinga brevifoliaRottb (WR8), Cyperus javanicus Houtt (WR5) and Imperata cylindrical (WR4) was suggested as effective vegetations in WR conditions in terms of wastewater treatment, dry biomass growth and green coverage ratio

Aerobic co-composting degradation of highly PCDD/F-contaminated field soil. A study of bacterial community

© 2018 Elsevier B.V. This study investigated bacterial communities during aerobic food waste co-composting degradation of highly PCDD/F-contaminated field soil. The total initial toxic equivalent quantity (TEQ) of the soil was 16,004 ng-TEQ kg −1 dry weight. After 42-day composting and bioactivity-enhanced monitored natural attenuation (MNA), the final compost product's TEQ reduced to 1916 ng-TEQ kg −1 dry weight (approximately 75% degradation) with a degradation rate of 136.33 ng-TEQ kg −1 day −1 . Variations in bacterial communities and PCDD/F degraders were identified by next-generation sequencing (NGS). Thermophilic conditions of the co-composting process resulted in fewer observed bacteria and PCDD/F concentrations. Numerous organic compound degraders were identified by NGS, supporting the conclusion that PCDD/Fs were degraded during food waste co-composting. Bacterial communities of the composting process were defined by four phyla (Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes). At the genus level, Bacillus (Firmicutes) emerged as the most dominant phylotype. Further studies on specific roles of these bacterial strains are needed, especially for the thermophiles which contributed to the high degradation rate of the co-co-composting treatment's first 14 days

White hard clam (Meretrix lyrata) shells media to improve phosphorus removal in lab-scale horizontal sub-surface flow constructed wetlands: Performance, removal pathways, and lifespan.

This work examined the phosphorus (P) removal from the synthetic pretreated swine wastewater using lab-scale horizontal sub-surface flow constructed wetlands (HSSF-CWs). White hard clam (Meretrix lyrata) shells (WHC) and Paspalum atratum were utilized as substrate and plant, respectively. The focus was placed on treatment performance, removal mechanisms and lifespan of the HSSF-CWs. Results indicated that WHC-based HSSF-CW with P. atratum exhibited a high P removal (89.9%). The mean P efluent concentration and P removal rate were 1.34 ± 0.95 mg/L and 0.32 ± 0.03 g/m2/d, respectively. The mass balance study showed that media sorption was the dominant P removal pathway (77.5%), followed by microbial assimilation (14.5%), plant uptake (5.4%), and other processes (2.6%). It was estimated the WHC-based bed could work effectively for approximately 2.84 years. This WHC-based HSSF-CWs technology will therefore pave the way for recycling Ca-rich waste materials as media in HSSF-CWs to enhance P-rich wastewater purification

The Individual and Synergistic Indexes for Assessments of Heavy Metal Contamination in Global Rivers and Risk: a Review

This article provides an overview of heavy metal contamination in rivers and assessment methods of their contamination and effects. According to literature, rivers with heavy metal contamination in surface water are mainly found in developing countries in Asia, Africa, and Latin America and the Caribbean area, while rivers with heavy metal contamination in sediments are mostly found in Europe. The increase in heavy metal contamination in rivers has led to the adoption of individual and synergistic assessment methods. Individual methods are useful in assessing the contamination and effects for a single heavy metal, while synergistic methods assess the combined contamination and effects of several heavy metals present in surface water and sediments. These two approaches have been commonly used together in recent studies to overcome the limitations of each other and provide a more comprehensive assessment. The developments, equations, advantages, limitations, and future perspectives of these methods are discussed in this review. Calculating indexes are simple, easy-to-implement, and effective methods to provide early alerts for the environmental changes and the adverse impacts on ecosystems and human health. However, calculating indexes still have limitations due to the lack of background concentrations of heavy metals in the study area. Therefore, this issue should be addressed to overcome the limitations of these methods in the future. This review provides a useful reference for future studies on heavy metal contamination in global rivers and the assessment methods for heavy metal contamination and effects

Nitrogen removal in subsurface constructed wetland: Assessment of the influence and prediction by data mining and machine learning

Subsurface constructed wetland (SCW) appears to be an economical and environmental-friendly practice to treat nitrogen-enriched (waste) water. Nevertheless, the removal mechanisms in SCW are complicated and rather time-consuming to conduct and assessment the efficiency of new experiments. This work mined data from literature and developed the machine learning models to elucidate the effect of influent inputs and predict ammonium removal rate (ARR) in SCW treatment. 755 sets and 11 attributes were applied in four modeled algorithms, including Random forest, Cubist, Support vector machines, and K-nearest neighbors. Six out of ten input features including ammonium (NH4), total nitrogen (TN), hydraulic loading rate (HLR), the filter height (i.e., Height), aeration mode (i.e., Aeration), and types of inlet feeding (i.e., Feeding) have posed pronounced influences on the ARR. The Cubist algorithm appears the most optimal model showing the lowest RMSE i.e., 0.974 and the highest R2 i.e., 0.957. The contribution of variables followed the order of NH4, HLR, TN, Aeration, Height and Feeding corresponding to 97, 93, 71, 49, 34, and 34%, respectively. The generalization ability to forecast ARR using testing data achieved the R2 of 0.970 and the RMSE of 1.140 g/m2 d, indicating that Cubist is a reliable tool for ARR prediction. User interface and web tool of final predictive model are provided to facilitate the application for designing and developing SCW system in real practice

A mini-review on shallow-bed constructed wetlands: a promising innovative green roof

© 2019 Elsevier B.V. Shallow-bed constructed wetland (SCW) has been used as a secondary wastewater treatment technology with low cost, less maintaining, and operational requirements and environmental friendliness. Green roof has been considered an effective solution in saving energy, enhancing green space, providing landscape aesthetics, limiting stormwater runoff causing flooding, and purifying air pollutants. Recently, a wetland roof (WR) has been interested as a good integration of these two technologies. To gain an insight understanding of this combination, this review aimed to provide the potential applications of SCW on the roof as a WR. Factors affecting performance, benefits, and challenges of SCW were also discussed. The literature data showed WR was a promising green technology that is needed to be investigated and scaled up in the future