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Decentralized wastewater treatment systems (DWTS) are significant contributors to the eutrophication of surface water bodies due to a lack of treatment mechanisms that target dissolved phosphorus removal. Existing advanced treatment systems are expensive to operate, large in nature, and require frequent maintenance, making them unattractive to DWTS owners. This study aims to investigate the development of a continuous flow treatment system that uses electrocoagulation (EC) to remove dissolved phosphorus from small wastewater streams such as septic tank effluent (STE). Operational parameters, including system hydraulic retention time (HRT), applied current density, and wastewater composition, were optimized to maximize total phosphorus (TP) removal most cost-effectively. Using an HRT of 10 min, an applied current density of 2.0 mA/cm2, and an influent concentration of 20 mg/L, the orthophosphate (OP) and TP removal percentages achieved were 99.9 and 88.1%, respectively. Under these conditions, the average effluent Al3+ concentration in the treated effluent was measured to be 1.0 mg/L while the total suspended solids concentration was measured to be 51 mg/L. The operation cost was estimated to be 0.056 CAD/m3. The results demonstrate that the EC reactor is effective in removing dissolved phosphorus from wastewater and is therefore a viable option in mitigating the risk of downstream eutrophication caused by inadequately treated STE. [ABSTRACT FROM AUTHOR]

The Living Wall (LW) garden system has been employed as a post-treatment system to improve the effluent quality of septic tanks. This improvement primarily involves reducing nutrient levels, as well as facilitating the removal of organic matter and solids in accordance with effluent discharge guidelines. The objective of this study was to investigate the treatment performance of the LW system connected to a septic tank, along with an examination of the microbial communities within the LW units. A laboratory-scale LW system, comprising LW1, LW2, and LW3 units, was employed. The system was fed with effluent obtained from septic tanks and varied by theoretical hydraulic retention time (HRT) of 6, 12, and 24 h. The TCOD, SCOD, TSS, TVS, TKN, and TP removal efficiencies of the LWs were achieved at 62 ± 24, 42 ± 19, 72 ± 21, 66 ± 15, 80 ± 15, and 58 ± 21%, respectively. To classify microbial communities in the soil and gravels collected from each LW unit, the Illumina MiSeq System Sequencer was employed. Nitrospirota was consistently found in all LW units, aiding in the conversion of nitrogen. Fusobacteriota were detected in specific layers of the LW units, indicating varying oxygen levels in the LW system. Highlights: • Living Walls (LWs) effectively eliminate organics, nutrients, and solids to meet the national discharge standard. • Expanding LW units improves nitrogen removal, and microbial communities are crucial for nitrogen removal in LW units. [ABSTRACT FROM AUTHOR]

This paper investigated a combined process of a modified attached-growth anoxic-oxic-anoxic reactor (AG-AOAR) as a sustainable and effective post-treatment system for septic tank effluent was developed. The AG-AOAR was operated by varying hydraulic retention times (HRTs) from 24 to 72 h. The results showed that the AG-AOAR achieved highest removal efficiencies of 84, 66 and 91% of chemical oxygen demand (COD), total nitrogen (TN) and ammonium nitrogen (NH4-N), respectively, under the HRT of 72 h, resulting its effluent meeting the international and national discharge quality standards for non-sewered sanitation system. The Stover-Kincannon model was applicable to describe the kinetic constants of COD, TN, and NH4-N removal in the AG-AOAR (R² > 0.85). Accordingly, the maximum utilization rates (μmax) were determined to be 41.1, 0.15 and 0.50 g/(L-d) for COD, TN and NH4-N removals, respectively, while the saturation constants (KB) were 57.7, 0.12 and 0.51 g/(L-d), respectively. These constant values could be applied for the design of the AG-AOAR to produce treated effluent meeting desired standards. [ABSTRACT FROM AUTHOR]

