Dynamics and functions of bacterial communities in bark, charcoal and sand filters treating greywater

Simulation and optimisation of magnetic and experimental study of magnetic field coupling constructed wetland

This study developed a novel constructed wetland (CW) coupled with a magnetic field for treating domestic wastewater, and the magnetic field distribution was solved and optimised by the finite element method. Herein, we investigated the effects of optimising magnetic field optimisation and studied its impact on CW treatment performance and the responses of a microbial community. The optimisation results showed that the average magnetic field strength of the CW unit increases from 3 to 8 mT, and the proportion of areas with magnetic field strength greater than 5 mT also increases from 30% to 74%. The water quality analysis results showed that the removal of chemical oxygen demand (COD) and NH4+-N (p < 0.01) was significantly increased by the magnetic field (average 3 mT), increasing by 12.2% and 8.49%, respectively. Moreover, the removal of COD and NH4+-N (p < 0.01) was more significantly increased by M-VFCW(O) (average 8 mT), increasing by 15.58% and 49.1%, respectively. The magnetic field application shifted significantly the abundance of dominant bacteria in CWs. Relative abundance of dominant bacteria such as Proteobacteria (63.3%), Firmicutes (4.72%) and Actinobacteria (2.11%) that played an important role in organics removal and nitrification and denitrification-related bacteria such as Nitrospirae (1.48%) and Planctomycetes (9.58%) significantly promoted in M-VFCW(O). These results suggest that introducing a magnetic field into CWs may improve organics and nitrogen removal via the biological process, and the optimisation of the magnetic field was significant in enhancing the performance of VFCWs.

Microbial niches and dynamics of antibiotic resistance genes in a bio-enhanced granular-activated carbon biofilm treating greywater

Accumulation and transmission of antibiotic resistance genes (ARGs) in greywater treatment systems present risks for its reuse. In this study, a gravity flow self-supplying oxygen (O₂) bio-enhanced granular activated carbon dynamic biofilm reactor (BhGAC-DBfR) was developed to treat greywater. Maximum removal efficiencies were achieved at saturated/unsaturated ratios (R_St/Ust) of 1:1.1 for chemical oxygen demand (97.6 ± 1.5%), linear alkylbenzene sulfonates (LAS) (99.2 ± 0.5%), NH₄⁺-N (99.3 ± 0.7%) and total nitrogen (85.3 ± 3.2%). Microbial communities were significantly different at various R_St/Ust and reactor positions (P < 0.05). The unsaturated zone with low R_St/Ust showed more abundant microorganisms than the saturated zone with high R_St/Ust. The reactor-top community was predominant by aerobic nitrification (Nitrospira) and LAS biodegradation (Pseudomonas, Rhodobacter and Hydrogenophaga) related genera; but reactor-bottom community was predominant by anaerobic denitrification and organics removal related genera (Dechloromonas and Desulfovibrio). Most of the ARGs (e.g., intI-1, sul1, sul2 and korB) were accumulated in the biofilm, which were closely associated with microbial communities at reactor top and stratification. The saturated zone can achieve over 80% removal of the tested ARGs at all operation Phases. Results suggested that BhGAC-DBfR can provide assistance in blocking the environment dissemination of ARGs during greywater treatment.

Granular media filtration for on-site treatment of greywater: A review

Rapid urbanization and industrialization have put pressure on water resources and centralized wastewater treatment facilities and the need for greywater treatment at decentralized levels is increasing. This paper reviews the studies that used granular filtration for the treatment of greywater. Filter media characteristics that helps in the selection of suitable sustainable and environmental friendly materials without compromising the quality of treated greywater is first reported. The effect of type of filter media, media size and media depth along with the effect of operating conditions are discussed in detail. The choice, role and effect of different pre-treatment alternatives to granular media filtration are also presented. The efficiency of the filters to remove different physicochemical and microbial parameters was compared with different reuse guidelines and standards. Reported studies indicate that not only filter media characteristics and operating conditions but also the quality of raw greywater significantly influence the filter performance. Based on the source of greywater and desired reuse option, different granular media filtration alternatives are suggested. Operation of filters with properly selected media at optimum conditions based on the source of greywater helps filter in achieve the different reuse standards.

