Intermittent Sand Filtration Research Articles

Combined coagulation and intermittent sand filtration for on-site treatment of greywater

Performance of coagulation followed by intermittent saturated sand filtration system was evaluated for greywater treatment using real greywater. Filters with two different grain sizes were used to study the effect of media size on the removal. Filters were charged daily with 20 L of greywater coagulated with polyaluminium chloride (PACl). Performance of the filters were evaluated based on physicochemical and microbial parameters. Results showed that coagulation followed by sand filtration resulted in 94, 76 and 80% reduction in turbidity, BOD and COD respectively. Also, more than 99% of total and faecal coliform removal was observed. Sand filter with smaller grain size performed significantly better than the sand filter with coarser grain size. Coagulation followed by filtration showed stable and reliable performance as the effluent quality was insensitive to fluctuations in influent quality. Combined coagulation and sand filtration produced effluent conforming to different reuse standards.

Performance evaluation of two filter materials in intermittent sand filtration system

The environment is a treasure that needs to be protected from point and diffuse sources of pollution. Most wastewater treatment plants cannot attain 100% efficiencies and this call for tertiary treatment process before discharging final treated wastewater into the environment. The study focused on harnessing the locally available materials, sand and granulated Palm Kernel Shell (gPKS) as filters for treatment of wastewater from constructed wetland using intermittent filtration system in the laboratory. The filter depth and hydraulic loading rate was 650 mm and 0.135 L min-1, respectively. Applied wastewater was effluent from the Constructed Wetland (CW) of wastewater treatment plant University of Lagos. The filtration system was dosed intermittently 6 hourly for 12 weeks. Experimental results showed that pH of the effluent from gPKS filter medium was slightly reduced to the influent due to acidic nature of the gPKS while effluent from sand filter slightly increased. The five day biochemical oxygen demand (BOD5) removal efficiency for the gPKS and sand filters were 59.2 and 69.08% respectively, while the corresponding average Dissolve Oxygen (DO) were 2.9 ± 0.6 mg L-1 and 3.4 ± 0.345. The percentage removal of E. coli in sand and gPKS filters are 69.34% and 87.49% respectively.

Treatment of domestic greywater by geotextile filter and intermittent sand filtration bioreactor

Intermittent sand filtration (ISF) is an efficient system for treatment of greywater; however, the high quality of effluent and the simple set-up contrast with the high failure rate due to clogging of surface layers. The efficacy of several polypropylene non-woven geotextiles (apparent opening size from 0.10 to 0.18 mm) used as primary treatment filters to remove suspended particles from domestic greywater and the effects of this pretreatment in the performance of fine and small media size (0.3 and 0.6 mm) ISFs was examined. Results showed geotextile achieved suspended solids (SS) removal rates from 25 to 85% and chemical oxygen demand (COD) from 3 to 30%; although the portion larger than 75 μm was removed at higher rates (55–90%), particles smaller than the nominal pore size of the filter were also captured. Geotextile used as pretreatment resulted in improvement of lifetime of the ISFs over an experimental run of 60 days. The vertical profile of volatile organic matter in the ISFs was evaluated at the end of the experiment and it showed a clear reduction in the accumulation of organic material on the top layer of the ISFs, effectively avoiding its early failure by accumulation of solids.

REVIEW ON NATURAL METHODS FOR WASTE WATER TREATMENT

In Ethiopia, the most common method of disposal of waste water is by land spreading. This treatment method has numerous problems, namely high labor requirements and the potential for eutrophication of surface and ground waters. Constructed wetlands are commonly used for treatment of secondary municipal wastewaters and they have been gaining popularity for treatment of agricultural wastewaters in Ethiopia. Intermittent sand filtration may offer an alternative to traditional treatment methods. As well as providing comparable treatment performance, they also have a smaller footprint, due to the substantially higher organic loading rates that may be applied to their surfaces. This paper discusses the performance and design criteria of constructed wetlands for the treatment of domestic and agricultural wastewater, and sand filters for the treatment of domestic wastewater. It also proposes sand filtration as an alternative treatment mechanism for agricultural wastewater and suggests design guidelines.