Vertical Garden Constructed Wetland (VGCW) system has been used as a secondary treatment system to improve effluent quality of septic tanks and cesspools by enhancing nutrients, organic and solid removal according to the guidelines of effluent discharge. This study aimed to investigate the treatment performance of the VGCWs by integrating with diverse plant species and modified media used as secondary treatment for conventional or solar septic tanks. In the study, laboratory-scale VGCW utilizing soil as the media and planted with Water Pennywort were operated at hydraulic retention times (HRT) of 6, 12, and 24 h, while modified planted vertical garden constructed wetlands (mpVGCW) operated at an HRT of 36 h, was fed with effluent collected from a septic tank. The treatment performance of VGCWs treating effluent from the septic tank and operating at an HRT of 24 h was found to achieve the highest removal efficiencies for organic matter, nutrients, and solids (up to over 90%), compared to an HRT of 6 or 12 h. Moreover, the highest log reduction of E.coli of 2.8 was also observed at the 24 h HRT, in comparison to HRTs of 6 or 12 h. The Spider Ivy, Coleus, and Selaginella frosty could be planted in the mpVGCW system to enhance the overall treatment efficiencies with consistently showed high removal efficiencies for TCOD (91.37–93.39%), TKN (97.1–97.8%), and TP (87.18–88.58%). These results suggested the potential of the VGCWs as a secondary treatment system for polishing septic tank effluent and improving environmental quality. • Vertical Garden Constructed Wetlands (VGCWs) operated at a 24-h-HRT exhibited the highest removal efficiencies for TCOD (85%), SCOD (70%), TKN (90%), and TP (80%). • Modified planted vertical garden constructed wetlands (mpVGCWs) efficiently removed the pollutantswith Spider Ivy, Coleus, and Selaginella frosty displaying high removal rates for TCOD (91.37–93.39%), TKN (99.32%), and TP (87.18–88.58%). • Both systems are applicable for treating effluent from communal septic tanks, providing an eco-friendly alternative for environmental protection. [ABSTRACT FROM AUTHOR]

The impact of individual septic tank effluent on groundwater quality was investigated in the rural area of the Ain Soltane municipality in Algeria. This area has an important number of individual septic tanks, and it is devoid of a drinking water supply and sewerage systems. The septic tank is a pre-treatment solution of sewage by bacteria living without oxygen (anaerobic). The alluvial aquifer in this area is covered by a layer of good permeability on the surface, which can pollute groundwater by vertical transport of pollutants through the soil, including microbial contamination. Groundwater samples were collected from 33 wells in the dry period of 2016. The monitoring of groundwater quality has shown a significant degree of organic and inorganic pollution in the majority of wells, with very high concentrations of sulphate and chloride exceeding 450 mg/l and 250 mg/l respectively. The analyzes also show the presence of bacterial germs in the groundwater of which the origin is faecal (faecal coliform densities are above 10 organisms per 100 ml, and the Total Streptococcus is more than 240 colonies per 100 ml). Monitoring confirms the contamination of these wells from septic tanks and that it was moving into groundwater, which makes it unfit for drinking due to the pathogenic germs. This poses a major problem for public health. This study has identified the effects of septic tank effluent on groundwater quality in this area.

The aim of the study was to assess the clogging time according to several decisive parameters and conditions. Mathematical model describing solids' accumulation and decomposition in a soil filter as a function of time and, for example, total suspended solids (TSS) load in septic tank effluent (STE) was presented. The calculation procedure was based on the Kozeny-Carman equation. The experimental results of the hydraulic gradient were used to estimate the infiltration velocity. The empirical data of TSS concentrations in STE were taken from the literature and own study. The analyses of the factors affecting the time of clogging of the soil infiltration system (TSS concentration, biomass density, hydraulic load, clogging layer depth) were shown. Besides the decisive factors of clogging such as TSS concentration, water content and distribution of solids in the vertical cross-section of the filter were identified also as important factors. Due to the fact that the only controllable factor is the concentration of the suspension, one should strive to use highly efficient septic tanks or polishing systems in order to obtain the lowest possible concentrations of total suspended solids in the wastewater entering the soil drainage system. [ABSTRACT FROM AUTHOR]

The aim of the study was to describe in a mathematical manner the hydraulic capacity of textile filters for wastewater treatment at changeable wastewater levels during a period between consecutive doses, taking into consideration the decisive factors for flow-conditions of filtering media. Highly changeable and slightly changeable flow-conditions tests were performed on reactors equipped with non-woven geo-textile filters. Hydraulic conductivity of filter material coupons was determined. The dry mass covering the surface and contained in internal space of filtering material was then indicated and a mathematical model was elaborated. Flow characteristics during the highly changeable flow-condition test were sensitivity to differentiated values of hydraulic conductivity in horizontal zones of filtering layer. During the slightly changeable flow-conditions experiment the differences in permeability and hydraulic conductivity of different filter (horizontal zones) height regions were much smaller. The proposed modelling approach in spite of its simplicity provides a satisfactory agreement with empirical data and therefore enables to simulate the hydraulic capacity of vertically oriented textile filters. The mathematical model reflects the significant impact of the filter characteristics (textile permeability at different filter height) and operational conditions (dosing frequency) on the textile filters hydraulic capacity.