New directions and challenges in engineering biologically-enhanced biochar for biological water treatment

Cost-effective, efficient, and sustainable water treatment solutions utilising existing materials and technology will make it easier for low and middle-income countries to adopt them, improving public health. The ability of biochar to mediate and support microbial degradation of contaminants, combined with its carbon-sequestration potential, has attracted attention in recent years. Biochar is a possible candidate for use in cost-effective and sustainable biological water treatment, especially in agrarian economies with easy access to abundant biomass in the form of crop residues and organic wastes. This review evaluates the scope, potential benefits (economic and environmental) and challenges of sustainable biological water treatment using 'Biologically-Enhanced Biochar' or BEB. We discuss the various processes occurring in BEB systems and demonstrate the urgent need to investigate microbial degradation mechanisms. We highlight the need to correlate biochar properties to biofilm development, which can eventually determine process efficiency. We also demonstrate the various opportunities in adopting BEB as a cheaper and more viable alternative in Low and Middle Income Countries and compare it to the current benchmark, 'Biological Activated Carbon'. We focus on the recent advances in the areas of data science, mathematical modelling and molecular biology to systematically and sustainably design BEB filters, unlike the largely empirical design approaches seen in water treatment. 'Sequential biochar systems' are introduced as specially designed end-of-life techniques to lower the environmental impact of BEB filters and examples of their integration into biological water treatment that can fulfil zero waste criteria for BEBs are given.

Human- and infrastructure-associated bacteria in greywater

Greywater, the wastewater from sinks, showers and laundry, is an understudied environment for bacterial communities. Most greywater studies focus on quantifying pathogens, often via proxies used in other wastewater, like faecal indicator bacteria; there is a need to identify more greywater-appropriate surrogates, like Staphylococcus sp. Sequencing-based studies have revealed distinct communities in different types of greywater as well as in different parts of greywater infrastructure, including biofilms on pipes, holding tanks and filtration systems. The use of metagenomic sequencing provides high resolution on both the taxa and genes present, which may be of interest in cases like identifying pathogens and surrogates relevant to different matrices, monitoring antibiotic resistance genes and understanding metabolic processes occurring in the system. Here, we review what is known about bacterial communities in different types of greywater and its infrastructure. We suggest that wider adoption of environmental sequencing in greywater research is important because it can describe the entire bacterial community along with its metabolic capabilities, including pathways for removal of nutrients and organic materials. We briefly describe a metagenomic dataset comparing different types of greywater samples in a college dormitory building to highlight the type of questions these methods can address. Metagenomic sequencing can help further the understanding of greywater treatment for reuse because it allows for identification of new pathogens or genes of concern.

Greywater as a sustainable source for development of green roofs: Characteristics, treatment technologies, reuse, case studies and future developments

Municipal activities are one of the most important water users worldwide; thus, the treatment and reuse of greywater for non-potable purposes helps to reduce a remarkable amount of consumed water within urban communities. To achieve greywater reuse standards, and remove surfactants, micropollutants, organic matters, microorganisms and other pollutants various methods including physical, chemical and biological processes have been used. Treated greywater can be used on site for different purposes: carwash, toilet flushing, fire protection, green roofs, green walls, non-food irrigation etc. Among them, the use of greywater is very important in the expansion of the green roofs. Green roofs offer many benefits to urban areas such as decreasing air pollution, reducing building cooling needs, promoting mental health of habitants, noise reduction and aesthetics improvement. Therefore, this article provides an overview mainly from two aspects, the possibilities of greywater reuse by studying the characteristics and available options for greywater treatment and its benefits toward the developing green roofs.

