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The multi-soil-layering (MSL) systems is an emerging solution for environmentally-friendly and cost-effective treatment of decentralized rural domestic wastewater. However, the role of the seemingly simple permeable layer has been overlooked, potentially holding the breakthroughs or directions to addressing suboptimal nitrogen removal performance in MSL systems. In this paper, the mechanism among diverse substrates (zeolite, green zeolite and biological ceramsite) coupled microorganisms in different systems (activated bacterial powder and activated sludge) for rural domestic wastewater purification was investigated. The removal efficiencies performed by zeolite coupled with microorganisms within 3 days were 93.8% for COD, 97.1% for TP, and 98.8% for NH 4 +-N. Notably, activated sludge showed better nitrification and comprehensive performance than specialized nitrifying bacteria powder. Zeolite attained an impressive 89.4% NH 4 +-N desorption efficiency, with a substantive fraction of NH 4 +-N manifesting as exchanged ammonium. High-throughput 16S rRNA gene sequencing revealed that aerobic and parthenogenetic anaerobic bacteria dominated the reactor, with anaerobic bacteria conspicuously absent. And the heterotrophic nitrification-aerobic denitrification (HN-AD) process was significant, with the presence of denitrifying phosphorus-accumulating organisms (DPAOs) for simultaneous nitrogen and phosphorus removal. This study not only raises awareness about the importance of the permeable layer and enhances comprehension of the HN-AD mechanism in MSL systems, but also provides valuable insights for optimizing MSL system construction, operation, and rural domestic wastewater treatment. [ABSTRACT FROM AUTHOR]

Rural domestic sewage has become very serious, while only 17.4% of it is treated centrally or partially, which results in environmental pollution and waste of water resources. To solve this problem, a wastewater treatment system by modular coupling is proposed, and the processing module includes two or three of multi-stage ecological pond, multi-stage drop aeration ecological ditch and multi-stage drop dam. The analysis of three examples shows that the system has a good treatment effect on chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4 +-N) and total phosphorus (TP), and the removal ratios are 90.22%, 82.07%, 91.60%, 81.48%, respectively, when the flow rate is 3 m3/h. After 28 days of continuous operation, the treatment capacity decreases by about 10%, indicating that the system has good long-term treatment performance. The removal ratio decreases slightly under different flow rates, which shows its great adaptability in different hydraulic conditions. In practical application, the system can select different coupling systems according to rural terrain and wastewater quality, and it is suitable for the treatment of rural domestic sewage and agricultural non-point source sewage and the repairment of urban sewage and lake eutrophic water body. [ABSTRACT FROM AUTHOR]

Subsurface wastewater infiltration system (SWIS) has been widely used in rural decentralized sewage treatment due to its low cost, low energy consumption, high efficiency, and other advantages. Numerous researches have reported optimizing the SWIS nitrogen removal process, while the relevant mechanisms and optimization methods have not been well summarized. As such, this review aims to fill the above gaps as follows. Firstly, the SWIS nitrogen removal efficiency and mechanism are outlined, and the role of microorganisms is described in detail. Moreover, the issue of N2O emission in nitrogen removal was introduced. Secondly, the usage of different types of fillers in substrate improvement was summarized, highlighting the unique advantages of plants used in SWIS. A clear adjustment range and control method is proposed for system operating parameters such as hydraulic loading rate (HLR), organic loading rate (OLR), carbon-nitrogen ratio (CNR), temperature and dissolved oxygen (DO). Finally, the role of bioaugmentation in nitrogen removal was summarized. The part of conclusion and prospects evaluates the development and application of SWIS in rural areas. [ABSTRACT FROM AUTHOR]

