Waste Stabilization Pond System Research Articles

Sewage Treatment by Waste Stabilization Pond Systems

Sewage generated in Ghana is commonly discharged into the environment without any form of treatment to reduce the degree ofcontamination and mitigate potential public health and environmental issues. Although some attempts have been made in someparts of Ghana to utilize the waste stabilization pond (WSP) system to treat domestic sewage, the ponds often fail to achievetheir purpose due to lack of basic maintenance and supervision. To assess the utility of the WSP system for treating sewage,wastewater samples were collected from the raw sewage, anaerobic, facultative and maturation ponds of WSPs at Obuasi inGhana, and analyzed for physicochemical and microbiological contaminants. The results show that the final pond effluent meetsrecommended microbiological and chemical quality guidelines. The waste stabilization pond system demonstrates high removalefficiencies of wastewater contaminants. The biochemical oxygen demand, total suspended solids, nitrate and faecal coliformsreduction efficiencies of 97.3%, 97.6%, 83.3% and 99.94% respectively are highly significant, and compare well with reportedremoval efficiencies in the literature. Additionally, the ponds have high reduction efficiencies for heavy metals and pathogenicmicroorganisms. The wastewater treatment system complies with standard wastewater management practices, and provides auseful method for treating and disposing wastewater in Ghana.

Performance Evaluation of Waste Stabilisation Ponds

Waste stabilisation pond system has been used more especially in developing countries for sewage treatment. The objective of this study was to investigate the hydraulic and performance efficiency of Palapye waste stabilisation ponds. The hydraulic efficiency was evaluated through drogue, pond geometry and sludge accumulation assessment. The performance efficiency was evaluated through periodic sampling and analysis of physiochemical and bacteriological parameters of individual units and of the system as a whole. Except for the maturation ponds, the depth of the anaerobic pond had reduced from 4 m to 0.45 m, for facultative ponds from 2.0 m to a range of 0.52 m - 0.91 m. The design hydraulic retention time of the system had reduced from 20 days to 7.1 days. The concentration of some physiochemical parameters in the effluent was 305 mg·L-1, 277 Nephelometric Turbidity Units (NTU), 204 mg·L-1, 156 mg·L-1, 110 mg·L-1, and 15 mg·L-1 being total suspended solids, turbidity, nitrates, chemical oxygen demand, biochemical oxygen demand and phosphate respectively. These values were more than the standard limits of the country. Effluent total coliforms concentration was 3.6 log units and within the threshold of 4.3 log units, faecal coliforms concentration was 3.5 log units, slightly higher than the threshold of 3 log units. Though Escherichia coli have no limits for discharge into other environments, the concentration in the effluent was reasonable at 2.5 log units and also within irrigation limit of 3 log counts. Palapye wastewater treatment system hydraulic efficiency is lower than the design criterion. The system was overall poor in physiochemical parameters removal but better in bacteriological removal.

Evaluation of the Ecological Integrity and Microalgae Carbon Sequestration Potential Across the Sewage Effluent Gradient of Tropical Waste Stabilization Pond System

Evaluation of the Ecological Integrity and Microalgae Carbon Sequestration Potential Across the Sewage Effluent Gradient of Tropical Waste Stabilization Pond System

Phycoremediation: An Eco-Solution to Environmental Protection and Sustainable Remediation

Phycoremediation involves the remediation of contaminants in a water body using algae (micro and macro). Algae fix carbon-dioxide by photosynthesis and remove excess nutrients effectively at minimal cost. It removes pathogens and toxic materials from waste water. Xenobiotics, chemicals and heavy metals are known to be detoxified, transform, accumulated or volatilized by algal metabolism. It offers advantage over conventional methods of remediation by its effectiveness, efficiency and eco-friendly nature. Commercially, it involves design and construction of Waste Stabilization Pond System (WSPs) and High Rate Algal Ponds (HRAP) with difference in that WSPs are unmixed or involves a little mixing, so can experience stratification, but the HRAPs involves process of mixing using paddle wheel. There are industries that are commercially involved in phycoremediation and they experience cost reduction and maximization of profit compared to the convectional system of remediation.