Change in microbial profile and environmental conditions in a constructed wetland system treating greywater

The objective of this work was to verify the relationships between environmental conditions and microbial processes along a raw-light greywater flow in an improved constructed wetland (CW) system. Physicochemical analysis and high-throughput DNA sequencing were performed in the different zones to investigate the environmental conditions and microbial communities. The results showed that the system operated predominantly under anaerobic conditions, with redox potential (Eh) increasing from the inlet (-342.9 mV) to the outlet (-316.4 mV). Conversely, the chemical oxygen demand (COD) decreased along the greywater flow, suggesting negative correlation between these characteristics. The zones of the evapotranspiration and treatment tank (CEvaT) were characterized by lower community diversity and richness and by the presence of specific groups: Proteobacteria and Synergistetes related to the first steps of the conversion of organic carbon, in the bottom layer inside the anaerobic chamber (AnC); methanogens (Methanosaeta and Methanobacterium) and sulphate-reducing bacteria (Desulfovibrio, Desulforhabdus and Desulfomonile) in the middle layer; and microorganisms associated with the nitrogen cycle and oxygen release (Acinetobacter, Novosphingobium, Candidatus Nitrososphaera) in the top layer. On the other hand, the increase of the ORP and decrease of organic matter concentrations were associated with higher community diversity and richness in the middle layer of the CW, which showed higher abundance of microorganisms involved in methane (Methylobacterium and Candidatus Koribacter) and sulphur (Rhodoblastus and Thiobacillus) oxidation.

Influence of slow sand filter cleaning process type on filter media biomass: backwashing versus scraping

Biomass was assessed as a new approach for evaluating backwashed slow sand filters (BSF). Slow sand filtration (SSF) is a simple technology for water treatment, where biological mechanisms play a key role in filtration efficiency. Backwashed slow sand filters were previously recommended for small-scale filters (~1 m² of filtration area) as an alternative to conventional filters that are usually cleaned by scraping (ScSF). Biomass was never evaluated in BSF, which is a gap in the knowledge of this technology, considering the importance of its biological mechanisms. Therefore, for the first time, two filters operating under the same conditions were used to compare the influence of backwashing on biomass; one filter was cleaned by backwashing and the other by scraping. Biomass along the filter media depth (40 cm) was assessed by different techniques and compared in terms of cellular biomass (by chloroform fumigation), volatile solids, bacterial community (by 16S rRNA gene sequencing), and observations by scanning electron and fluorescence microscopy. Filters were also monitored and compared regarding filtered water quality and headloss; their differences were related to the different cleaning processes. Overall, filtered water quality was acceptable for slow sand filter standards (turbidity < 1 NTU and total coliform removal > 1 log). However, headloss developed faster on scraped filters, and biomass was different between the two filters. Backwashing did not significantly disturb biomass while scraping changed its surface sand layers. Cell biomass was more abundant and spread across the filtration depth, related to lower headloss, turbidity, and cyanobacterial breakthrough. These results agreed with the water quality and microscopy observations. The bacterial community was also less stratified in the backwashed filter media. These results expand the knowledge of backwashing use in slow sand filters, demonstrating that this process preserves more biomass than scraping. In addition, biomass preservation can lead to bacterial selectivity and faster filter ripening. Considering the importance of biomass preservation on slow sand filtration and its biological filtration mechanisms, the results presented in this paper are promising. The novel insight that BSF can preserve biomass after backwashing may contribute to increasing its application in small communities.

Viability of a Single-Stage Unsaturated-Saturated Granular Activated Carbon Biofilter for Greywater Treatment

Compared with conventionally collected sewage, source-diverted greywater has a higher potential for on-site treatment and reuse due to its lower contaminant levels and large volume. A new design of granular activated carbon (GAC) biofilters was developed by incorporating unsaturated and saturated zones in a single stage to introduce an efficient, passive, and easy-to-operate technology for greywater on-site treatment at the household scale. The design was customized for its intended application considering various aspects including the reactor’s configuration, packing media, and feeding strategy. With the highest hydraulic and organic loadings of 1.2 m3 m−2 d−1 and 3.5 kg COD m−2 d−1, respectively, and the shortest retention time of 2.4 h, the system maintained an average total chemical oxygen demand removal rate of 94% with almost complete removal of nutrients throughout its 253 days of operation. The system showed a range of reduction efficacy towards five surrogates representing viruses, bacteria, and Cryptosporidium and Giardia (oo)cysts. A well-functioning biofilm was successfully developed, and its mass and activity increased over time with the highest values observed at the top layers. The key microbes within the biofilter were revealed. Feasibility of the proposed technology was investigated, and implications for design and operation were discussed.

