On-site Treatment Systems Research Articles

Adaptable improved onsite wastewater treatment systems for urban settlements in developing countries

Onsite sanitation is widely adopted in developing countries. Septic tanks being one of the onsite treatment systems is still adopted and scaled up especially in urban settlements. But, experience s...

Field testing of a household-scale onsite blackwater treatment system in South Africa

Innovations that enable cost-effective and resource-conserving treatment of human waste are required for the 4.2 billion people in the world who currently lack safe and reliable sanitation services. Onsite treatment and reuse of blackwater is one strategy towards this end, greatly reducing the need to transport wastewater over long distances either via sewers or trucks. Here, we report on the field testing of a prototype onsite blackwater treatment system conducted over a period of 8 months. The system was connected to a women's toilet in a public communal ablution block located in an informal settlement near Durban, South Africa. Liquid waste was treated by separation and diversion of large solids, settling of suspended solids, and filtration through activated carbon prior to disinfection by electrochemical oxidation. System performance was monitored daily by measurement of chemical and physical water quality parameters onsite and confirmed by periodic detailed analysis of chemical and biological parameters at an offsite lab. Daily monitoring of system performance indicated that the effluent had minimal color and turbidity (maximum 90 Pt/Co units and 6.48 NTU, respectively), and consistent evolution of chlorine as blackwater passed through the system. Weekly offsite analysis confirmed that the system consistently inactivated pathogens (E. coli and coliforms) and reduced chemical oxygen demand and total suspended solids to meet ISO 30500 category B standards. Significant reductions in total nitrogen load were also observed, though these reductions often fell short of the 70% reduction required by ISO 30500. No significant reduction in total phosphorus was observed. Maintenance requirements were identified, and the resilience of the system to restart following a prolonged shutdown was demonstrated, but significant improvements are required in the design of the solid/liquid separation mechanism for application of this system in a wiping culture.

Digested blackwater treatment in a partial nitritation-anammox reactor under repeated starvation and reactivation periods

Abstract Wastewater source-separation and on-site treatment systems face severe problems in wastewater availability. Therefore, the effect of repeated short-term starvation and reactivation periods on a partial nitritation-anammox (PN/AMX) based processes were assessed treating digested blackwater at room temperature. Two sequencing batch reactors (SBR) were operated, one of them during 24 h/day the whole week (SBR-C, which served as control) and the other with repeated starvation/reactivation periods during the nights and the weekends (SBR-D), using simulated blackwater (300 mg N/L and 200 mg COD/L) as substrate. Results showed no remarkable differences in overall processes performance between both reactors, achieving total nitrogen removal efficiencies (NRE) around 90%. Furthermore, no significant variations were measured in specific activities, except for the aerobic heterotrophic one that was lower in SBR-D, presumably due to the exposure to anoxic conditions. Then, the technical feasibility of applying the PN/AMX system to treat real blackwater produced in an office building during working hours was successfully proved in a third reactor (SBR-R), with the same starvation/reactivation periods tested in SBR-D. Despite the low temperature, ranging from 14 to 21 °C, total NRE up to 95% and total nitrogen concentration in the effluent lower than 10 mg N/L were achieved. Moreover, the PN/AMX process performance was immediately recovered after a long starvation period of 15 days (simulating holidays). Results proved for the first time the feasibility and long-term stability (100 days) of applying the PN/AMX processes for the treatment (and potential reuse) of blackwater in a decentralized system where wastewater is not always available.