Subsurface wastewater infiltration system (SWIS) has been widely used in rural decentralized sewage treatment due to its low cost, low energy consumption, high efficiency, and other advantages. Numerous researches have reported optimizing the SWIS nitrogen removal process, while the relevant mechanisms and optimization methods have not been well summarized. As such, this review aims to fill the above gaps as follows. Firstly, the SWIS nitrogen removal efficiency and mechanism are outlined, and the role of microorganisms is described in detail. Moreover, the issue of N 2 O emission in nitrogen removal was introduced. Secondly, the usage of different types of fillers in substrate improvement was summarized, highlighting the unique advantages of plants used in SWIS. A clear adjustment range and control method is proposed for system operating parameters such as hydraulic loading rate (HLR), organic loading rate (OLR), carbon-nitrogen ratio (CNR), temperature and dissolved oxygen (DO). Finally, the role of bioaugmentation in nitrogen removal was summarized. The part of conclusion and prospects evaluates the development and application of SWIS in rural areas. [Display omitted] [ABSTRACT FROM AUTHOR]

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This paper aims to improve the treatment effect of the multi-soil-layering system (MSL) on rural domestic wastewater. For this, sludge-based biochar materials were selected in the experiments to study its impacts on the treatment of rural domestic wastewater using the MSL. The comparative experiments were conducted for the three MSL systems filled with different materials: the sludge-based biochar (a), wood chips (b), and charcoal (c). The results showed that when the sludge-based biochar material was used as a filler, the removal effect of COD, NH4+-N, TN, TP is better than that of wood chips and charcoal, and the removal rates were 80%, 90%, 65% and 92%, respectively, meeting the Grade A standard specified in the Hebei Province Rural Domestic wastewater Discharge Standard (DB13/2171-2015); hydraulic loading rates (HLRs) have a great impact on the removal of pollutants, and the pollutant indicators in the system (a)re affected by the HLRs in different degrees, i.e., NH4+-N>TP>COD>TN from high to low; considering the treatment efficiency and pollutant removal effect, the HLRs should be selected between 800L/(m²·d) and 1200L/(m²·d). It's concluded finally that the sludge-based biochar material can strengthen the removal effect of the MSL system. This study is of theoretical value for the further research on MSL system and resource utilization of the sludge. [ABSTRACT FROM AUTHOR]

The scarcity of carbon sources presents a significant challenge for the bio-treatment of rural domestic wastewater (RDW). This paper presented an innovative approach to address this issue by investigating the supplementary carbon source through in-situ degradation of particulate organic matter (POM) facilitated by ferric sulfate modified sludge-based biochar (SBC). To prepare SBC, five different contents of ferric sulfate (0%, 10%, 20%, 25%, and 33.3%) were added to sewage sludge. The results revealed that the pore and surface of SBC were enhanced, providing active sites and functional groups to accelerate the biodegradation of protein and polysaccharide. During the 8-day hydrolysis period, the concentration of soluble chemical oxidation demand (SCOD) increased and peaked (1087–1156 mg L−1) on the fourth day. The C/N ratio increased from 3.50 (control) to 5.39 (25% ferric sulfate). POM was degraded the five dominant phyla, which were Actinobacteriota , Firmicutes , Synergistota , Proteobacteria , and Bacteroidetes. Although the relative abundance of dominant phyla changed, the metabolic pathway remained unchanged. The leachate of SBC (<20% ferric sulfate) was beneficial for microbes, but an excessive amount of ferric sulfate (33.3% ferric sulfate) could have inhibition effects on bacteria. In conclusion, ferric sulfate modified SBC holds the potential for the carbon degradation of POM in RDW, and further improvements should be made in future studies. [Display omitted] • Ferric sulfate increased SBC's surface area and active sites. • Ferric sulfate modified SBC promoting POM degradation. • Ferric sulfate modified SBC enriched microbial diversity. • Ferric sulfate modified SBC was friendly for the environment. [ABSTRACT FROM AUTHOR]