Improvement of Black-Odor Water by Pichia Strain GW1 under Optimized NH3-N Degradation Conditions

In this study, a yeast strain with an outstanding NH₃-N degradation ability was isolated from the sediment of a black-odor water channel in Guangdong Province, China. Based on phenotypic and phylogenetic analysis, this strain was identified as Pichia kudriavzevii GW1. The optimum conditions for NH₃-N degradation by the GW1 strain were as follows: 0.3% inoculum concentration, 1.5 L/min aeration, pH 7, and a temperature of 35°C. Under optimized conditions, the GW1 strain degraded 95.5% of the NH₃-N. The strain was then added to simulated black-odor water under optimal degradation conditions to investigate changes to the bacterial community over time. 16S rRNA sequencing of samples collected on days 0, 7, 14, and 21 showed that, in the presence of the GW1 strain, the relative abundances of the phyla Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes increased in the black-odor water. In addition, the relative abundance of Propionivibrio, a known NH₃-N degrading genus, increased. This study will facilitate the use of microbiological methods to repair black-odor water.

Design of a bioaugmented multistage biofilter for accelerated municipal wastewater treatment and deactivation of pathogenic microorganisms

Biological treatment of municipal wastewater for reuse in irrigation is highly required, especially with the current global financial and water shortage crises. Bioaugmentation is a simple and cost-effective technology which could be a useful tool in alleviating this challenge. Thus, this study aimed to enhance the biological treatment of municipal wastewater using a bioaugmented substance supplemented in a three-stages bio-filter consisting of a sedimentation step followed by gravel biofiltration and then sand biofiltration at a laboratory scale. Also, a toxicity assay, the antimicrobial effect of the bioaugmented substance against pathogenic microorganisms, and identification of the synergistic effect of the bacterial consortium involved in the bioaugmented substance were studied. The bioaugmented substance was nontoxic and had an antimicrobial effect against the tested potentially pathogenic microorganisms (Escherichia coli, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, and Candida albicans). The minimum effective concentration of the bioaugmented substance for organic, inorganic and microbial pollutants removal from high strength wastewater was 2.5 ppm with a contact time of 6-8 h. The removal efficiencies of H₂S, COD, BOD₅, total solids (TS), total dissolved solids, total suspended solids, ammonia, nitrate, phosphorus, and oil and grease reached 85, 93.4, 83.5, 37, 49.2, 93.4, 100, 55.7, 76.6 and 76.6%, respectively in the treated effluent after sand biofiltration. The physicochemical parameters of the treated wastewater effluent were below the Egyptian recommended limits (Law 84/1984) for use in irrigation. However, COD and BOD values were 90.33 and 38.46 mgO₂/L, respectively, and were still above the regulations (COD ≤60 and BOD ≤20). The high fecal coliforms count in the wastewater influent (8.4 × 10⁸ MPN-index/100 mL) were 95.1% removed after the sedimentation stage, and 99.99% removal was achieved after gravel and sand biofiltration. Thus, this study successfully designed a bioaugmented multistage biofiltration system for the effective removal of pollutants from wastewater, especially in resource-limited areas.

Biochar filters as an on-farm treatment to reduce pathogens when irrigating with wastewater-polluted sources

Microbial contamination of vegetables due to irrigation with wastewater-polluted streams is a common problem around most cities in developing countries because wastewater is an available source of water and nutrients but wastewater treatment is often inadequate. On-farm treatment of polluted water is a feasible option to manage microbial risks in a multi-barrier approach. Current evidence indicates good suitability of biochar filters for microbe removal from wastewater using the hydraulic loading rate (HLR) designed for sand filters, but their suitability has not been tested under on-farm conditions. This study evaluated the combined effect of several variables on removal of microbial indicators from diluted wastewater by biochar filtration on-farm and the correlations between removal efficiency and HLR. Columns of biochar with three different effective particle diameters (d₁₀) were fed with diluted wastewater at 1x, 6x, and 12x the design HLR and two levels of water salinity (electrical conductivity, EC). Influent and effluent samples were collected from the columns and analyzed for bacteriophages (ɸX174 and MS2), Escherichia coli, Enterococcus spp., and Saccharomyces cerevisiae. Microbe removal decreased with increasing HLR, from 2 to 4 to 1 log₁₀ for bacteria and from 2 to 0.8 log₁₀ for viruses, while S. cerevisiae removal was unaffected. Effective particle diameter (d₁₀) was the main variable explaining microbe removal at 6x and 12x, while EC had no effect. Correlation analysis showed removal of 2 log₁₀ bacteria and 1 log₁₀ virus at 3x HLR. Thus biochar filters on-farm would not remove significant amounts of bacteria and viruses. However, the design HLR was found to be conservative. These results, and some technical and management considerations identified, can assist in the development of a scientific method for designing biochar filters for on-farm and conventional wastewater treatment.