Microbial removal efficiency of a natural wastewater treatment system and the impact of its effluent on receiving waters

The discharge of untreated or partially treated wastewater into streams is a huge problem in developing countries in that it leads to severe environmental degradation, and, also, poses serious public health challenges to communities which live downstream. The study investigated the microbial removal efficiency of individual ponds of a waste stabilization pond system and the overall performance of the treatment systems in the removal of indicator bacteria and organic matter. The impact of the discharged effluent on the receiving waters was evaluated. The final effluent concentration of BOD and TSS were 1.7±1.2 and 10.1±4.3 mg/l, representing overall removal efficiencies of 98.7 and 98.6 percent, respectively. Overall log removal of faecal coliform (FC) and E. coli were 3.8, and 4.7 log units, representing a percentage removal of 98.4 and 99.8 percent, respectively. The mean diversity upstream was 0.11±0.09 while the downstream was 0.14±0.05, and this was not statistically different. The presence of macro-invertebrate families of Elmidae and Libellulidae downstream the point of discharge is an indication of good water quality

Sulfur oxidation by Achromobacter xylosoxidans strain wsp05 reveals ecological widening over which thiotrophs are distributed.

Achromobacter xylosoxidans is a versatile bacterium known for its ability to degrade aromatic compounds. However, its ability to oxidize sulfur compounds for electron and energy source is not reported much. In the present work, the Gram-negative bacterium Achromobacter xylosoxidans strain wsp05 isolated from a waste stabilization ponds (WSPs) system was studied for its ability to oxidize reduced sulfur compounds. The strain was able to oxidize thiosulfate and sodium sulfite. To observe the effect of physicochemical parameters on the rate of sulfur oxidation, strain wsp05 was grown in thiosulfate (20mM) containing minimal salt medium at varied pH, temperature and ammonium and phosphate ions concentration. Maximum thiosulfate oxidation was observed at 30°C with initial pH of 7-7.2. The strain was characterized using universal 16S rRNA gene primers revealing high similarity (> 99%) with Achromobacter xylosoxidans NBRC 15126T belonging to β-proteobacteria. In the present study, we investigated the sulfur oxidation properties of the Achromobacter xylosoxidans strain wsp05, which revealed an ecological and phylogenetic widening over which the thiotrophs are distributed.

Modeling Nitrogen Dynamics in a Waste Stabilization Pond System Using Flexible Modeling Environment with MCMC.

This study presents an approach for obtaining realization sets of parameters for nitrogen removal in a pilot-scale waste stabilization pond (WSP) system. The proposed approach was designed for optimal parameterization, local sensitivity analysis, and global uncertainty analysis of a dynamic simulation model for the WSP by using the R software package Flexible Modeling Environment (R-FME) with the Markov chain Monte Carlo (MCMC) method. Additionally, generalized likelihood uncertainty estimation (GLUE) was integrated into the FME to evaluate the major parameters that affect the simulation outputs in the study WSP. Comprehensive modeling analysis was used to simulate and assess nine parameters and concentrations of ON-N, NH3-N and NO3-N. Results indicate that the integrated FME-GLUE-based model, with good Nash–Sutcliffe coefficients (0.53–0.69) and correlation coefficients (0.76–0.83), successfully simulates the concentrations of ON-N, NH3-N and NO3-N. Moreover, the Arrhenius constant was the only parameter sensitive to model performances of ON-N and NH3-N simulations. However, Nitrosomonas growth rate, the denitrification constant, and the maximum growth rate at 20 °C were sensitive to ON-N and NO3-N simulation, which was measured using global sensitivity.

Sustainable Waste Water Treatment in Developing Countries: A Case Study of IIT Kharagpur Campus

Treatment of wastewater and its reuse in irrigation and agriculture can mitigate the inevitable scarcity of safe drinking water in coming decades. For developing countries like India and especially in its under-privileged regions, it is high time to focus on sustainable wastewater treatment which will be economical and easy to construct, operate and maintain by unskilled users without much dependency on electricity. Addressing this issue, various sustainable methods of wastewater treatment was critically analyzed and the Waste Stabilization Pond system was selected. A facility was designed for 20,000 residents of Indian Institute of Technology Kharagpur campus based on its geo-climatic and wastewater characteristics. Detailed calculations were carried out to demonstrate the effluent quality with reduced BOD and E-coli is suitable for unrestricted irrigation. This project with minor customisation can act as a prototype for adjacent vast rural areas where land is available but water, electricity and skilled technicians are not. If implemented, this project will bear social benefits beyond campus such as water supply to drought prone areas, better harvest and rural employment. Moreover, it underpins government’ several initiatives to develop rural infrastructure and inclusive growth of the country.