Vegetated drainage ditches (eco-ditches) have drawn much attention in recent years for the ability to remediate diffuse contaminants in rural wastewater through sediment retention, plant uptake and interception, and microbial metabolic activities. However, the effect of plant species on microbial community structure and nitrogen (N) retention in ditch sediment remains poorly understood. In this study, mesocosm plastic drums were planted with eight plant species commonly found in ditches and nurtured with wastewater for 150 days. Sediment total nitrogen (TN) was greatly increased after 150-day nurturing with rural wastewater, from 296.03 mg∙kg−1 (Iris japonica Thunb) to 607.88 mg∙kg−1 (Acorus gramineusO). This study also presents the effect of different plant species on sediment microbial communities, thus providing insight into N removal mechanisms in eco-ditch. Fifty-eight differentially abundant taxa were identified, and sediment microbial community structure for no plant (CK), Acg, Canna indica (Cai), and Typha latifolia L. (Tyl) was primarily linked to sediment NH4+-N and TN. Extremely small proportions of ammonia oxidizing bacteria (AOB) and nitrifying bacteria were detected for all treatments, but large proportions of Crenarchaeota, which comprises the widely existent ammonium oxidized archaea (AOA), were found in CK, Acg and Cai. The abundance of Nitrosotalea from Crenarchaeota presented positive correlations with sediment NH4+-N contents and ammonia oxidation function predicted by Faprotax, indicating Nitrosotalea might be the dominant ammonium-oxidizing microbes in sediment samples. The probable NH4+-N removal pathway in wastewater sediment was through a combined effect of AOA, nitrifying bacteria, and anammox.

Great attention has been paid to the potential of wastewater irrigation as a sustainable water source, particularly due to water scarcity and water pollution issues. However, few studies have focused on its adverse effects and on the health risks it may pose. In this study, the physicochemical properties of soils and plants irrigated with rural domestic wastewater and associated microbiological risks were investigated. The results showed that sewage irrigation could increase the production of vegetables and improve soil fertility. While the nitrate content of plants increased significantly, pathogens on plants and in soils increased after irrigation with raw wastewater. In particular, there was a wide range of pathogenic bacteria in the phyllosphere, which may indicate risks if contaminated vegetables are consumed directly. Treated wastewater irrigation was not significantly different from controls, which were irrigated by tap water; consequently, it can be used as an alternative water resource for agricultural irrigation. The presence of a wide spectrum pathogens in wastewater shows the necessity of long-term monitoring and further evaluation.

Reclamation of domestic wastewater for agricultural irrigation is viewed as a sustainable option to create an alternative water source and address water scarcity. Free-living amoebae (FLA), which are amphizoic protozoa, are widely distributed in various environmental sources. The FLA could cause considerable environmental and health risks. However, little information is available on the risk of these protozoa. In this study, we evaluated the feasibility using rural domestic wastewater for agricultural irrigation, and analyzed dynamic changes of the microbial community structure and FLA populations in raw and treated wastewater, as well as the phyllosphere and rhizosphere of lettuce production sites that were irrigated with different water sources. The bacterial community dynamics were analyzed by terminal restriction fragment length polymorphism (T-RFLP). The bacterial community structures in the influent were similar to that in the effluent, while in some cases relative abundances varied significantly. The populations of Acanthamoeba spp. and Hartmannella vermiformis in the anaerobically treated wastewater were significantly higher than in the raw wastewater. The vegetables could harbor diverse amoebae, and the abundances of Acanthamoeba spp. and H. vermiformis in the rhizosphere were significantly higher than in the phyllosphere. Accordingly, our studies show insight into the distribution and dissemination of amoebae in wastewater treatment and irrigation practices. [ABSTRACT FROM AUTHOR]