On-farm wastewater treatment using biochar from local agroresidues reduces pathogens from irrigation water for safer food production in developing countries

In this study, the suitability of an anaerobic biofilter (AnBF) as an efficient and low-cost wastewater treatment for safer irrigation water production for Sub-Saharan Africa was investigated. To determine the influence of different ubiquitous available materials on the treatment efficiency of the AnBF, rice husks and their pyrolysed equivalent, rice husk biochar, were used as filtration media and compared with sand as a common reference material. Raw sewage from a municipal full-scale wastewater treatment plant pretreated with an anaerobic filter (AF) was used in this experiment. The filters were operated at 22 °C room temperature with a hydraulic loading rate of 0.05 m·h^-1 for 400 days. The mean organic loading rate (OLR) of the AF was 194 ± 74 and 63 ± 16 g_COD·m^-3·d^-1 for the AnBF. Fecal indicator bacteria (FIB) (up to 3.9 log₁₀-units), bacteriophages (up to 2.7 log₁₀-units), chemical oxygen demand (COD) (up to 94%) and turbidity (up to 97%) could be significantly reduced. Additionally, the essential plant nutrients nitrogen and phosphorous were not significantly affected by the water treatment. Overall, the performance of the biochar filters was significantly better than or equal to the sand and rice husk filters. By using the treated wastewater for irrigating lettuce plants in a pot experiment, the contamination with FIB was >2.5 log-units lower (for most of the plants below the detection limit of 5.6 MPN per gram fresh weight) than for plants irrigated with raw wastewater. Respective soil samples were minimally contaminated and nearly in the same range as that of tap water.

Enhanced biofilm formation and denitrification in biofilters for advanced nitrogen removal by rhamnolipid addition

Denitrification biofilters (DNBFs) are widely used in advanced nitrogen removal of wastewater with low C/N and effective biofilm formation is critical to their long-term operation. Hereby the influence of rhamnolipid addition in DNBFs was investigated for the first time. Gradient concentrations (0, 20, 40, 80, 120 mg/L) of rhamnolipid were applied to investigate nitrogen removal, biofilm properties and microbial community of lab-scale DNBFs. A significant increase of nitrogen removal was observed in rhamnolipid-treated DNBFs (p < 0.05). Total solid (TS), extracellular polymeric substances (EPS) and adhesion force of biofilms in DNBF with 120 mg/L rhamnolipid reached the maximum, which were 2.17, 2.15 and 3.36 times of those in the control, respectively. Moreover, rhamnolipid exhibited an improvement in abundance of Simplicispira and Gemmatimonas which were responsible for enhanced biofilm formation and denitrification. The results suggested that rhamnolipid addition can be a novel strategy to improve the start-up and denitrification performance of DNBFs.

The response of nitrogen removal and related bacteria within constructed wetlands after long-term treating wastewater containing environmental concentrations of silver nanoparticles