REVIEW ON NATURAL METHODS FOR WASTE WATER TREATMENT

In Ethiopia, the most common method of disposal of waste water is by land spreading. This treatment method has numerous problems, namely high labor requirements and the potential for eutrophication of surface and ground waters. Constructed wetlands are commonly used for treatment of secondary municipal wastewaters and they have been gaining popularity for treatment of agricultural wastewaters in Ethiopia. Intermittent sand filtration may offer an alternative to traditional treatment methods. As well as providing comparable treatment performance, they also have a smaller footprint, due to the substantially higher organic loading rates that may be applied to their surfaces. This paper discusses the performance and design criteria of constructed wetlands for the treatment of domestic and agricultural wastewater, and sand filters for the treatment of domestic wastewater. It also proposes sand filtration as an alternative treatment mechanism for agricultural wastewater and suggests design guidelines.

Depth and performance evaluation of a laboratory scale sand filtration system for wastewater treatment

Intermittent sand filtration (ISF) was adopted in the treatment of synthetic wastewater having septic tank effluent's properties in the laboratory. Over a period of 84 days synthetic wastewater was intermittently dosed onto two sand filters of 50 cm and 100 cm depths at an interval of 4 h. The filter material has an effective size d$_{10}$ of 0.42 mm, d$_{60}$ of 0.92 mm, coefficient of uniformity, Cu, of 2.2, and hydraulic conductivity of 4.632 $\times $ 10$^{-3\, }$ms$^{-1}$ with an effective pore diameter of 0.094 mm. The hydraulic loading was 0.144 m/day and the BOD$_{5}$ of the wastewater was 172.3 mg/L. The removal of suspended solids, ammonium-nitrogen (NH$_{4}$-N), and BOD$_{5}$ in 100- and 50-cm columns was 91.4% and 88.6%, 98.7% and 99.8%, and 92% and 90%, respectively, while PO$_{4}$-P removal was about 45% in both columns. Unlike other parameters, NO$_{3}$-N was increasing, which signifies that denitrification did not take place in the filter columns. Based on the results, the filter column of 50 cm is economically preferable due to the insignificant difference when compared with the 100-cm filter column. The bacteria removal was slightly higher in 100 cm depth (99.88%) than in 50 cm depth (99.68%).

Simulation of water flow and solute transport in intermittent sand filter

Research Article| February 01 2012 Simulation of water flow and solute transport in intermittent sand filter Mahmoud Bali; Mahmoud Bali 1Department of Geology, Faculty of Sciences, Tunis, Tunisia E-mail: mahmoud.bali@yahoo.fr Search for other works by this author on: This Site PubMed Google Scholar Moncef Gueddari Moncef Gueddari 1Department of Geology, Faculty of Sciences, Tunis, Tunisia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2012) 61 (1): 50–57. https://doi.org/10.2166/aqua.2012.104 Article history Received: December 25 2010 Accepted: November 15 2011 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Mahmoud Bali, Moncef Gueddari; Simulation of water flow and solute transport in intermittent sand filter. Journal of Water Supply: Research and Technology-Aqua 1 February 2012; 61 (1): 50–57. doi: https://doi.org/10.2166/aqua.2012.104 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Water and solute transport in intermittent sand filtration was simulated with a modified HYDRUS 1D program. Field trials were performed through a 10 × 10 m infiltration basin located at Dissa agriculture area in the north of Gabes city (south-east Tunisia). Performance of the calibrated model has been statistically evaluated for its ability to predict water flow and solute transport. Comparisons between measured and simulated water content resulted in R2 and root mean square error (RMSE) average values of 0.88 and 0.74 cm3 cm−3 for the calibration period and of 0.86 and 0.78 cm3 cm−3 for the validation period, respectively. Predicted water quality parameters were found to be in best agreement with the measured results. On average, the model predicted COD and NH4-N concentrations well, with a RMSE of 1.06 and 1.26 mg L−1 respectively. However, it underestimated NO3-N concentration. Similar corresponding values were computed for the validation period indicating that the model is able to predict water flow and solute transport with a reasonable degree of accuracy. intermittent sand filtration, simulation, treatment, wastewater This content is only available as a PDF. © IWA Publishing 2012 You do not currently have access to this content.