Performance evaluation of 388 full-scale waste stabilization pond systems with seven different configurations.

Waste stabilization ponds (WSPs) and their variants are one the most widely used wastewater treatment systems in the world. However, the scarcity of systematic performance data from full-scale plants has led to challenges associated with their design. The objective of this research was to assess the performance of 388 full-scale WSP systems located in Brazil, Ecuador, Bolivia and the United States through the statistical analysis of available monitoring data. Descriptive statistics were calculated of the influent and effluent concentrations and the removal efficiencies for 5-day biochemical oxygen demand (BOD5), total suspended solids (TSS), ammonia nitrogen (N-Ammonia), and either thermotolerant coliforms (TTC) or Escherichia coli for each WSP system, leading to a broad characterization of actual treatment performance. Compliance with different water quality and system performance goals was also evaluated. The treatment plants were subdivided into seven different categories, according to their units and flowsheet. The median influent concentrations of BOD5 and TSS were 431 mg/L and 397 mg/L and the effluent concentrations varied from technology to technology, but median values were 50 mg/L and 47 mg/L, respectively. The median removal efficiencies were 85% for BOD5 and 75% for TSS. The overall removals of TTC and E. coli were 1.74 and 1.63 log10 units, respectively. Future research is needed to better understand the influence of design, operational and environmental factors on WSP system performance.

Impact of sludge layer geometry on the hydraulic performance of a waste stabilization pond

Improving the hydraulic performance of waste stabilization ponds (WSPs) is an important management strategy to not only ensure protection of public health and the environment, but also to maximize the potential reuse of valuable resources found in the treated effluent. To reuse effluent from WSPs, a better understanding of the factors that impact the hydraulic performance of the system is needed. One major factor determining the hydraulic performance of a WSP is sludge accumulation, which alters the volume of the pond. In this study, computational fluid dynamics (CFD) analysis was applied to investigate the impact of sludge layer geometry on hydraulic performance of a facultative pond, typically used in many small communities throughout the developing world. Four waste stabilization pond cases with different sludge volumes and distributions were investigated. Results indicate that sludge distribution and volume have a significant impact on wastewater treatment efficiency and capacity. Although treatment capacity is reduced with accumulation of sludge, the latter may induce a baffling effect which causes the flow to behave closer to that of plug flow reactor and thus increase treatment efficiency. In addition to sludge accumulation and distribution, the impact of water surface level is also investigated through two additional cases. Findings show that an increase in water level while keeping a constant flow rate can result in a significant decrease in the hydraulic performance by reducing the sludge baffling effect, suggesting a careful monitoring of sludge accumulation and water surface level in WSP systems.

Pathogens and fecal indicators in waste stabilization pond systems with direct reuse for irrigation: Fate and transport in water, soil and crops

Wastewater use for irrigation is expanding globally, and information about the fate and transport of pathogens in wastewater systems is needed to complete microbial risk assessments and develop policies to protect public health. The lack of maintenance for wastewater treatment facilities in low-income areas and developing countries results in sludge accumulation and compromised performance over time, creating uncertainty about the contamination of soil and crops. The fate and transport of pathogens and fecal indicators was evaluated in waste stabilization ponds with direct reuse for irrigation, using two systems in Bolivia as case studies. Results were compared with models from the literature that have been recommended for design. The removal of Escherichia coli in both systems was adequately predicted by a previously-published dispersed flow model, despite more than 10years of sludge accumulation. However, a design equation for helminth egg removal overestimated the observed removal, suggesting that this equation may not be appropriate for systems with accumulated sludge. To assess the contamination of soil and crops, ratios were calculated of the pathogen and fecal indicator concentrations in soil or on crops to their respective concentrations in irrigation water (termed soil-water and crop-water ratios). Ratios were similar within each group of microorganisms but differed between microorganism groups, and were generally below 0.1mLg−1 for coliphage, between 1 and 100mLg−1 for Giardia and Cryptosporidium, and between 100 and 1000mLg−1 for helminth eggs. This information can be used for microbial risk assessments to develop safe water reuse policies in support of the United Nations' 2030 Sustainable Development Agenda.