The wide application of consumer products containing silver nanoparticles (AgNPs) inevitably results in their release into sewer systems and wastewater treatment plants, where they would encounter (and cause potential negative impacts) constructed wetlands (CWs), a complex biological system containing plants, substrate and microorganisms. Herein, the long-term effects of environmental AgNPs concentrations on nitrogen removal, key enzymatic activities and nitrogen-related microbes in constructed wetlands (CWs) were investigated. The short-term exposure (40 d) to AgNPs significantly inhibited TN and NH₄⁺-N removal, and the inhibition degree had a positive relationship with AgNPs levels. After about 450 d exposure, 200 μg/L AgNPs could slightly increase average TN removal efficiency, while presence of 50 μg/L AgNPs showed no difference, compared to control. The NH₄⁺-N removal in all CWs had no difference. The present study indicated that short-term AgNPs loading evidently reduced nitrogen removal, whereas long-term exposure to AgNPs showed no adverse impacts on NH₄⁺-N removal and slightly stimulated TN removal, which was related to the increase of corresponding enzymatic activities. After exposing AgNPs for 450 d, the abundance of relative functional genes and the composition of key community structure were determined by qPCR and high-throughput sequencing, respectively. The results showed that the abundance of amoA and nxrA dramatically higher than control, whereas the abundance of nirK, nirS, nosZ and anammox 16S rRNA was slightly higher than control, but had no statistical difference, which accorded with the TN removal performance. The microbial community analysis showed that different AgNPs concentrations could affect the microbial diversity and structure. The changes of the relative abundance of nitrogen-related genera were associated with the impacts of AgNPs on the nitrogen removal performance. Overall, the AgNPs loading had impacts on the key enzymatic activities, the abundance of nitrogen-related genes and microbial community, thus finally affected the treatment performance of CWs.

Bacterial community activity and dynamics in the biofilm of an experimental hybrid wetland system treating greywater

The objectives of this study were to determine the biofilm microbial activity and bacterial community structure and successions in greywater treatment filters and to relate the treatment efficiency to the bacterial community parameters. This 10-month study was performed in a newly established experimental system for domestic greywater treatment that consisted of three parallel vertical flow filters (VFs) followed by a horizontal flow filter (HF). A rapid increase in the bacterial community abundance occurred during the first 85 days of filter operations, followed by a short-term decrease and the stabilization of the 16S rRNA gene copy numbers at average levels of 1.2 × 10⁹ and 3.2 × 10⁸ copies/g dw in VFs and HF, respectively, until the end of the experiment. The dominant bacterial phyla and genera differed between the VFs and HF. The temporal variation in the bacterial community structure was primarily related to the species replacement, and it was significantly affected by the influent organic carbon and nitrogen compounds in the VFs and the ammonia and organic carbon in the HF filters. Despite the differences in the community structure and assembly mechanisms, the temporal dynamics of the bacterial community showed high congruence between the filter types. The treatment efficiency was related to the biofilm bacterial community diversity and abundance and the abundance of certain bacterial genera in the VF filters. The results suggest that the dominant pathway of nitrogen removal by greywater treatment VFs occurs via coupled heterotrophic nitrification and denitrification, while the contribution of aerobic denitrification is temporally variable in these filters.

Potential of Biochar Filters for Onsite Wastewater Treatment: Effects of Biochar Type, Physical Properties and Operating Conditions

The potential of biochar as a filter medium for onsite wastewater treatment was investigated in five sub-studies. Sub-study 1 compared pollutant removal from wastewater using pine-spruce biochar, willow biochar and activated biochar (undefined biomass) filters. Sub-study 2 investigated the effects of particle size (0.7, 1.4 and 2.8 mm) on pollutant removal using pine-spruce biochar filters. In sub-studies 3 and 4, the effects of the hydraulic loading rate (HLR; 32–200 L m−2) and organic loading rates (OLR; 5–20 g biochemical oxygen demand (BOD5) m−2) on pollutant removal using pine-spruce biochar filters were investigated, while sub-study 5 compared pollutant removal in pine-spruce biochar filters and in sand. The removal of chemical oxygen demand (COD), total nitrogen (Tot-N), ammonium nitrogen (NH4-N), phosphates (PO4-P) and total phosphorus (Tot-P) was monitored in all sub-studies. All types of biochar and all particle sizes of pine-spruce biochar achieved a high degree of removal of organic material (COD > 90%). Removal of Tot-P and PO4-P was higher in willow biochar and activated biochar (>70%) than in pine-spruce biochar during the first two months, but then decreased to similar levels as in pine-spruce biochar. Among the particle sizes tested, 0.7 mm pine-spruce biochar showed the lowest amount of Tot-P removal, while 2.8 mm pine-spruce biochar showed the lowest level of NH4-N removal. Different OLRs and HLRs did not influence COD removal (94–95%). Pine-spruce biochar showed a better degree of removal of Tot-N than sand. In conclusion, biochar is a promising filter medium for onsite wastewater treatment as a replacement or complement to sand, achieving high and robust performance regardless of the parent material, particle size or loading conditions.