This paper investigates the removal efficiency of organic matter, nitrogen, phosphorus, coliforms and pathogens from rural domestic wastewater in a two-stage vertical flow multi-soil-layering (MSL) system. The effects of wastewater quality, season and arid climate conditions on pollutants removal efficiency by the system were examined for one year. The experimental setup included two similar MSL systems composed of two layers: soil-mixture-layers (SML) and gravel permeable layers (PL) that are arranged in a brick like pattern. The applied hydraulic loading rate was 1000Lm-2day-1. Results showed that most of the physicochemical contaminants elimination occurred while the wastewater percolated through the first MSL stage. The second stage demonstrated an improvement in the reduction of all pollutants, especially fecal bacteria indicators and pathogens. The mean overall removal rates performed by the two-stage MSL system were 97% for TSS, 96% for BOD5, 91% for COD, 96% for TN and 95% for TP. For bacterial indicators, the combination of two-stage MSL system achieved high log removals between 2.21 and 3.15 log units. Contaminants reduction processes in MSL technology are more dependent on internal than external environmental factors. The effectiveness of the two-stage MSL system to treat domestic wastewater was strongly influenced by wastewater quality. Significant relationships between influent contaminants level and their removal efficiency were found. The efficiency of MSL technology to reduce contaminants is not sensitive to season and air temperature fluctuations. This is due to the capacity of MSL system materials to withstand the air temperature variation, which highlights one of the advantages of MSL's technology. Wastewater quality is the most important factor affecting the removal of contaminants in the MSL, which could be a critical parameter to considered when designing MSL system. Two-stage MSL system achieved a high treated wastewater quality amenable for treated wastewater reuse in agriculture recommended by Moroccan code of practice. Therefore, the combination of two-stage vertical flow MSL system could be considered an efficient and promising domestic wastewater treatment solution in arid countries to promote environmental protection and wastewater reuse. [ABSTRACT FROM AUTHOR]

Phosphorus is an important element that causes water pollution. Artificial wetlands can efficiently dispose phosphorus in domestic sewage. The removal efficiency of phosphorus in domestic sewage and migration characteristics of phosphorus m the system were studied using waste brick artificial wetland. Results were compared between artificial wetland constructed using rural waste red clay brick and a conventional gravel artificial wetland system. Results show that the adsorption intensity of phosphorus by waste bricks was stronger than that of conventional gravel. The removal of phosphorus from waste brick artificial wetland and gravel artificial wetland mainly depended on the adsorption and sedimentation of the filler matrix. The contribution to phosphorus removal by waste brick artificial wetland and gravel artificial wetland was 90.36% and 87.36%, respectively. The adsorption of phosphorus by the filler decreased with rising depth, and the adsorption of phosphorus mainly occurred at 0-40 cm Plant absorption played a minor role, and the contribution rates of phosphorus removal by waste brick artificial wetland and gravel artificial wetland were 9.64% and 12.5%. respectively. The accumulation of phosphorus in the two systems was mainly concentrated on the ground, and the accumulation of total phosphorus was more than 80% of the total amount. The order of total phosphorus in different plant parts was leaf> stem> root. Waste brick artificial system of sewage phosphorus reached the discharge standards of municipal sewage treatment plant pollutant (GB18918-2002) level A standard). Rural waste clay red brick should be selected as a new filler to build an artificial wetland system that deals with rural sewage. [ABSTRACT FROM AUTHOR]

With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time (HRT), temperature, and effluent recycling on the treatment efficiency of an anaerobic filter (AF) reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18°C, 21°C, and 24°C, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67°C, 30.57°C, and 26.91°C; and three effluent recycling ratios of 1:1, 1:2, and 2:1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for NH4+-N , 19% to 23% for NO3−-N, and 12% to 22% for TP. In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for NH4+-N, 30% to 34% for NO3−-N, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30°C, and an effluent recycling ratio of 2:1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.

Fluoroquinolones (FQs) are new environmental pollutants in rural domestic wastewater and vertical flow constructed wetlands (VFCWs) are widely used to treat rural domestic wastewater. However, studies on degradation products of FQs by VFCWs and ecological risks assessment have been very limited so far. The degradation of FQs by VFCWs under different hydraulic loads was investigated in this study. The results showed all VFCWs had high removal efficiencies of FQs under either high hydraulic load (above 80%) or low hydraulic load (above 95%). Only one degradation product of FQs was detected and the ecotoxicity declined significantly under low hydraulic load. Six degradation products of FQs were detected and the ecotoxicity had also been reduced in general under high hydraulic load. Cytochrome P450 and enzymes with acetyl transfer activity were directly related to the degradation of FQs. The most dominant ARGs in this experiment was qnrD and the relative abundance of qnrD in effluent of device-A, device-B, device-C and device-D were 93.0%, 94.4%, 85.6% and 89.0% lower than that in influent. Flavobacterium , Microbacterium , Dechloromonas , etc. were the key microorganisms for biological removal of FQs by VFCWs. [Display omitted] • Only one FQs degradation product was detected under low hydraulic load. • Six FQs degradation products were detected under high hydraulic load. • Degradation of FQs by vertical flow constructed wetlands reduced ecological risks. • Flavobacterium , Microbacterium , Dechloromonas , etc. played roles in FQs removal. • Cytochrome P450 was directly related to the degradation of fluoroquinolones (FQs). [ABSTRACT FROM AUTHOR]