Wastewater management in urban Bhutan: Assessing the current practices and challenges

This study reviews the current wastewater management practices and their challenges in urban Bhutan. The study data was collected from the local authorities of 35 classified towns, and the field survey was conducted for the two representative towns of Thimphu City and Khuruthang town. The study observed that only eight of the 35 classified towns (22.8%) have public sewerage systems, with an average coverage of 19.7% of Bhutan’s total urban population, or 7.4% of Bhutan’s entire population. The imported modular wastewater treatment technology was significantly more expensive than alternative options; however, approximately six towns have already adopted this technology, due to a lack of space for a much cheaper waste stabilisation ponds. Currently, over 80% of Bhutan’s urban population depends on the on-site sanitation system for their domestic wastewater disposal; however, over 40% of these properties lacked a soak-pit system for the safe disposal of septic tank effluent. Therefore, this study indicates that urban settlements in Bhutan are potentially subjected to overflow of significant amount of hazardous septic tank effluents directly into the environment posing significant risk to public and the environment. A critical urban plot space analysis indicates that the current system of on-site sanitation is inadequate and unsuitable for the current urban settings. Since it is impractical for the government to provide public sewerage system to all the towns, a low-cost public sewerage system, or an alternative and improved on-site treatment system, needs to be explored and promoted to achieve long-term environmental objectives.

Beyond signal quality: The value of unmaintained pH, dissolved oxygen, and oxidation-reduction potential sensors for remote performance monitoring of on-site sequencing batch reactors

Sensor maintenance is time-consuming and is a bottleneck for monitoring on-site wastewater treatment systems. Hence, we compare maintained and unmaintained sensors to monitor the biological performance of a small-scale sequencing batch reactor (SBR). The sensor types are ion-selective pH, optical dissolved oxygen (DO), and oxidation-reduction potential (ORP) with platinum electrode. We created soft sensors using engineered features: ammonium valley for pH, oxidation ramp for DO, and nitrite ramp for the ORP. Four soft sensors based on unmaintained pH sensors correctly identified the completion of the ammonium oxidation (89–91 out of 107 cycles), about as many times as soft sensors based on a maintained pH sensor (91 out of 107 cycles). In contrast, the DO soft sensor using data from a maintained sensor showed slightly better (89 out of 96 cycles) detection performance than that using data from two unmaintained sensors (77, respectively 82 out of 96 correct). Furthermore, the DO soft sensor using maintained data is much less sensitive to the optimisation of cut-off frequency and slope tolerance than the soft sensor using unmaintained data. The nitrite ramp provided no useful information on the state of nitrite oxidation, so no comparison of maintained and unmaintained ORP sensors was possible in this case. We identified two hurdles when designing soft sensors for unmaintained sensors: i) Sensors’ type- and design-specific deterioration affects performance. ii) Feature engineering for soft sensors is sensor type specific, and the outcome is strongly influenced by operational parameters such as the aeration rate. In summary, the results with the provided soft sensors show that frequent sensor maintenance is not necessarily needed to monitor the performance of SBRs. Without sensor maintenance monitoring small-scale SBRs becomes practicable, which could improve the reliability of unstaffed on-site treatment systems substantially.

Design, installation, operation and experimentation of septic tank – UASB wastewater treatment system

The project intends to design, fabricate and test a highrate anaerobic reactor that can treat the domestic wastewater and produce biogas as a byproduct. The biogas is a combustible mixture of methane, carbon monoxide, hydrogen gases etc. and can be used in the table burner. The target of the biogas reactor is to treat the wastewater generate from domestic wastewater at Kathmandu University. The major outcome of this project is to be a working design of the biogas digester which can be fabricated and can be coupled with domestic septic for the domestic wastewater treatment. The septic tank uses as a primary treatment of the wastewater whereas UASB is taken as a secondary treatment. We design pilot scale UASB wastewater treatment system and test know the proper operation of the reactor. The septic tank-UASB combine system has TSS and CODt removal efficiency of 83% and 88% respectively. This system is one of the appropriate systems for onsite wastewater treatment in the developing country.