Septic tank effluent contains high organic and nutrient contents. This study aimed to evaluate treatment performance of an algal-bacterial photobioreactor (AB-PBR) treating the septic tank effluent. The experimental unit employed a transparent plastic medium made from recycled drinking water bottles for attached-growth biofilm. Red LED lamp (light intensity ~100 μmol/m²/s) was applied as an energy source for the growth of algal-bacterial biofilm in the AB-PBR. The experimental results showed that AB-PBR operated at the hydraulic retention time (HRT) of 3 days gave the highest chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal efficiencies of 64, 45 and 35%, respectively, by which the effluent COD concentrations could meet the effluent standards of Thailand, but the effluent TN and TP concentrations needed to be further removed. The Stover-Kincannon model was applied to determine the kinetic values of COD and TN removals with R² values greater than 0.8. Microbiological examinations indicated Chlorella sp. is the predominant algal species growing in the AB-PBR, while the amplicon sequencing information analytical results revealed the bacterial phylum of Proteobacteria to be the predominant bacterial group. [ABSTRACT FROM AUTHOR]

Wetlands now days apply as a polishing system for the classical wastewater treatment, in addition of different usages. Usually wetland systems are inexpensive methods vs. expensive high technology treatment systems. Objective of this study is an evaluation of natural wetland treatment in polishing of a septic effluent. Research duration works extended for 10 months on a natural wetland system in Pardis of Mazandaran University of medical sciences and eastern north of health faculty. Wastewater quality index such as pH, EC, BOD, COD, TSS, Nitrate, Phosphorus, Ammonia and Temperature performed on the samples of influent and effluent of the system. The study showed the system works as a buffering system for flow and pH. Results indicated that average of BOD5 and TSS efficiency were 67.70and 83%, respectively. Efficiency of COD was 65.26 and 80 % for a Low and moderate strength influent respectively. Average of phosphorus, NH3 and Nitrate in effluent were 0.032 mg/L, 7.18 and 0.036 mg/L, respectively. Efficiency of ammonia and Phosphorus were slightly increased in best condition. Based on this study result, natural wetland can be success in BOD, COD, and TSS removal of the classical septic tank, but for nitrogen and Phosphorus removal do not have considerable effects.

This study investigates the wastewater treatment performance of four local plant species in wetland roof systems (WRs). The tested species include Cyperus Javanicus Hot (WR1), Eleusine Indica (L.) Gaertn (WR2), StruchiumSparganophorum (L.) Kuntze (WR3) and Kyllinga Brevifolia Rottb (WR4). The plant growth rate, nutrient uptake, wastewater treatment performance and leaf coverage were investigated. The WRs were operated at hydraulic loading rates of 353–403 m 3 ha −1 day −1 . As a result, WR4 achieved the highest biomass growth of 73.7 g day −1 (fresh weight) or 12.0 g day −1 (dry weight). The nutrient accumulation of WR4, according to dry biomass, was 1.7% of total nitrogen (TN) and 0.05% of total phosphorus (TP). The highest COD and TN removal rates (33 ± 10 kg COD ha −1 day −1 and 14 ± 4 kg TN ha −1 day −1 , respectively) were also recorded in WR4. There was statistically insignificant difference in TP removal rates (0.4–0.5 kg ha −1 day −1 ) among WRs. In terms of green leaf area coverage, WR1 and WR4 also introduced extremely high specific green leaf area as 98 and 99 m 2 of green leaves per m 2 of wetland area, respectively. Subsequently, WR1 and WR4 performed better than others in a range of benefits providing green area and treating septic tank effluent. [ABSTRACT FROM AUTHOR]