Bacterial, viral and turbidity removal by intermittent slow sand filtration for household use in developing countries: Experimental investigation and modeling

A two-factor three-block experimental design was developed to permit rigorous evaluation and modeling of the main effects and interactions of sand size ( d 10 of 0.17 and 0.52 mm) and hydraulic head (10, 20, and 30 cm) on removal of fecal coliform (FC) bacteria, MS2 bacteriophage virus, and turbidity, under two batch operating modes (‘long’ and ‘short’) in intermittent slow sand filters (ISSFs). Long operation involved an overnight pause time between feeding of two successive 20 L batches (16 h average batch residence time (RT)). Short operation involved no pause between two 20 L batch feeds (5 h average batch RT). Conditions tested were representative of those encountered in developing country field settings. Over a ten week period, the 18 experimental filters were fed river water augmented with wastewater (influent turbidity of 5.4–58.6 NTU) and maintained with the wet harrowing method. Linear mixed modeling allowed systematic estimates of the independent marginal effects of each independent variable on each performance outcome of interest while controlling for the effects of variations in a batch’s actual residence time, days since maintenance, and influent turbidity. This is the first study in which simultaneous measurement of bacteria, viruses and turbidity removal at the batch level over an extended duration has been undertaken with a large number of replicate units to permit rigorous modeling of ISSF performance variability within and across a range of likely filter design configurations and operating conditions. On average, the experimental filters removed 1.40 log fecal coliform CFU (SD 0.40 log, N = 249), 0.54 log MS2 PFU (SD 0.42 log, N = 245) and 89.0 percent turbidity (SD 6.9 percent, N = 263). Effluent turbidity averaged 1.24 NTU (SD 0.53 NTU, N = 263) and always remained below 3 NTU. Under the best performing design configuration and operating mode (fine sand, 10 cm head, long operation, initial HLR of 0.01–0.03 m/h), mean 1.82 log removal of bacteria (98.5%) and mean 0.94 log removal of MS2 viruses (88.5%) were achieved. Results point to new recommendations regarding filter design, manufacture, and operation for implementing ISSFs in local settings in developing countries. Sand size emerged as a critical design factor on performance. A single layer of river sand used in this investigation demonstrated removals comparable to those reported for 2 layers of crushed sand. Pause time and increased residence time each emerged as highly beneficial for improving removal performance on all four outcomes. A relatively large and significant negative effect of influent turbidity on MS2 viral removal in the ISSF was measured in parallel with a much smaller weaker positive effect of influent turbidity on FC bacterial removal. Disturbance of the schmutzdecke by wet harrowing showed no effect on virus removal and a modest reductive effect on the bacterial and turbidity removal as measured 7 days or more after the disturbance. For existing coarse sand ISSFs, this research indicates that a reduction in batch feed volume, effectively reducing the operating head and increasing the pore:batch volume ratio, could improve their removal performance by increasing batch residence time.

Wetland treatment of leachate from a closed landfill

A wetland system has operated seasonally at Saginaw Township, MI, USA, for ten years. The system consists of extraction, aeration, settling, intermittent vertical sand filtration, a surface flow wetland treatment with recycle, and discharge to the Tittibawassee River. The 0.85 ha cattail wetland treats the full leachate flow, with a total system detention time of 180 days. The high recycle rate creates a lesser wetland detention time of 60 days. Ammonia is the principal contaminant of concern, because it occurs at high concentrations, typically 300–500 mg/L. Ammonia mass reduction averaged 99.5% for the last nine years, with a 95% mass removal in the startup year. Metals were not present in all samples, with modest reductions in those always present (zinc 16%, arsenic 29%, barium 78%, chromium 67%). Volatile organic compounds were removed to below detection, excepting BTEX, which occurred in only 2% of the outflow samples. Base neutral organics, PCBs and pesticides were also removed to below detection, excepting phthalates with an outlet detection frequency of 29%. No pesticides or PCBs were detected in the system outflow. The ammonia removal rate coefficients for the wetland (12 m/yr) was at the 55th percentile of the distribution for other surface flow wetlands. The vertical filter was likely oxygen limited, and functioned with an apparent oxygen utilization of 30 gO/(m 2 d).