Modelling Phosphorus Sorption Kinetics and the Longevity of Reactive Filter Materials Used for On-Site Wastewater Treatment

Use of reactive filter media (RFM) is an emerging technology in small-scale wastewater treatment to improve phosphorus (P) removal and filter material longevity for making this technology sustainable. In this study, long-term sorption kinetics and the spatial dynamics of sorbed P distribution were simulated in replaceable P-filter bags filled with 700 L of reactive material and used in real on-site treatment systems. The input data for model calibration were obtained in laboratory trials with Filtralite P®, Polonite® and Top16. The P concentration breakthrough threshold value was set at an effluent/influent (C/C0) ratio of 1 and simulations were performed with P concentrations varying from 1 to 25 mg L−1. The simulation results showed that influent P concentration was important for the breakthrough and longevity, and that Polonite performed best, followed by Top16 and Filtralite P. A 100-day break in simulated intermittent flow allowed the materials to recover, which for Polonite involved slight retardation of P saturation. The simulated spatial distribution of P accumulated in the filter bags showed large differences between the filter materials. The modelling insights from this study can be applied in design and operation of on-site treatment systems using reactive filter materials.

Designing green walls for greywater treatment: The role of plants and operational factors on nutrient removal

Green walls, installed on the side of the buildings, mainly for their aesthetics and micro climate benefits, could become effective on-site greywater treatment solutions. However, far more research is needed to convert these nature-based systems into low-cost water purification technologies. This process study presents the first step in development of greywater-treating green walls by examining how variation in plant spaces and operational conditions (hydraulic loading rate, inflow concentrations and intermittent drying) influence nutrient removal from light greywater. The experiment was conducted over 12 months on a large-scale pilot green wall located in a laboratory in Melbourne, Australia. The results showed that ornamental plant species can successfully adapt to greywater only irrigation regime and play an important role in nitrogen and phosphorus uptake from greywater. Higher performing plants, C. appressa, N. obliterate, M. parvifolium and L. muscari, had on average 7–10% higher TN removal than unvegetated configuration (over 88% removal overall), which is attributed to consistently high NOx uptake. On the other hand, poorer performing plants O. japonicus, P. occidentalis and N. officinale tended to leach NOx, likely due to their shallow or slow developing root systems. While low retention times hindered high TP removal from all tested configurations, high dependency on plant species and operational conditions was still observed, with C. appressa and N. obliterata being the two highest performing plants (34–53% removal during standard operation). The overall phosphorus uptake was found to improve over time, suggesting that plant growth is a significant TP removal mechanism in green walls. While drying caused a performance drop for all designs, higher performing plant species were less affected by changes in operational conditions. The tested configurations showed good resilience to sudden inflow concentration increases, suggesting green walls could be used as a robust and aesthetically attractive on-site greywater treatment system.

On-site treated wastewater disposal systems – The role of stratified filter medias for reducing the risk of pollution

The transmission of pathogens from partially or fully treated wastewater to different water sources are a pervasive risk to public health. To reduce the risk, the integration of source separation, on-site greywater treatment system, and an efficient disposal scheme are the most critical approaches. This study intended to evaluate the removal of nutrient and microbial suspension in the filtration systems used for effluent disposal. The effluent from an on-site greywater treatment plant was loaded into the columns, and the effluent from the columns was monitored for nutrients, total coliform bacteria, Escherichia coli, and Salmonella typhimurium phage 28B (St28B) for one year. Thus, from the range of infiltration systems tested, column-B (15 cm layer of each, Filtralite, fine sand, and till soil) showed the highest removal of total coliforms and E. coli, 3–4 log10 reduction, while the lowest removal observed in column-C (a layer of 25 cm crushed stone and 50 cm till soil), 2–3 log10 reduction. The virus removal efficiency of the columns reduced from 19% to 70% during the simulation of a rainfall event. Moreover, the rise of St28B concentration after rainfall experiment may probably the sign of detachment enhanced by low ionic strength rainwater.

Removal of Phosphorus from Domestic Wastewater in Actual On-site Treatment Systems using Phosphorus Removal Pellets

Removal of Phosphorus from Domestic Wastewater in Actual On-site Treatment Systems using Phosphorus Removal Pellets

Concentrations of pharmaceuticals and other micropollutants in groundwater downgradient from large on-site wastewater discharges.