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13 million people (about 20% of the population) use on-site wastewater treatment in France. Buried vertical sand filters are often built, especially when the soil permeability is not sufficient for septic tank effluent infiltration in undisturbed soil. Clogging is one of the main problems deteriorating the operation of vertical flow filters for wastewater treatment. The extent of clogging is not easily assessed, especially in buried vertical flow sand filters. We suggest examining two possible ways of detecting early clogging: (1) NH 4 –N/NO 3 –N outlet concentration ratio, and (2) oxygen measurement within the porous media. Two pilot-scale filters were equipped with probes for oxygen concentration measurements and samples were taken at different depths for pollutant characterization. Influent and effluent grab-samples were taken three times a week. The systems were operated using batch-feeding of septic tank effluent. Qualitative description of oxygen transfer processes under unclogged and clogged conditions is presented. NH 4 –N outlet concentration appears to be useless for early clogging detection. However, NO 3 –N outlet concentration and oxygen content allows us to diagnose the early clogging of the system. [ABSTRACT FROM AUTHOR]

Small point sources of pollutants such as septic tanks are recognised as significant contributors to streams' pathogen and nutrient loadings, however there is little data in the UK on which to judge the potential risks that septic tank effluents (STEs) pose to water quality and human health. We present the first comprehensive analysis of STE to help assess multi-pollutant characteristics, management-related risk factors and potential tracers that might be used to identify STE sources. Thirty-two septic tank effluents from residential households located in North East of Scotland were sampled along with adjacent stream waters. Biological, physical, chemical and fluorescence characterisation was coupled with information on system age, design, type of tank, tank management and number of users. Biological characterisation revealed that total coliforms and Escherichia coli ( E. coli ) concentration ranges were: 10 3 –10 8 and 10 3 –10 7 MPN/100 mL, respectively. Physical parameters such as electrical conductivity, turbidity and alkalinity ranged 160–1730 μS/cm, 8–916 NTU and 15–698 mg/L, respectively. Effluent total phosphorus (TP), soluble reactive P (SRP), total nitrogen (TN) and ammonium-N (NH 4 –N) concentrations ranged 1–32, < 1–26, 11–146 and 2–144 mg/L, respectively. Positive correlations were obtained between phosphorus, sodium, potassium, barium, copper and aluminium. Domestic STE may pose pollution risks particularly for NH 4 –N, dissolved P, SRP, copper, dissolved N, and potassium since enrichment factors were > 1651, 213, 176, 63, 14 and 8 times that of stream waters, respectively. Fluorescence characterisation revealed the presence of tryptophan peak in the effluent and downstream waters but not detected upstream from the source. Tank condition, management and number of users had influenced effluent quality that can pose a direct risk to stream waters as multiple points of pollutants. [ABSTRACT FROM AUTHOR]

Three new baffle flow constructed wetlands (CWs), namely the baffle horizontal flow CW (Z1), baffle vertical flow CW (Z2) and baffle hybrid flow CW (Z3), along with one traditional horizontal subsurface flow CW (Z4) were designed to test the removal efficiency of nitrogen (N) and phosphorus (P) from the septic tank effluent under varying hydraulic retention times (HRTs). Results showed that the optimal HRT was two days for maximal removal of N and P from the septic tank effluent among the four CWs. At this HRT, the Z1, Z2, Z3 and Z4 CWs removed, respectively, 49.93, 58.50, 46.01 and 44.44% of TN as well as 87.82, 93.23, 95.97 and 91.30% of TP. Our study further revealed that the Z3 CW was the best design for overall removal of N and P from the septic tank effluent due to its hybrid flow directions with better oxygen supply inside the CW system. [ABSTRACT FROM AUTHOR]

While 95 percent of the U.S. experience with drip dispersal is outside New England, national experience dates back more than 20 years and covers areas of the country with comparable climatic conditions. The number and type of such systems recently installed in New England is presented along with present cost data to illustrate those situations in which drip dispersal may be cost-effective compared to other land-based effluent disposal systems. Drip dispersal is not always cost-effective, but several design aspects help the practitioner to identify cost savings. [ABSTRACT FROM AUTHOR]

Performance of the laboratory-scale recycled rubber particles (RRP) biofilter was compared to a conventional gravel system and a peat biofilter for treatment of septic tank effluent. During the study, the RRP biofilter provided similar or better performance than other systems in terms of organic removal and hydraulic capacity. After the start-up period, RRP biofilter achieved removal efficiencies for BOD5, total suspended solids (TSS), ammonia nitrogen of 96%, 93%, and 90%, respectively, over the range of hydraulic loading rates of 57–204 L/m2/d. On the other hand, the peat biofilter failed hydraulically and the gravel system showed high TSS concentrations in the effluent. RRP provided high surface area and sufficient time for biological treatment. In addition, RRP was observed to provide ammonia adsorption capacity. The results showed that RRP has the potential to be used as substitutes for natural aggregate such as gravel in septic system drainfields. The RRP biofilter can be used as alternative septic systems for the sites where an existing septic system has failed or site conditions, such as high groundwater table or small lot size, are not suitable for the installation of conventional septic systems. [ABSTRACT FROM AUTHOR]