Intermittent slow sand filtration for preventing diarrhoea among children in Kenyan households using unimproved water sources: randomized controlled trial

Measure effectiveness of intermittent slow sand filtration for reducing child diarrhoea among households using unimproved water sources in rural Kenya. A randomized controlled trail was conducted among populations meeting a high-risk profile for child diarrhoea from drinking river water in the River Njoro watershed. Intervention households (30) were provided the concrete BioSand Filter and instructed on filter use and maintenance. Control households (29) continued normal practices. Longitudinal monthly monitoring of diarrhoea (seven-day daily prevalence recall) and of influent, effluent, and drinking water quality for fecal coliform was conducted for 6 months. Intervention households had better drinking water quality than control households (fecal coliform geometric mean, 30.0 CFU vs. 89.0 CFU/100 ml, P < 0.001) and reported significantly fewer diarrhoea days (86 days over 626 child-weeks) compared to controls (203 days over 558 child-weeks) among children up to 15 (age-adjusted RR 0.46; 95 % CI = 0.22, 0.96). Greater child diarrhoea reduction due to the intervention (age-adjusted RR 0.23, 95 % CI = 0.10, 0.51) was observed among the sub-group using unimproved water sources all of the time. Intermittent slow sand filtration, a non-commercial technology, produces similar observed effects on child diarrhoea as commercial POU products, adding to the range of effective options for poor populations (chlorination, ceramic filtration, solar disinfection, flocculation/disinfection).

Novel Hybrid Filter for the Treatment of Septic Tank Effluent

Intermittent sand filtration is a common and effective method for treating septic tank effluent. However, if the loading rate is too high, clogging and ponding of the sand filter surface layer can occur due to the accumulation of excessive biomass and the deposition of suspended solids. This ponding limits the practicality of sand filtration as it makes it necessary to take the filter out of service for maintenance. The objective of this study was to develop and test, on-site, a new hybrid filter system that would reduce the risk of clogging at an organic loading rate substantially greater than the maximum recommended loading rate for intermittent sand filters. The system comprised a 0.6 m deep horizontal flow biofilm reactor (HFBR) over a 0.85 m deep stratified sand filter. The HFBR consisted of a stack of 20 horizontal corrugated polyvinyl chloride sheets, at 32 mm vertical spacings. The sheets were arranged so that the wastewater flowed over and back along alternate sheets down through the stack. The m...

Organic carbon removal and nitrification of high strength wastewaters using stratified sand filters

The current practice of spray irrigation of dairy parlour wastewaters is laborious and time consuming. Intermittent sand filtration systems may offer an alternative to spray irrigation when designed to remove organic carbon, nitrogen, phosphorus, coliforms and viruses from such wastewaters to allow discharge of the final effluent directly into receiving waters without damage to the environment. In this study two instrumented stratified sand filter columns (0.425 and 0.9 m deep, and both 0.3 m in diameter) were intermittently loaded for 439 days with synthetic dairy parlour washings at a number of hydraulic and organic loading rates. At a biochemical oxygen demand (BOD) loading of 22 g m −2 d −1, over 92% of the BOD and suspended solids in the wastewater was removed in the two filters and nitrification was complete. The 0.9 m column had a sustained ability to adsorb the influent phosphorus during the study period; however, the phosphorus adsorption capacity of the 0.425 m column began to decrease after approximately 30 days. Biomass, comprising hydrated extracellular polymers (exopolymers) and living and dead cells, accumulated in the 0.9 m column; it was assessed by sodium bromide tracer studies and by variations in the sand volumetric water contents using time domain reflectometry (TDR). The biomass growth increased the retention time of the wastewater in the filter media, and occurred mainly at the top of the first sand layer. Intermittent stratified sand filters appear to offer an effective and sustainable treatment process for the removal of BOD from high-strength wastewaters, and for the complete nitrification of ammonium.

Intermittent sand filtration for wastewater treatment in rural areas of the Middle East - a pilot study

This paper concentrates on Intermittent Sand Filtration (ISF) as a polishing stage for effluent from a facultative pond. During the three-year research program, the system operated with an influent flow-rate of 500-1,000 L/day and an average BOD concentration of 200-400 hydraulic and BOD loadings of 110-200 L/m2/day and 20-40 gBOD/m2/day, respectively. Flow to the ISF was applied intermittently with a different number of doses in each run. In addition, the effects of the frequency and the duration of rest periods (no feeding) were studied. Removal of 90-95% of BOD and 75-90% of COD and TSS was achieved consistently throughout the study period. Elevated levels of nitrification were observed with 95-100% removal of NH3. The ISF performed best when fed with 5-10 doses/day. Reducing the daily number of doses to 3/day at the same hydraulic loading rate resulted in a 20-30% reduction in removal efficiency. The 2-4 week rest period had no effect on the biological activity in the subsequent run. However, rest periods of more than 30 days were found to negatively affect removal efficiency.