A pilot scale experiment was conducted to evaluate the characteristics of contaminants removal in a continuously two-stage biological process composed of an anoxic biofilter (AF) and an biological aerated filter (BAF). This novel process was developed by introducing new composite packing material (MZF) into bioreactors to treat rural domestic wastewater. A comparative study conducted by the same process with ceramsite as packing material under the same conditions showed that a MZF system with a Fe proportion in the packing material performed better in chemical oxygen demand (COD) removal (average 91.5%), ammonia (NH4+-N) removal (average 98.3%), total nitrogen (TN) removal (average 64.8%) and total phosphorus (TP) removal (average 90%). After treatment of the MZF system, the concentrations of COD, NH4+-N, TN and TP in effluent were 20.3 mg/L, 0.5 mg/L, 11.5 mg/L and 0.3 mg/L, respectively. The simultaneously high efficiencies of nitrification, denitrification and phosphorus removal were achieved by the coupling effects of biological and chemical processes in the MZF system. The results of this study showed that the application of MZF might be a favorable choice as packing material in biofilters for treatment of rural domestic wastewater. [ABSTRACT FROM AUTHOR]

Antibiotics had attracted more and more attention in recent years due to their harmfulness. Fluoroquinolones (FQs), one class of antibiotics widely used in human and veterinary medicine, were found in various water bodies in China. Therefore, in order to found an efficient method for removing FQs in rural domestic wastewater and optimize the process parameters, ceramsite and soil were applied in vertical flow constructed wetlands (VFCWs) to study the effects of different hydraulic loads and different substrates on the removal of FQs and conventional pollutants. The results showed the VFCW-D filled with 45 cm soil layer and 15 cm ceramasite layer had the highest removal efficiency of conventional pollutants and FQs under low hydraulic load. Nevertheless, the removal efficiency of conventional pollutants was significantly declined for the VFCWs which contained soil substrates under high hydraulic load due to the soil pores were clogged by the accumulation of organic matter. Finally, VFCW-A filled with 60 cm ceramasite layer revealed good ability to remove conventional pollutants and FQs under high hydraulic load. Deinococcus played a vital role here due to its excellent removal effect on conventional pollutants. The microbial composition in the substrate changed greatly after adding antibiotics under high hydraulic load. Devosia , Pseudorhodoferax , Cellvibrio , Bosea , Caulobacter , Acinetobacter , Zoogloea , Arcobacter , Dechloromonas , Flavobacterium , Nakamurella , Chloroplast , Clostridium_sensu_stricto_1 , Pelosinus , UTCFX1 and Hypnocyclicus became the new dominated genera and were essential to remove pollutants. In summary, VFCW was an effective system to remove fluoroquinolones in rural domestic wastewater. [Display omitted] • Vertical flow constructed wetlands (VFCW) could remove fluoroquinolones well. • VFCW-D had the best pollutants removal efficiency under low hydraulic load. • VFCW-A had the best pollutants removal efficiency under high hydraulic load. • Deinococcus (Deinococcus-Thermus) had the excellent pollutants removal ability. • Soil pores were clogged by organic matter accumulation under high hydraulic load. [ABSTRACT FROM AUTHOR]