In this paper, the preliminary study on the impact of filamentous particles (FP) in the septic tank effluent (STE) on filter cake (FC) development was presented. The number, length and diameter (30 p./cm3, 451 and 121 μm, respectively, on average) of FPs were measured using microscope image analysis of STE samples condensed using a vacuum evaporation set. Results of this study showed, that 0.73% of volatile suspended solids (VSSs) mass from the STE occurs in the form of FPs. No correlation between FP total mass and VSS was found. An experiment with a layer of FPs simulated by ground toilet paper was conducted and showed the impact of this layer (4.89 mg/cm2) on wastewater hydraulic conductivity – for an FC with FPs (FC–FP), hydraulic conductivity was seven times lower than for the FC without the FP layer, and on outflow quality (lower concentration of organic matter expressed as chemical oxygen demand (COD) in effluent from the FC–FP filter than in the effluent from the FC filter: 618 and 732 gO2/m3, respectively). Despite a relatively small amount of FPs in STE solids (as volume fraction), they play an important role in FC development due to their relatively high length and low degradability. Probably relatively small pores of the FC containing FPs (FC–FP) caused a small particle blocking and a decrease in permeability. [ABSTRACT FROM PUBLISHER]

Abstract: An extensive field study on percolation areas receiving both septic tank and secondary treated on-site effluents from single houses in Ireland was carried out to investigate the attenuation capacity of highly permeable subsoils with respect to E. coli bacteria and spiked bacteriophages (MS2, ΦX174 and PR772). The development of biomats across the percolation areas receiving the secondary effluent was restricted compared to the percolation area receiving septic tank effluent, promoting a much higher areal hydraulic loading which created significant differences in the potential microbiological loading to groundwater. Greatest E. coli removal in the subsoil occurred within the first 0.35m of unsaturated subsoil for all effluent types. Analysis showed, however, that more evidence of faecal contamination occurred at depth in the subsoils receiving secondary treated effluents than that receiving septic tank effluent, despite the lower bacterial influent load. All three bacteriophages were reduced to their minimum detection limit (<10PFU/mL) at a depth of 0.95m below the percolation trenches receiving septic tank effluent, although isolated incidences of ΦX174 and PR772 were measured below one trench. However again, slightly higher breakthroughs of MS2 and PR772 contamination were detected at the same depth under the trenches receiving secondary treated effluent. [Copyright &y& Elsevier]

Although groundwater quality depends on microbial processes in the soil treatment area (STA) of onsite wastewater treatment systems (OWTS), our understanding of the development of these microbial communities is limited. We examined the bacterial communities of sand, sandy loam, and clay STAs at different depths in response to septic tank effluent (STE) addition using mesocosms. Terminal restriction fragment length polymorphism (TRFLP) analysis was used to compare the bacterial community structure and composition of STE, native soil prior to STE addition (UNX) and soil exposed to STE (EXP). Principal component analysis separated communities with depth in sand but not in sandy loam or clay. Indices of richness, diversity, and evenness followed the order: sandy loam > sand > clay. Analysis of TRF peaks indicated that STE contributed least to the composition of STA bacterial communities (5%-16%), followed by UNX soil (18%-48%), with the highest proportion of the community made up of TRFs not detected previously in either UNX or STE (50%-82%) for all three soils. Soil type and depth can have a marked effect on the structure and composition of STA bacterial communities, and on the relative contribution of native soil and STE to these communities. [ABSTRACT FROM AUTHOR]

