Purification of the secondary treatment tail water for wastewater reclamation by integrated subsurface-constructed wetlands.

A whole-year investigation of full-scale integrated subsurface-constructed wetlands (ISCWs) was carried out to purify the tail water from a wastewater treatment plant (WWTP) for wastewater reclamation under four plant species, four hydraulic loading rates (HLRs), and four seasons. The results showed that ISCWs were effective for the purification of WWTP discharge, with the average removal efficiencies of COD, NH4+-N, TN, and TP being 48%, 49%, 9%, and 30%, respectively. Typical pollutant concentrations in the treated effluent of ISCWs were 8.19 mg/L COD, 1.76 mg/L NH4+-N, 11.57 mg/L TN, and 0.36 mg/L TP, which met most of the water quality standards for reusing recycling water. Emergent plants with well-developed root systems may be capable of promoting the decontamination of ISCWs. Seasonal change played an important role in the treatment process: the removal of phosphorus by plant uptake and microbial utilization was more active in the warm season and the co-occurrence of organic degradation and nitrification, whereas the cold season is conducive to exothermic adsorption process of pollutants to substrates. Properly increasing the HLRs may improve the availability of ISCWs according to the requirement of effluent quality. Furthermore, the C/N ratio might be the key factor for the purification effect of ISCWs, because the COD level of WWTP discharge may change the process of NH4+-N biotransformation.

Spatial and Temporal Characteristics of Phytoplankton Communities in Drinking Water Source Reservoirs in Shenzhen, China.

Phytoplankton diversity and community characteristics are closely associated with aquatic environmental factors. Understanding these dynamics can provide insights into the ecological health of water bodies. We investigate the spatial and temporal characteristics of phytoplankton communities in 27 drinking water source reservoirs in Shenzhen, China. As a method, we collected samples during the dry season in 2021 and the wet season in 2022, analyzed the alpha and beta diversities of phytoplankton communities, and correlated these with the environmental factors. The results reveal that Cyanobacteria dominate the phytoplankton communities in the Shenzhen reservoirs. Phytoplankton diversity is greater during the dry season. The algal composition varies spatially, and the phytoplankton diversity tends to decrease with increasing eutrophication. A co-occurrence network analysis indicates denser and stronger correlations among phytoplankton nodes during the wet season than dry season. Reservoirs with moderate eutrophication levels exhibit denser nodes and stronger correlations compared to those with low or high eutrophication levels. The chemical oxygen demand, water temperature, pH, and total nitrogen are identified as key influencers of the phytoplankton community structure. Our results contribute to the enhanced understanding of the spatial and temporal dynamics of phytoplankton communities in reservoirs in South China and provides insights into the management and conservation of these drinking water reservoirs.

A three-year study on the treatment of domestic-industrial mixed wastewater using a full-scale hybrid constructed wetland.

Three full-scale constructed wetlands (CWs), namely vertical flow (VFCW), surface flow (SFCW), and horizontal flow (HFCW) systems, were combined in a series process to form a hybrid CW, which was used for the treatment performance of domestic-industrial mixed wastewater and investigated over a three-year period. The hybrid CW demonstrated that it is effective and stable during the long-term treatment of high-loading mixed wastewater under different operation years, season changes, and technology processes, with the average removal efficiencies of suspended solids, chemical oxygen demand, biological oxygen demand, total nitrogen, ammonia nitrogen, nitrate nitrogen, and total phosphorous being 84, 40, 54, 54, 70, 40, and 46%, respectively. The effluent quality of the hybrid CW reached the highest discharge standard for wastewater treatment plants. First, a variety of pollutants from the mixed wastewater were effectively removed in the subsurface processes (VFCW and HFCW) via substrate adsorption and degradation of the attached biofilm. The higher dissolved oxygen content and oxygen transfer capacity values in the VFCW were favourable for the occurrence of aerobic pathways (such as nitrification and inorganic phosphorus oxidation). In addition, with the large consumption of oxygen in the previous process, the oxygen-enriching capacity of the SFCW processes, provided aerobic potential for the next stage. In particular, the plant debris in the SFCW temporarily increased the organics and suspended solids, further increasing the C/N ratio, which was beneficial for denitrification as the main nitrogen removal pathway in the HFCW.

Optimization of constructed wetlands on purifying black-odorous water and their potential purification mechanism.

Black-odorous water has become a common and widespread problem in recent decades. In this study, nine constructed wetlands (CWs) with different flow types, filters, plants, and hydraulic loadings were designed according to an orthogonal array (L9 (34), and were used for the purification of black-odorous water in summer and winter. The results showed that CWs are regarded as effective to purify black-odorous water in both seasons. Microbial degradation is the major removal pathway of pollutants in CWs during summer, while the joint effect of biodegradation and adsorption is the main treatment route during winter. Flow type and hydraulic loading appear to be the most important factors impacting the purification performance of CWs, by changing the redox condition of systems and retention time of contaminants, respectively. 'Vertical flow-zeolite filter-high loading' is proposed as the best parameter selection for CWs on the purification of black-odorous water: among them, CWs with vertical flow have better oxygen transport capacity that is conductive to aerobic processes of pollutants, zeolite substrates may adsorb more nitrogen via ion exchange, higher hydraulic loadings can extend the contact time between contaminants and filters, and regulate the water temperature for microbial activity.

Adaptive Responses of the Sea Anemone Heteractis crispa to the Interaction of Acidification and Global Warming.