Large subsurface treatment systems (LSTS) and rapid infiltration basins (RIB) are preferred onsite wastewater treatments compared to direct discharge of treated wastewater to streams and adjacent facilities. Discharge of these wastewater treatments may result in contaminant loading to aquifers that also serve as drinking water sources downgradient from the discharge site. Until recently, few studies have characterized the contribution of micropollutants (e.g. pharmaceuticals, fragrances, flame retardants, etc.) to receiving aquifers. We conducted a pilot project to characterize the occurrence of micropollutants in groundwater downgradient from 7 on-site treatment systems in Minnesota, USA: 5 community LSTS and 2 municipal RIB. One downgradient monitoring well was sampled three times at each facility over one year. Of 223 micropollutants analyzed, 35 were detected. Total sample concentrations ranged from 90 to 4,039 ng/L. Sulfamethoxazole (antibiotic) was detected in all samples at concentrations from 7 to 965 ng/L. Other pharmaceuticals (0.12–1,000 ng/L), organophosphorus flame retardants (10–500 ng/L), and other anthropogenic chemicals (4–775 ng/L) were also detected. The numbers and concentrations of micropollutants detected were inversely related to dissolved oxygen and depth to water. Ratios of pharmaceutical concentrations to human-health screening values were <0.10 for most samples. However, concentrations of carbamazepine and sulfamethoxazole exceeded screening values at two sites. Study results illustrate that large on-site wastewater systems designed to discharge to permeable soil or shallow groundwater effectively deliver pharmaceuticals and other micropollutants to groundwater aquifers and could contribute micropollutants to drinking water via water supply wells.

RABBIT’S HEALTH AND ENVIRONMENTAL IMPACTS OF EXPLOITATION TREATED BIODEGRADABLE POLLUTION WATER BY JOHKASOU SYSTEM

This paper is considered as a part of a multi-disciplinary analysis “Application of Decentralized On-Site Water Treatment System in Egypt for Use in Agriculture and Producing Safe Animal Proteins”. The project aimed to investigate the environmental impact of implementing sewage water before and after treatment using the effluent of the on-site decentralized Japanese’ Johkasou system. Blood chemistry of liver and kidney enzymes revealed significant increase in the fourth week in comparison with groups of treated and tap water. On the other hand, ALT and AST levels have no statistical differences between treated and tap water reared animals. The progressive pathological lesions were noted in 100% and 70% untreated water groups.The benefit of Johkasou system model CE10 in treatment of sewage water and suitability for rearing of animals is demonstrated.

Simulated discharge of treated landfill leachates reveals a fueled development of antibiotic resistance in receiving tidal river

Around 350 million tons of solid waste is disposed of in landfills every year globally, with millions of cubic meters of landfill leachates released into neighboring environment. However, to date, little is known about the variations of antimicrobial resistance (AMR) in on-site leachate treatment systems and its development in leachate-receiving water environment. Here, we quantified 7 subtypes of antibiotic resistance genes (ARGs), 3 types of culturable antibiotic resistant bacteria (ARB) and 6 subtypes of mobile genetic elements (MGEs) in the effluents from a combined leachate treatment process, including biological treatment (MBR), physical separation (UF), ultraviolet (UV) disinfection and advanced oxidation process (AOP). The contents of ARGs, ARB and MGEs were generally enriched by the MBR, but then decreased significantly along with the tertiary treatment process. However, in the effluent-receiving water samples, the abundance of dominant ARGs (i.e. ermB, sul1, blaTEM) increased by 1.5 orders of magnitude within 96 h, alongside a general increase of MGEs (~10.0 log10(copies/mL) and total ARB (~1100 CFU/mL). Structural correlation analyses reveal that target ARGs were closely associated with MGEs, particularly in effluent-receiving samples (Procrustes test; M2 = 0.49, R = 0.71, P = 0.001); and occurrences of ARB were majorly affected by ARG's distribution and environmental conditions (e.g. nitrogen speciation) in effluent and recipient groups, respectively. This study indicates that current treatment technologies and operation protocols are not feasible in countering the development of AMR in effluent-receiving water environment, particularly in tidal rivers that are capable of retaining contaminants for a long residence time.