Biological filters and their use in potable water filtration systems in spaceflight conditions

Providing drinking water to space missions such as the International Space Station (ISS) is a costly requirement for human habitation. To limit the costs of water transport, wastewater is collected and purified using a variety of physical and chemical means. To date, sand-based biofilters have been designed to function against gravity, and biofilms have been shown to form in microgravity conditions. Development of a universal silver-recycling biological filter system that is able to function in both microgravity and full gravity conditions would reduce the costs incurred in removing organic contaminants from wastewater by limiting the energy and chemical inputs required. This paper aims to propose the use of a sand-substrate biofilter to replace chemical means of water purification on manned spaceflights.

Enhancement of microbial nitrogen removal pathway by vegetation in Integrated Vertical-Flow Constructed Wetlands (IVCWs) for treating reclaimed water

Constructed wetland is an efficient way to lower N load from wastewater treatment plants. Here, the nitrogen removal rate and nitrogen balance, as well as the microbial community structure in IVCWs planted with different vegetation for treating reclaimed water were investigated. The results showed that IVCWs planted with vegetation generally achieved a higher TN removal rate than unplanted treatment, especially for Canna indica L. with 10.35% enhancement. Moreover, the microbial process proportion (83.87-87.94%) is the main N removal pathway in IVCW, and vegetation planting could increase 8.16% of it in average. The combination of quantitative polymerase chain reaction (qPCR) and high-throughput sequencing analysis revealed that IVCW planted with Canna indica L. showed the highest microbial abundant and biodiversity. The related denitrification genus Pseudomonas, Acinetobacter, Rhizobium, Bacillus and Rhodopseudomonas might be responsible for the high biological removal rate of nitrogen.

Potential of biochar filters for onsite sewage treatment: Adsorption and biological degradation of pharmaceuticals in laboratory filters with active, inactive and no biofilm

This study investigated the potential of biochar filters as a replacement or complement for sand filters for removal of pharmaceutically active compounds (PhACs) from wastewater in onsite sewage facilities (OSSF). Specifically, the study investigated the effects of biodegradation, adsorption and a combination of these processes on removal of four model PhACs from wastewater in biochar filters operated under hydraulic loading conditions mimicking those found in onsite infiltration beds. Concentrations and removal of the four PhACs (i.e. carbamazepine, metoprolol, ranitidine and caffeine) were investigated over 22weeks in four treatments: biochar (BC) with active or inactive biofilm (BC-active-biofilm, BC-inactive-biofilm), biochar without biofilm (BC-no-biofilm) and sand with active biofilm (Sand-active-biofilm). The adsorption of carbamazepine was high in BC-no-biofilm (99% removal after 22weeks), while biodegradation was very low in Sand-active-biofilm (7% removal after 22weeks). Removal of carbamazepine in BC-active-biofilm was high and stable over the 22weeks (>98%), showing a significant role of biofilm in filter biogeneration. However, carbamazepine removal declined over time in BC-inactive-biofilm, from 99% in week 13 to 73% in week 22. Metoprolol was poorly degraded in Sand-active-biofilm (37% after 22weeks), while adsorption seemed to be the major pathway for removal of metoprolol in biochar. Ranitidine and caffeine were efficiently removed by either adsorption (97% and 98%, respectively, after 22weeks) or biodegradation (99% and >99%, respectively, after 22weeks). In conclusion, biochar is a promising filter medium for OSSF, especially for persistent PhACs such as carbamazepine and metoprolol.