Two species of earthworms, Lumbricus terrestris and Eisenia fetida, were used to de-clog sand filters purifying domestic sewage. The experimental set-up consisted of 6 filtration columns (4 research filters and 2 control filters) filled with fine sand (d60 =0.2 mm, d10 =0.1 mm). The sewage parameters at inflow to the filters were typical of the septic tank effluent. The filters were fed about 5.5 dm³/day at average doses of 31 cm/d. The TSS cumulative loading after three months was equal to 931.9 g/m². At the start of filter operating the average outflow of filters was equal to 105.6 cm³ /min; at the end (except for filter Nos. 2 and 6) it was 0.3 cm /min per filter and the clogging was achieved. A significant increase in outflow rates was observed two weeks after the application of worms, and it was equal to 94.7±2.9 cm³/min on average (average value for control filters: 7.1±0.8). The content of organic matter in the clogging layer of filters 4 and 5 was equal to 9.6±0.5 mg of dry mass per 1 g of sand, on average, and was significantly lower than the content of organic matter in the clogging layer of control filters (28.2±1.0 mg dry mass per 1 g of sand). There was no difference between control and research filter treatment efficiency (COD and NH4 -N). Four months after the worm application, the increase in average outflow from research filters was still observed, thus the de-clogging effect had been observed as long as the worms were alive. [ABSTRACT FROM AUTHOR]

Soil columns were set up to survey the bacterial community in the soil for septic tank effluent treatment. When bio-clogging occurred in the soil columns, the effluent from the columns was in poorer quality. To evaluate changes of the soil bacterial community in response to bio-clogging, the bacterial community was characterized by DNA gene sequences from soil samples after polymerase chain reaction coupled with denaturing gradient gel electrophoresis process. Correspondence analysis showed that Proteobacteria related bacteria were the main bacteria within the soil when treating septic tank effluent. However, Betaproteobacteria related bacteria were the dominant microorganisms in the normal soil, whereas Alphaproteobacteria related bacteria were more abundant in the clogged soil. This study provided insight into changes of the soil bacterial community in response to bio-clogging. The results can supply some useful information for the design and management of soil infiltration systems. [ABSTRACT FROM AUTHOR]

We tested intermittent aeration of the soil treatment area (STA) of onsite wastewater treatment systems (OWTS) for its ability to restore and maintain STA hydraulic flow and improve the water quality functions of conventional OWTS. Evaluation was conducted on hydraulically-failed conventional OWTS at three state-owned medical group homes in Washington County, RI, USA. Testing was conducted in two phases, with Phase I (before intermittent soil aeration (ISA)) comprising the first 6 months of the study, and Phase II (during ISA) the remaining 7 months. Intermittent soil aeration restored STA hydraulic function in all three systems despite a marked reduction in the STA total infiltrative surface. Soil pore water was collected from 30 and 90 cm below the STA during both phases and analyzed for standard wastewater parameters. Although the STA infiltrative surface was reduced-and the contaminant load per unit of area increased-after installation of the ISA system, no differences were observed between phases in concentration of total N, NO3, total P, or dissolved organic carbon (DOC). Apparent removal rates-which do not account for dilution or differences in infiltrative area-for total N, total P, and DOC remained the same or improved during Phase II relative to the pre-operation phase. Furthermore, intermittent soil aeration enhanced actual removal rates -which do account for dilution and differences in infiltrative area. The effects of ISA on actual removal of contaminants from STE increased with increasing hydraulic load-a counterintuitive phenomenon, but one that has been previously observed in laboratory studies. The results of our study suggest that intermittent soil aeration can restore and maintain hydraulic flow in the STA and enhance carbon and nutrient removal in conventional OWTS. [ABSTRACT FROM AUTHOR]

Results of carbon and nitrogen removal by moving bed biological reactors operating in two modes - continuous flow and sequencing batch - are presented. Three hybrid reactors with intermittent aeration were simultaneously operated in laboratory. Real septic tank effluent from a household was treated. The research confirmed satisfactory removal of carbon and nitrogen (up to 88% and 64%, respectively) by the hybrid reactors. The most preferable conditions for carbon and nitrogen removal were: hydraulic retention time = 0.55 d with 15/15 minutes aeration/non-aeration intervals in continuous flow reactors and four-hour cycles in sequencing batch reactors. Higher COD loadings on reactors' volumes induced higher biomasses of biofilm and lower concentrations of activated sludge, but sludge wastage was negligible. Various groups of organisms were observed in both - activated sludge flocks and biofilm. The highest concentration of filamentous microorganisms was observed in the reactor with the highest COD loading. Rotifers were much more abundant in biofilm than in flocks, due to their relatively long growth time. [ABSTRACT FROM AUTHOR]