Phosphorus reduction in filters for on-site wastewater treatment

Discharges of phosphorus (P) from on-site wastewater treatment systems generally contribute to eutrophication problems in Swedish freshwaters and, ultimately, in the Baltic Sea. Such concerns have led to a growing interest in improving P removal in treatment facilities. This study investigated the reduction of P in 12 full-scale on-site treatment systems featuring sand filters and alkaline P-filters by sampling and analysing filter influents and effluents. The flow-proportional samples collected were analysed for total and dissolved P, BOD7, total and dissolved organic carbon (TOC and DOC), and pH. Seven of the eight investigated sand filters did not provide satisfactory total P reduction; the likely explanations are filter clogging and wastewater dilution by extraneous water. In addition, effluents from four of the eight sand filters had total P concentrations higher than 3 mg L−1, which is the Swedish effluent limit recommended for common receiving waters, indicating that a subsequent polishing step would be needed. Six of the nine investigated P-filters reduced P adequately, with total P concentrations in the effluent ranging between 0.1 and 1.9 mg L−1. The three underperforming P-filters had effluent pH values below 9; filter age, clogging, and hydraulic overload were identified as probable reasons for their poor performance. A statistically significant correlation was found between total-P reduction and filtrate pH, but no significant correlation was detected between organic load in the influent and P reduction by the P-filters. The P-filter media replacement frequency could not be established, but filtrate pH appeared to be a good estimator.

Small Water Enterprise in Rural Rwanda: Business Development and Year-One Performance Evaluation of Nine Water Kiosks at Health Care Facilities.

Small water enterprises (SWEs) have lower capital expenditures than centralized systems, offering decentralized solutions for rural markets. This study evaluated SWEs in rural Rwanda, where nine health care facilities (HCF) owned and operated water kiosks supplying water from onsite water treatment systems (WTS). SWEs were monitored for 12 months. Spearman’s Rank Correlation Coefficient (rs) was used to evaluate correlations between demand for kiosk water and community characteristics, and between kiosk profit and factors influencing the cost model. On average, SWEs distributed 15,300 L/month. One SWE ran at a loss, four had profit margins of ≤10% and four had profit margins of 45–75%. Factors influencing SWE performance were intermittent water supply (87% of SWE closures were due to water shortage), consumer demand (demand was high where populations already used improved water sources (rs = 0.81, p = 0.02)), price sensitivity (demand was lower where SWEs had high prices (rs = −0.65, p = 0.08)), and production cost (water utility tariffs negatively impacted SWE profits (rs = −0.52, p < 0.01)). Sustainability was more favorable in circumstances where recovery of capital expenditures was not expected, and the demand for treated water was sufficient to fund operational expenditures. Future research is needed to assess the extent to which kiosk revenue can support ongoing operational costs of WTS and kiosks both at HCF and in other contexts.

Septic systems contribute to nutrient pollution and harmful algal blooms in the St. Lucie Estuary, Southeast Florida, USA