Integrated constructed wetlands (ICWs) are regarded as one of the most important removal technology for pollutants in rural domestic wastewaters. This study investigated the efficiency of an ICW consisting of a regulating pool, four surface and subsurface flow-constructed wetlands, and a stabilization unit for removing antibiotics and antibiotic resistance genes (ARGs) from rural domestic wastewaters. The results showed that antibiotics leucomycin, ofloxacin, lincomycin, and sulfamethazine, and ARGs sul1, sul2, tetM, and tetO were the predominant antibiotics and ARGs in the influent, respectively. The ICW system could significantly reduce most of the detected antibiotics and ARGs with their aqueous removal rates of 78 to 100 % and >99 %, respectively. Based on the measured concentrations, the total pollution loadings of antibiotics were 3,479 μg/day in the influent and 199 μg/day in the final effluent. Therefore, constructed wetlands could be a promising technology for rural wastewater in removing contaminants such as antibiotics and ARGs. [ABSTRACT FROM AUTHOR]

Agricultural runoff impacts rivers and lakes on a global scale, while in developing countries (e.g., China), rural domestic wastewater is often an additional source of pollution. Scholars and policy makers are now promoting the use of agricultural vegetated ditches (VDs) as a potential supplemental management practices for nutrients and pesticide reduction from agricultural sources; however, information on the efficacy of these systems for the treatment of rural wastewater loaded with nutrients and heavy metal(loid)s (HMLs) removal and standing stock (SS) in aquatic plants growing there is rare or unknown. These shortcomings in our understanding of these systems must be addressed if they are going to serve further as an effective tool for purifying rural domestic sewage laden with concentrations of HMLs. To address this knowledge gap, the present study deals with SS of ten HMLs in ten plant species growing in a VD receiving raw rural domestic wastewater, with the intention to revealing an appropriate period for ditch plant harvesting to maximize HM removal. Mean reduction efficiencies amount to TN (60.6%), NH 4 -N (63.3%), NO 3 -N (48.1%), TP (58.5%) and PO 4 -P (51.9%), with favorable treatment performance during the summer season. Concentrations of nutrients typically declined gradually with distance along the length of the VD. Furthermore, the annual average reduction amounted to Ni (50.6%), Cu (56.1%), Cr (63.3%), Zn (79.3%), Cd (67.5%), Pb (80.1%), As (60.3%), Fe (52.6%), Al (19.8%), and Mn (24.3%). Plant uptake and sediment retention were the major contributors for nutrient mitigation within the vegetated ditches, with subsequent bacterial interaction and transformation of pollutants. Accumulation of HMLs varied among species and plant parts. Overall, SSs of most HMLs in plant species were greater in either stems or roots than leaves, with maximum values recorded in SSs of Al, Fe, and Mn. Based on the seasonal fluctuation of the accumulated HMLs in different plant species, the approach of harvesting plant biomass in order to effectively target HMLs in August or early September is recommended. Overall, reported results suggest that VD is an effective ecosystem to mitigate HMLs and nutrients from raw rural domestic wastewater in a similar way as constructed wetlands, noting the potential incorporation into local best management practices. • The first study that investigates standing stock and metal removal in a VD treating rural wastewater. • Concentration and metal standing stock in plant parts varies among species and metals. • Concentration alone without including the total biomass could miscalculate the metal standing stock and the ability of the whole plant. • VDs mitigate nutrients and metals in a similar way as constructed wetlands. [ABSTRACT FROM AUTHOR]