A constructed wetland-pond system consisting of two free-water-surface-flow (FWS) wetland cells, a scenic pond, and a slag filter in series was used for reclamation of septic tank effluent from a campus building. The results show that FWS wetlands effectively removed major pollutants under a hydraulic loading rate between 2.1 and 4.2 cm/d, with average efficiencies ranging from 74 to 78% tot total suspended solids, 73 to 88% for 5-day biochemical oxygen demand, 42 to 40% for total nitrogen, 34 to 70% for total phosphorous, 64 to 79% for total coliforms, and 90 to 99.9% for Escherichia coli. After passing through the scenic pond and slag filter, the reclaimed water was used for landscape irrigation. There were a variety of ornamental plants and aquatic animals established in the second FWS cell and scenic pond with good water quality, thus enhancing landscape and ecology amenity in campuses. [ABSTRACT FROM AUTHOR]

The integrated wetland systems were constructed by combining horizontal-flow and vertical-flow bed, and their purification efficiencies for septic tank effluent were detected when the hydraulic retention time (HRT) was 1 d, 3 d, 5 d under different seasons. The results showed that the removal efficiencies of the organics, phosphorus were steady in the hybrid systems, but the removal efficiency of total nitrogen was not steady due to high total nitrogen concentration in the septic tank effluent. The average removal rates of COD (chemical oxygen demand) were 89%, 87%, 83%, and 86% in summer, autumn, winter and spring, respectively, and it was up to 88%, 85%, 73%, and 74% for BOD_5 (5 d biochemical oxygen demand) removal rate in four seasons. The average removal rates of TP (total phosphorous) could reach up to 97%, 98%, 95%, 98% in four seasons, but the removal rate of TN (total nitrogen) was very low. The results of this study also indicated that the capability of purification was the worst in winter. Cultivating with plants could improve the treated effluent quality from the hybrid systems. The results of the operation of the horizontal-flow and vertical-flow cells (hybrid systems) showed that the removal efficiencies of the organics, TP and TN in horizontal-flow and vertical-flow cells were improved significantly with the extension of HRT under the same season. The removal rate of 3 d HRT was obviously higher than that of 1 d HRT, and the removal rate of 5 d HRT was better than that of 3 d HRT, but the removal efficiency was not very obvious with the increment of HRT. Therefore, 3 d HRT might be recommended in the actual operation of the hybrid systems for economic and technical reasons. [ABSTRACT FROM AUTHOR]

A systematic kinetic study of phosphorus (P) sorption by various materials in the soil infiltration system of septic tanks was undertaken by following the time course of P sorption by sorbents in contact with various P solutions over periods up to 360 days. Uptake of P seemed to consist of two distinct stages. Initial uptake was very rapid and this phase was completed in 4 days or less. A slower removal stage followed for some materials over many months. Phosphorus sorption during the fast reaction stage appeared to be associated with the soluble Ca content of the materials. The fast reaction of calcareous materials accounted for the bulk (>70%) of the total P removed. Merribrook loamy sand exhibited the highest proportion of P sorption during the slow phase. It should be noted, however, that for solution P concentrations in the range found in typical effluents (∼ ∼20 mg L−1) the fast reaction phase seemed to be responsible for virtually all P removed. None of the six kinetic formulae examined possessed the sophistication and detail needed to portray accurately the time course of P sorption for all the sorbents investigated. The Elovich equation and the kinetic modification of the Freundlich isotherm expression appeared to provide a reasonable fit of the experimental data. [ABSTRACT FROM AUTHOR]

Fly ash has been found to be a potential material for the treatment of municipal and industrial wastewater, and may be useful in the treatment of septic tank effluent. Laboratory columns (30 cm) were used to determine the sorption capacity and hydraulic properties of lagoon fly ash, loamy sand, sand, and sand amended by lagoon fly ash (30 and 60%) and red mud gypsum (20%). The removal of chemical oxygen demand (COD) was high in all column effluents (71–93%). Extent of nitrification was high in Spearwood sand, Merribrook loamy sand and 20% red mud gypsum amended Spearwood sand. However, actual removal of nitrogen (N) was high in columns containing lagoon fly ash. Unamended Spearwood sand possessed only minimal capacity for P sorption. Merribrook loamy sand and red mud gypsum amended sand affected complete P removal throughout the study period of 12 weeks. Significant P leakage occurred from lagoon fly ash amended sand columns following 6–10 weeks of operation. Neither lagoon fly ash nor red mud gypsum caused any studied heavy metal contamination including manganese (Mn), lead (Pb), zinc (Zn), cadmium (Cd) and chromium (Cr) of effluent. It can be concluded that Merribrook loamy sand is better natural soil than Spearwood sand as a filter medium. The addition of lagoon fly ash enhanced the removal of P in Spearwood sand but the efficiency was lower than with red mud gypsum amendment. [ABSTRACT FROM AUTHOR]