Recirculating sand filters for treatment of synthetic dairy parlor washings.

Land-spreading and spray irrigation are the most widely used practices for the disposal of dairy wastewaters in Ireland but in some cases there can be problems due to contamination of surface and ground water. The use of intermittent sand filtration has been suggested as an alternative treatment process. However, a single pass through a sand filter limits denitrification because of the absence of reducing conditions following nitrification and the lack of an available carbon source. This leads to poor total nitrogen (TN) reduction and an effluent that is high in nitrate nitrogen (NO3-N). This paper follows a previous paper in which two instrumented stratified sand filter columns (0.9 and 0.425 m deep, and both 0.3 m in diameter) were intermittently loaded with synthetic dairy parlor washings at a number of hydraulic loading rates, leading to a TN reduction of 27 to 41%. In the present study, under a chemical oxygen demand (COD) of 23.4 g m(-2) d(-1), the TN was reduced by 83.2% when three-quarters of the sand filter effluent was recirculated through an anoxic zone. This produced an effluent NO3-N concentration of 60 mg L(-1). With recirculation, the improvement in the removal of organic matter and ammonia N (NH4-N) is minimal. Recirculating sand filters appear to offer a mechanically simple and effective method for the removal of nitrogen from dairy parlor effluents and are a significant improvement over a single-pass sand filter.

Recirculating Sand Filters for Treatment of Synthetic Dairy Parlor Washings

Land-spreading and spray irrigation are the most widely used practices for the disposal of dairy wastewaters in Ireland but in some cases there can be problems due to contamination of surface and ground water. The use of intermittent sand filtration has been suggested as an alternative treatment process. However, a single pass through a sand filter limits denitrification because of the absence of reducing conditions following nitrification and the lack of an available carbon source. This leads to poor total nitrogen (TN) reduction and an effluent that is high in nitrate nitrogen (NO3–N). This paper follows a previous paper in which two instrumented stratified sand filter columns (0.9 and 0.425 m deep, and both 0.3 m in diameter) were intermittently loaded with synthetic dairy parlor washings at a number of hydraulic loading rates, leading to a TN reduction of 27 to 41%. In the present study, under a chemical oxygen demand (COD) of 23.4 g m−2 d−1, the TN was reduced by 83.2% when three-quarters of the sand filter effluent was recirculated through an anoxic zone. This produced an effluent NO3–N concentration of 60 mg L−1 With recirculation, the improvement in the removal of organic matter and ammonia N (NH4–N) is minimal. Recirculating sand filters appear to offer a mechanically simple and effective method for the removal of nitrogen from dairy parlor effluents and are a significant improvement over a single-pass sand filter.

Intermittent Sand Filtration for Domestic Wastewater Treatment: Effects of Filter Depth and Hydraulic Parameters

Intermittent sand filtration for wastewater treatment is an established technology that has attracted renewed interest due to its potential to satisfy many of the current needs for wastewater treatment in unsewered areas. While some sand filter systems have demonstrated excellent performance, the complex relations between the many variables that affect performance are not understood well enough to allow optimized design. Nine pilot scale septic tank-sand filter pairs were constructed and operated for a period of 10 months to examine the effects of media depth, hydraulic conductivity, and infiltration rate on the performance of intermittent sand filters for treating domestic wastewater. Three media depths ranging from 0.30 to 0.60 m (0.98 to 1.97 ft) were selected for the study and performance of the filters was evaluated based on current discharge standards for BOD5, suspended solids, and ammonia-nitrogen in Ohio. Filter depth clearly has an important influence on the quality of treatment. Measurement of hydraulic parameters was useful, but results were difficult to correlate with treatment performance. The experimental system designed for this research has extensive capabilities for investigating relations between operational variables and filter performance. Future research needs for intermittent sand filtration systems are suggested.