Nutrient enrichment is a significant global-scale driver of change in coastal waters, contributing to an array of problems in coastal ecosystems. The St. Lucie Estuary (SLE) in southeast Florida has received national attention as a result of its poor water quality (elevated nutrient concentrations and fecal bacteria counts), recurring toxic Microcystis aeruginosa blooms, and its proximity to the northern boundary of tropical coral species in the United States. The SLE has an artificially large watershed comprised of a network of drainage canals, one of which (C-44) is used to lower the water level in Lake Okeechobee. Public attention has primarily been directed at nutrient inputs originating from the lake, but recent concern over the importance of local watershed impacts prompted a one-year watershed study designed to investigate the interactions between on-site sewage treatment and disposal systems (OSTDS or septic systems), groundwaters, and surface waters in the SLE and nearshore reefs. Results provided multiple lines of evidence of OSTDS contamination of the SLE and its watershed: 1) dissolved nutrients in groundwaters and surface waters were most concentrated adjacent to two older (pre-1978) residential communities and the primary canals, and 2) sucralose was present in groundwater at residential sites (up to 32.0μg/L) and adjacent surface waters (up to 5.5μg/L), and 3) δ15N values in surface water (+7.5 o/oo), macroalgae (+4.4 o/oo) and phytoplankton (+5.0 o/oo) were within the published range (>+3 o/oo) for sewage N and similar to values in OSTDS-contaminated groundwaters. Measured δ15N values in M. aeruginosa became increasingly enriched during transport from the C-44 canal (∼5.8 o/oo) into the mid-estuary (∼8.0 o/oo), indicating uptake and growth on sewage N sources within the urbanized estuary. Consequently, there is a need to reduce N and P loading, as well as fecal loading, from the SLE watershed via septic-to-sewer conversion projects and to minimize the frequency and intensity of the releases from Lake Okeechobee to the SLE via additional water storage north of the lake. These enhancements would improve water quality in both the SLE and Lake Okeechobee, reduce the occurrence of toxic harmful algal blooms in the linked systems, and improve overall ecosystem health in the SLE and downstream reefs.

Treated Greywater Reuse for Hydroponic Lettuce Production in a Green Wall System: Quantitative Health Risk Assessment

The scarcity and pollution of freshwater are extremely crucial issues today, and the expansion of water reuse has been considered as an option to reduce its impact. This study aims to assess the efficiency of an integrated greywater treatment system and hydroponic lettuce production as a part of a green wall structure, and to evaluate the health risk associated with the production and consumption of lettuce through a quantitative microbial risk assessment (QMRA) and a chemical health risk assessment. The study was conducted based on the unique configuration of a source separation system; an on-site greywater treatment system; a green wall structure as a polishing step; and hydroponic lettuce production in the green wall structure. The final effluent from the system was used to grow three lettuce varieties by adding urine as a nutrient solution. Both water samples and plant biomass were collected and tested for Escherichia coli (E. coli) and heavy metals contamination. The system has gained a cumulative 5.1 log10 reduction of E. coli in the final effluent and no E. coli found in the plant biomass. The estimated annual infection risk for Cryptosporidium, Campylobacter, and Norovirus was 10−6–10−8, 10−8–10−10, and 10−10–10−11 respectively. These results indicate that the system attained the health-based targets, 10−6 disability adjusted life years (DALYs) per person per year. Similarly, the health risk index (HRI) and targeted hazard quotient (THQ) results did not exceed the permissible level, thus the chemical health risk concern was insignificant.

Performance study of biofilter system for on-site greywater treatment at cottages and small households

The current contribution of microbial pathogens and nutrient discharge into the environment from inefficient on-site wastewater treatment systems has raised concern in many areas due to the pollution of the nearby water recipient. To overcome this challenge, a novel and more robust proven treatment systems are required. This paper aims to assess the performance of a source separating wastewater management system for the removal of organic matter, total P, total suspended particles and E. coli. The system is a multi-stage approach including – a separate collection of blackwater (BW) and greywater, followed by on-site greywater treatment system in a fixed-film biofilter and finally a soil infiltration system used as a polishing step before discharging into the environment. The separation and collection of BW resulted a notable reduction for chemical oxidation demand (COD), biochemical oxidation demand (BOD), total suspended solids (TSS), nitrogen (N) and phosphorus (P) accounting for 64%, 61%, 75%, 85 and 88%, respectively. The overall removal efficiency of the system for the above-mentioned parameters reached over 90% at the biofilter effluent and more than 95% at the bottom of the constructed infiltration column. For coliform bacteria and E. coli, the overall system reached a reduction of 4–5 log10 units of which the major reduction was observed in the infiltration columns. The effluent quality from this source-separating and multi-barrier biofilter treatment system complies with the Norwegian discharge limits. The assessment results reveal that this system can be used in drinking water source catchments with minimum environmental and health related risks.