Decentralized wastewater treatment systems enable wastewater to be treated at the source for cleaner discharge into the environment, protecting public health while allowing for reuse for agricultural and other purposes. This study, conducted in Thailand, investigated a decentralized wastewater treatment system incorporating a physical and photochemical process. Domestic wastewater from a university campus and conventional septic tank effluent from a small community were filtered through a woven-fiber microfiltration (WFMF) membrane as pretreatment for ultraviolet (UV) disinfection. In domestic wastewater, WFMF reduced TSS (by 79.8%), turbidity (76.5%), COD (38.5%), and NO3 (41.4%), meeting Thailand irrigation standards for every parameter except BOD. In septic tank effluent, it did not meet Thailand irrigation standards, but reduced TSS (by 77.9%), COD (37.6%), and TKN (13.5%). Bacteria (total coliform and Escherichia coli) and viruses (MS2 bacteriophage) passing through the membrane were disinfected by flow-through UV reactors containing either a low-pressure mercury lamp or light-emitting diodes (LEDs) emitting an average peak wavelength of 276 nm. Despite challenging and variable water quality conditions (2% < UVT < 88%), disinfection was predictable across water types and flow rates for both UV sources using combined variable modeling, which enabled us to estimate log inactivation of other microorganisms. Following UV disinfection, wastewater quality met the WHO standards for unrestricted irrigation. [ABSTRACT FROM AUTHOR]

Attached-growth photobioreactors (AG-PBRs) employing low-cost attached-growth media were applied to treat septic tank effluent which contained abundant organic and nutrient matters as well as pathogenic microorganisms. This study investigated effects of blue and red LED lights on organic, nutrient and pathogenic removals, biomass productivity and compositions of microbial community in the AG-PBR system. The experimental results showed the blue AG-PBR to be more effective in removing chemical oxygen demand (COD), total nitrogen (TN) and ammonia nitrogen (NH 3 –N) and generating biomass productivity than those of the red AG-PBR (P < 0.05). Mass balance analysis indicated that the TN and total phosphorus (TP) were removed mainly by assimilation into the biomass. The TN removal rates via nitrification and denitrification processes in the blue AG-PBR were found to be higher than that of the red AG-PBR, corresponding to the observed results of bacterial biomass and abundances of nitrifying and denitrifying bacterial species in the treatment systems. The maximal areal algal biomass productivity of 47 gDW/(m2. d) in the blue AG-PBRs was found to be higher than those of other algal attached-growth systems. Although, the red and blue AG-PBR systems could effectively treat the septic tank effluent to meet the national and international discharge standards, based on treatment efficiencies and biomass productivity, the blue AG-PBR is recommended for treatment of septic tank effluent. Image 1 • The attached-growth photobioreactors (AG-PBRs) could treat septic tank effluent. • Specific wavelengths of light had effects on the performance of the AG-PBRs. • The blue AG-PBR performed highest treatment efficiencies and biomass productivity. • Nutrients in septic tank effluent could be recovered via the biomass assimilation. [ABSTRACT FROM AUTHOR]

This work presents preliminary results from two constructed wetlandsfor municipal wastewater treatment in Estonia: (1) a free water surface constructed wetland (a cascade of 4 serpentine ponds in which Typha latifolia and Phragmites australis have been planted (total area about 1.2 ha, mean depth of the ponds 0,5 m) for secondary treatment of waste water from the town of Poltsamaa with about 5,000 inhabitantsand from a food processing factory, and (2) a two-chamber horizontal-flow sand-plant filter (two chambers, 30x 6.25x 1.0 m, each) filled with coarse sand, one planted with Typha latifolia, and the other with Iris pseudacorus and Phragmites australis, receiving a septic tank effluent of about 40 population equivalents in Kodijarve. The horizontal flow sand-plant filter showed satisfactory purification efficiency in terms of BOD7 and phosphorus (66-95% and 63-96%, respectively). However, nitrogen removal was relatively low, varying from 12 to 85%.In the cascade of free water surface wetlands, the most critical parameter is phosphorus retention. Mean purification efficiency observedwas about 73% for nitrogen, 68% for BOD7 and 24% for phosphorus. Purification efficiency in both wetland systems did not decrease during the cold season. [ABSTRACT FROM AUTHOR]