Vegetated agricultural drainage ditches (VDs) are a relatively new best management practice for pesticide and nutrient mitigation that is receiving increasing global interest. However, VDs are seldom used during winter due to considerable deterioration of pollutants reduction efficiencies driven by low-temperature effects. Limited knowledge on the internal loading of nutrient in VDs due to vegetation decomposition calls for further evaluation. Here, we assessed plants growth characteristics and nutrient dynamics in a field-scale VD receiving nutrient-rich sewage and planted with the overwintering plants: Acorus gramineus , Myriophyllum aquaticum and Iris sibirica. Water purification performance showed average TN, NH 4 -N, NO 3 -N, TP and PO 4 -P reduction efficiencies of 44, 46, 43, 52 and 46%, respectively, over the winter period. Maximum reduction rates of TN and TP were 5.31 and 0.34 g−2 d−1, respectively. Of the total nutrient removal by plants of 5.37 × 103 kg N y−1 and 0.65 × 103 kg P y−1 from the VD system, A. gramineus contributed 65.7% and 72.1%, respectively. Nonetheless, substantial amounts of N and P retained within the aboveground biomass were released into the water column as ditch plant shoots decayed to deteriorate the water quality. All three species, A. gramineus , M. aquaticum and I. sibirica demonstrated considerable nutrient accumulation during winter and facilitated nutrient retention in the VD system. Consequently, they can be considered effective overwintering species of choice in VDs for purifying nutrient-rich water and potentially appropriate for vulgarizing elsewhere, particularly throughout the winter season. Unlabelled Image • VDs are an ecological treatment solution for rural regions under winter season (WS). • Three studied species demonstrate as effective plants for VD system under WS. • Shoot decay significantly released retained nutrient into the water column and impacted water quality. • Further research should continue to identify a wider range of suitable ditch species. [ABSTRACT FROM AUTHOR]

Vegetated drainage ditches (eco-ditches) have drawn much attention in recent years for the ability to remediate diffuse contaminants in rural wastewater through sediment retention, plant uptake and interception, and microbial metabolic activities. However, the effect of plant species on microbial community structure and nitrogen (N) retention in ditch sediment remains poorly understood. In this study, mesocosm plastic drums were planted with eight plant species commonly found in ditches and nurtured with wastewater for 150 days. Sediment total nitrogen (TN) was greatly increased after 150-day nurturing with rural wastewater, from 296.03 mg∙kg−1 (Iris japonica Thunb) to 607.88 mg∙kg−1 (Acorus gramineusO). This study also presents the effect of different plant species on sediment microbial communities, thus providing insight into N removal mechanisms in eco-ditch. Fifty-eight differentially abundant taxa were identified, and sediment microbial community structure for no plant (CK), Acg, Canna indica (Cai), and Typha latifolia L. (Tyl) was primarily linked to sediment NH4+-N and TN. Extremely small proportions of ammonia oxidizing bacteria (AOB) and nitrifying bacteria were detected for all treatments, but large proportions of Crenarchaeota, which comprises the widely existent ammonium oxidized archaea (AOA), were found in CK, Acg and Cai. The abundance of Nitrosotalea from Crenarchaeota presented positive correlations with sediment NH4+-N contents and ammonia oxidation function predicted by Faprotax, indicating Nitrosotalea might be the dominant ammonium-oxidizing microbes in sediment samples. The probable NH4+-N removal pathway in wastewater sediment was through a combined effect of AOA, nitrifying bacteria, and anammox. [ABSTRACT FROM AUTHOR]

Given long-term decentralized and centralized rural domestic wastewater (RDW) discharge, nitrogen is continuously depositing in sediments. RDW discharge is assumed to be an important source of ammonium in surface water; however, the effect of long-term RDW discharge on nitrogen pollution in sediments remains unknown. Batch incubations were conducted to investigate the characteristics of internal ammonium loading from long-term polluted sediments by RDW discharge. Four sediments were demonstrated to be heavily polluted by long-term RDW discharge, with total nitrogen (TN) values of 5350, 8080, 2730, and 2000 mg·kg -1 , respectively. The internal ammonium release from sediment was a slow and long process, and the risk of ammonium release from sediment during the dry season was significantly greater than that during the wet season. Though all selected sediments were heavily polluted by long-term RDW discharge, the relative contribution of internal ammonium loading from sediments was generally lower than that of external pollution. Hence, dredging is not suggested for RDW-polluted sediments except in response to an emergency. The excessive ammonium in the selected catchment was mainly from untreated and centralized black water in RDW. Centralized black waters in rural communities are highlighted to be separately treated or reused to maintain ammonium content at a safe level.