Treatment of municipal wastewater in full-scale on-site sand filter reduces BOD efficiently but does not reach requirements for nitrogen and phosphorus removal

A traditional sand filter for treatment of household wastewater was constructed in the fall of 2012 at Biolinja 12, Turku, Finland. Construction work was led and monitored by an authorized wastewater treatment consultant. The filter was placed on a field bordered by open ditches from all sides in order to collect excess rain and snowmelt waters. The filter was constructed and insulated from the environment so that all outflowing water was accounted for. Untreated, mainly municipal, wastewater from Varissuo suburb was pumped from a sewer separately via three septic tanks (volume = 1 m³ each) into the filters. Normally, wastewater was distributed to ground filters automatically according to pre-programmed schedule. Initially, the daily flow was 1200 L day^-1 to reflect the average organic load of a household of five persons (load: ca 237 g day^-1 BOD; 73 g day^-1 total N; and 10.4 g day^-1 total P). Later in the test, the flow rate was decreased first to 900 and then to 600 L day^-1 to better reflect the average volume produced by five persons. Volumes of inlet wastewater as well as treated water were monitored by magnetic flow meters. Samples were withdrawn from the inlet water, from the water entering the filters after the third septic tank, and from the outflowing water. After an initial adaption time, the reductions in BOD and chemical oxygen demand were constantly between 92 and 98%, showing that the biological degradation process in the filters functioned optimally and clearly comply with the national and EU standards. The reduction in total nitrogen and total phosphorus, however, reached required levels only during the first months of testing, apparently when buildup of microbial biomass was still ongoing. After this initial period of 3 months showing satisfactory reduction levels, the reduction of total nitrogen varied between 5 and 25% and total phosphorus mostly between 50 and 65%. Nitrification was efficient in the filter, but as indicated by high nitrate levels and poor nitrogen reductions, denitrification was inefficient or absent. During the winter period, the temperature in the filter dropped to near freezing, but at all time points, the flow of water was unaffected by freezing. During snowmelt and heavy rain, occasional flooding was observed. Such situations may lead to dilution rather than purification of the wastewater. In conclusion, the sand filter tested worked well for reduction of the organic load in municipal wastewater but failed to sufficiently reduce nitrogen and phosphorus levels.

Simulation and verification of hydraulic properties and organic matter degradation in sand filters for greywater treatment

To evaluate the treatment performance of vertical flow sand filters, the HYDRUS wetland module was used to simulate treatment in an experimental set-up. The laboratory filters were intermittently dosed with artificial greywater at a hydraulic loading rate of 0.032 m³ m⁻² day⁻¹ and an organic loading rate of 0.014 kg BOD5 m⁻² day⁻¹. The hydraulic properties of the filter were characterised, as were inflow and outflow concentrations of chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia, nitrate and total nitrogen. The inverse simulation function of the HYDRUS software was used to calibrate the water flow model. The observed effect of water flowing faster along the column wall was included in the inverse simulations. The biokinetic model was calibrated by fitting heterotrophic biomass growth to measurements of potential respiration rate. Emphasis was put on simulating outflow concentrations of organic pollutants. The simulations were conducted using three models of varying degree of calibration effort and output accuracy. The effluent concentration was 245 mg COD L⁻¹ for the laboratory filters, 134 mg COD mg L⁻¹ for the model excluding wall flow effects and 338 mg COD mg L⁻¹ for the model including wall flow effects.

Microbial community analysis of a full-scale DEMON bioreactor

Full-scale applications of autotrophic nitrogen removal technologies for the treatment of digested sludge liquor have proliferated during the last decade. Among these technologies, the aerobic/anoxic deammonification process (DEMON) is one of the major applied processes. This technology achieves nitrogen removal from wastewater through anammox metabolism inside a single bioreactor due to alternating cycles of aeration. To date, microbial community composition of full-scale DEMON bioreactors have never been reported. In this study, bacterial community structure of a full-scale DEMON bioreactor located at the Apeldoorn wastewater treatment plant was analyzed using pyrosequencing. This technique provided a higher-resolution study of the bacterial assemblage of the system compared to other techniques used in lab-scale DEMON bioreactors. Results showed that the DEMON bioreactor was a complex ecosystem where ammonium oxidizing bacteria, anammox bacteria and many other bacterial phylotypes coexist. The potential ecological role of all phylotypes found was discussed. Thus, metagenomic analysis through pyrosequencing offered new perspectives over the functioning of the DEMON bioreactor by exhaustive identification of microorganisms, which play a key role in the performance of bioreactors. In this way, pyrosequencing has been proven as a helpful tool for the in-depth investigation of the functioning of bioreactors at microbiological scale.