Upgrading effluent quality for lagoon-based systems

To establish Best Available Technology Economically Achievable (BATEA) in non-urban communities which presently use conventional lagoon technology, an investigation was undertaken to evaluate alternatives which can be used to improve lagoon effluent and establish costs. Evaluated were the “Sutton” and the intermittent sand filtration or “New Hamburg” processes. The Sutton concept consists of a nitrifying extended-aeration plant followed by polishing lagoons, with waste sludge discharged into the lagoons. The New Hamburg concept consists of aerated or facultative lagoons, with the lagoon effluent sprayed intermittently over sand filters. The Sutton plants produce an improved effluent quality relative to conventional facultative lagoons in terms of BOD5 and TSS concentrations. Increases in ammonia concentration across the polishing pond occur after 5-7 years of plant operation, suggesting a need to implement a regular program of sludge removal from the lagoon. The New Hamburg process results in a significant improvement in effluent quality in terms of BOD5, TSS, TP, TKN, NH3-N and H2S concentrations. Approximate capital costs for upgrading the existing conventional lagoons in Ontario to Sutton and New Hamburg process facilities are estimated at US $221 million and US $93 million, respectively.

Upgrading effluent quality for lagoon-based systems

To establish Best Available Technology Economically Achievable (BATEA) in non-urban communities which presently use conventional lagoon technology, an investigation was undertaken to evaluate alternatives which can be used to improve lagoon effluent and establish costs. Evaluated were the “Sutton” and the intermittent sand filtration or “New Hamburg” processes. The Sutton concept consists of a nitrifying extended-aeration plant followed by polishing lagoons, with waste sludge discharged into the lagoons. The New Hamburg concept consists of aerated or facultative lagoons, with the lagoon effluent sprayed intermittently over sand filters.The Sutton plants produce an improved effluent quality relative to conventional facultative lagoons in terms of BOD5 and TSS concentrations. Increases in ammonia concentration across the polishing pond occur after 5–7 years of plant operation, suggesting a need to implement a regular program of sludge removal from the lagoon. The New Hamburg process results in a significant improvement in effluent quality in terms of BOD5, TSS, TP, TKN, NH3-N and H2S concentrations. Approximate capital costs for upgrading the existing conventional lagoons in Ontario to Sutton and New Hamburg process facilities are estimated at US $221 million and US $93 million, respectively.

A filtration technique for algal removal from lagoon effluents

ABSTRACT: As part of a comprehensive evaluation of posttreatment techniques for algal removal from lagoon effluents, intermittent sand filtration was evaluated. The main objective of the study was to delineate the filtration process most feasible for upgrading lagoons and to identify optimum design and operating parameters. Experimental procedures were conducted at the site of Starkville, Mississippi's 6.1‐hectare (15‐acre) lagoon. Studies utilized a full‐scale sonic microstrainer supplied by FMC Corporation and pilot‐sized rapid and intermittent sand filters. Microstraining was characterized by low specific flow rates and poor effluent quality. Rapid sand filters were unable to produce desirable effluent quality in conjunction with a sufficient filter run length. Intermittent sand filters were capable of consistently producing an effluent quality comparable to those expected from more complex advanced waste treatment processes. Optimum media gradation and hydraulic loading for the intermittent sand filters were determined. This paper presents the results of the intermittent sand filter studies.

Alternative Approaches for Upgrading Effluent Quality for Lagoon Based Systems

The province of Ontario is Canada's most populous province with over 8 million residents out of a total population of 27 million. The province has 512 sewage treatment plants of which 137 or 27% are lagoons. Improved environmental effluent quality standards since the introduction of the lagoons has resulted in many of these being unable to achieve proper effluent quality. Typical effluent quality requirements across the province require a minimum of secondary treatment, that is 15 mg/l of BOD and suspended solids and 1 mg/l of total phosphorus. The movement towards a clean environment has resulted in phosphorus levels as low as 0.3 mg/l TP and in an increasing number of cases, full nitrification year round. Because many of these lagoons serve small populations in the 100 - 3 000 population equivalents category, the cost of upgrading such lagoons to tertiary quality effluent is significant. Two approaches for upgrading conventional lagoon systems were evaluated. They are called the Sutton and New Hamburg processes after the towns in Ontario where they were first installed. The Sutton process consists of extended aeration plant, followed by polishing lagoons with waste sludge sent directly to the lagoons, while the New Hamburg process consists of conventional lagoons followed by intermittent sand filtration.