Total staphylococci as performance surrogate for greywater treatment

Faecal indicator bacteria (FIB) are commonly used as water quality indicators; implying faecal contamination and therefore the potential presence of pathogenic enteric bacteria, viruses, and protozoa. Hence in wastewater treatment, the most commonly used treatment process measures (surrogates) are total coliforms, faecal coliforms, Escherichia coli (E. coli), and enterococci. However, greywater potentially contains skin pathogens unrelated to faecal load, and E. coli and other FIB may grow within greywater unrelated to pathogens. Overall, FIB occurs at fluctuating and relatively low concentrations compared to other endogenous greywater bacteria affecting their ability as surrogates for pathogen reduction. Therefore, unlike municipal sewage, FIB provides a very limited and unreliable log-reduction surrogate measure for on-site greywater treatment systems. Based on our recent metagenomic study of laundry greywater, skin-associated bacteria such as Staphylococcus, Corynebacterium, and Propionibacterium spp. dominate and may result in more consistent treatment surrogates than traditional FIB. Here, we investigated various Staphylococcus spp. as potential surrogates to reliably assay over 4-log10 reduction by the final-stage UV disinfection step commonly used for on-site greywater reuse, and compare them to various FIB/phage surrogates. A collimated UV beam was used to determine the efficacy of UV inactivation (255, 265 and 285 nm) against E. coli, Enterococcus faecalis, E. faecium, E. casseliflavus, Staphylococcus aureus, and S. epidermidis. Staphylococcus spp. was estimated by combining the bi-linear dose-response curves for S. aureus and S. epidermidis and was shown to be less resistant to UV irradiation than the other surrogates examined. Hence, a relative inactivation credit is suggested; whereas, the doses required to achieve a 4 and 5-log10 reduction of Staphylococcus spp. (13.0 and 20.9 mJ cm−2, respectively) were used to determine the relative inactivation of the other microorganisms investigated. The doses required to achieve a 4 and 5-log10 reduction of Staphylococcus spp. resulted in a log10 reduction of 1.4 and 4.1 for E. coli, 0.8 and 2.8 for E. faecalis, 0.8 and 3.6 for E. casseliflavus and 0.8 and 1.2 for MS2 coliphage, respectively. Given the concentration difference of Staphylococcus spp. and FIB (3 to 5-log10 higher), we propose the use of Staphylococcus spp. as a novel endogenous performance surrogate to demonstrate greywater treatment performance given its relatively high and consistent concentration and therefore ability to demonstrate over 5-log10 reductions.

Chemical and Microbiological Quality of Effluents from Different On-Site Wastewater Treatment Systems across Finland and Sweden

Domestic wastewaters, which cannot be disposed through sewage networks, must be treated with different on-site treatment systems; these are usually commercial, small-scale treatment plants or built sand filters. These systems are usually maintained by the house’s inhabitants. This study was achieved by analysing the chemical and microbiological data of 717 effluents collected in Finland and Sweden. There were inadequate reductions in 31% of phosphorus effluents, 22% of nitrogen effluents and 5% of biological oxygen demand compounds. The addition of a coagulant capable of precipitating phosphorus improved the performance of sand filters and biorotors. There are no legally binding limitations on the number of enteric microorganisms that can be present in an effluent, but the number of Escherichia coli and enterococci exceeded more than 100 colony forming units per 100 mL in 59% and 53% effluents studied, with the highest numbers for these indicators being more than 100,000 cfu per 100 mL. The number of E. coli and enterococci were lower when the concentration of phosphorus in effluent was less than 1 mg/L. The treatment efficiency varied extensively, even between similar plant models, possibly due to either irregular use, or after long pauses, when they were not being used. In addition, it is possible that the end users are not capable of properly maintaining these wastewater treatment plants.