Ocean acidification and warming are two of the most important threats to the existence of marine organisms and are predicted to co-occur in oceans. The present work evaluated the effects of acidification (AC: 24 ± 0.1 °C and 900 µatm CO2), warming (WC: 30 ± 0.1 °C and 450 µatm CO2), and their combination (CC: 30 ± 0.1 °C and 900 µatm CO2) on the sea anemone, Heteractis crispa, from the aspects of photosynthetic apparatus (maximum quantum yield of photosystem II (PS II), chlorophyll level, and Symbiodiniaceae density) and sterol metabolism (cholesterol content and total sterol content). In a 15-day experiment, acidification alone had no apparent effect on the photosynthetic apparatus, but did affect sterol levels. Upregulation of their chlorophyll level is an important strategy for symbionts to adapt to high partial pressure of CO2 (pCO2). However, after warming stress, the benefits of high pCO2 had little effect on stress tolerance in H. crispa. Indeed, thermal stress was the dominant driver of the deteriorating health of H. crispa. Cholesterol and total sterol contents were significantly affected by all three stress conditions, although there was no significant change in the AC group on day 3. Thus, cholesterol or sterol levels could be used as important indicators to evaluate the impact of climate change on cnidarians. Our findings suggest that H. crispa might be relatively insensitive to the impact of ocean acidification, whereas increased temperature in the future ocean might impair viability of H. crispa.

Removal efficiency, kinetic, and behavior of antibiotics from sewage treatment plant effluent in a hybrid constructed wetland and a layered biological filter.

Sewage treatment plant (STP) is the major point source of antibiotic contamination, yet the advanced treatment of antibiotic polluted STP effluent has not been given necessary attention. This study is conducted to evaluate the removal efficiency, kinetic, and behavior of sulfonamides, quinolones, tetracyclines, and macrolides antibiotics from STP effluent in a hybrid constructed wetland (HCW) and a layered biological filter (LBF) at different hydraulic loading rates (HLRs). The results showed that the removal efficiency of antibiotics in all the HLRs was ranked as follow: quinolones of HCW (70-95%) > macrolides of HCW (58-77%) > tetracyclines of both systems (59-67%) > quinolones of LBF (28-64%) > macrolides of LBF (13-25%) > sulfonamides of both systems (<0%). The optimal HLR is 1.0 m/day for quinolones and 2.0 m/day for tetracyclines-macrolides in the HCW, and 6.4 m/day for quinolones-tetracyclines in the LBF, respectively. Although HCW performed better on the removal of most antibiotics, LBF exhibited stronger total loading toleration and higher removal loading ability to antibiotics. Among them, quinolones were markedly removed by multiple effect of substrate adsorption, microbial anaerobic degradation, and photolysis in the HCW (planted), and by filter sorption and interception in the LBF (unplanted); adsorption is the dominant elimination approach for tetracyclines in both systems; plant uptake plays a significant role on the removal of macrolides in the HCW.

Exhaled carbon monoxide and its associations with smoking, indoor household air pollution and chronic respiratory diseases among 512,000 Chinese adults.

BACKGROUND: Exhaled carbon monoxide (COex) level is positively associated with tobacco smoking and exposure to smoke from biomass/coal burning. Relatively little is known about its determinants in China despite the population having a high prevalence of smoking and use of biomass/coal. METHODS: The China Kadoorie Biobank includes 512,000 participants aged 30-79 years recruited from 10 diverse regions. We used linear regression and logistic regression methods to assess the associations of COex level with smoking, exposures to indoor household air pollution and prevalent chronic respiratory conditions among never smokers, both overall and by seasons, regions and smoking status. RESULTS: The overall COex level (ppm) was much higher in current smokers than in never smokers (men: 11.5 vs 3.7; women: 9.3 vs 3.2). Among current smokers, it was higher among those who smoked more and inhaled more deeply. Among never smokers, mean COex was positively associated with levels of exposures to passive smoking and to biomass/coal burning, especially in rural areas and during winter. The odds ratios (OR) and 95% confidence interval (CI) of air flow obstruction (FEV1/FVC ratio<0.7) for never smokers with COex at 7-14 and ≥14 ppm, compared with those having COex<7, were 1.38 (1.31-1.45) and 1.65 (1.52-1.80), respectively (Ptrend<0.001). Prevalence of other self-reported chronic respiratory conditions was also higher among people with elevated COex (P<0.05). CONCLUSION: In adult Chinese, COex can be used as a biomarker for assessing current smoking and overall exposure to indoor household air pollution in combination with questionnaires.

Removal and factors influencing removal of sulfonamides and trimethoprim from domestic sewage in constructed wetlands.

Twelve pilot-scale constructed wetlands with different configurations were set up in the field to evaluate the removal and factors that influence removal of sulfonamides (sulfadiazine, sulfapyridine, sulfacetamide, sulfamethazine and sulfamethoxazole) and trimethoprim from domestic sewage. The treatments included four flow types, three substrates, two plants and three hydraulic loading rates across two seasons (summer and winter). Most target antibiotics were efficiently removed by specific constructed wetlands; in particular, all types of constructed wetlands performed well for the degradation of sulfapyridine. Flow types were the most important influencing factor in this study, and the best removal of sulfonamides was achieved in vertical subsurface-flow constructed wetlands; however, the opposite phenomenon was found with trimethoprim. Significant relationships were observed between antibiotic degradation and higher temperature and redox potential, which indicated that microbiological pathways were the most probable degradation route for sulfonamides and trimethoprim in constructed wetlands.