A comparative assessment of intensive and extensive wastewater treatment technologies for removing emerging contaminants in small communities

Ecosystem pollution due to the lack of or inefficient wastewater treatment coverage in small communities is still a matter of great concern, even in developed countries. This study assesses the seasonal performance of 4 different full-scale wastewater technologies that have been used in small communities (<2000 population equivalent) for more than 10 years in terms of emerging contaminant (EC), chemical oxygen demand (COD), total suspended solids (TSS) and NH4–N removal efficiency. The studied technologies, which were selected due to their widespread use, included two intensive treatment systems (an extended aeration system (AS) and a rotating biological contactor (RBC)) and two extensive treatment systems (a constructed wetland (CW) and a waste stabilization pond (WSP)), all located in north-eastern Spain. The studied compounds belonged to the groups of pharmaceuticals, sunscreen compounds, fragrances, antiseptics, flame retardants, surfactants, pesticides and plasticizers. The 25 ECs occurred in wastewater at concentrations ranging from undetectable to 80 μg L−1. The average removal efficiency was 42% for the CW, 62% for the AS, 63% for the RBC and 82% for the WSP. All the technologies except the WSP system showed seasonal variability in the removal of ECs. The ecotoxicological assessment study revealed that, whilst all the technologies were capable of decreasing the aquatic risk, only the WSP yielded no risk in both seasons.

Modelling antibiotics transport in a waste stabilization pond system in Tanzania

Antibiotics in wastewater have become a growing problem in urban and peri-urban areas in developing countries as a result of increased use and misuse of antibiotics. A simple dynamic model, that describes the most important removal processes of antibiotic from the wastewater stabilization pond system (WSP) “Mafisa” in Morogoro, Tanzania, was developed using STELLA® software package. The model was based on liquid chromatography tandem mass spectrometry (LCMS/MS) analysis of trimethoprim, in water collected in the WSP. Concentrations of trimethoprim measured in the dry season and the rainy season were used in development of the model. To determine the model's applicability to simulate the removal of trimethoprim, a calibration was performed using concentrations from the dry season and a validation was performed using concentrations from the rainy season. To test the model's capacity to simulate the removal of other antibiotics than trimethoprim, a second validation was performed for three other antibiotics; metronidazole, sulfamethoxazole and ciprofloxacin. A two-tailed t-test with a confidence interval of 95% showed no significant difference (P=0.7819) between the values given by the model (CSIM) and the values measured by LCMS/MS (COBS) of the first validation, and the standard deviation (SD) between the differences was 1%. The second validation gave a mean SD=18% (found by a two-tailed t-test with a confidence interval of 95%) of the differences between CSIM and COBS. The model was developed under the assumption that settling, biodegradation, hydrolysis and photolysis were the only removal processes other than outlet. The major removal processes for trimethoprim and sulfamethoxazole were through settling and the outlet. Ciprofloxacin was removed by settling in the first pond. Metronidazole was mainly removed through the outlet, but settling and hydrolysis/photolysis also played a role. A sensitivity analysis (±10%) showed that the soil adsorption coefficient, the amount of suspended matter and the ratio of flow rate and volume were the most sensitive parameters. To strengthen the model, the exact removal processes should be further analysed. To apply the model on other WSP, a calibration of the settling rate constant and the amount of suspended matter should be performed.

Performance of municipal waste stabilization ponds in the Canadian Arctic

Abstract The majority of small remote communities in the Canadian arctic territory of Nunavut utilize waste stabilization ponds (WSPs) for municipal wastewater treatment because of their relatively low capital and operational costs, and minimal complexity. New national effluent quality regulations have been implemented in Canada, but not yet applied to Canada's Arctic due to uncertainty related to the performance of current wastewater treatment systems. Waste stabilization pond (WSP) treatment performance is impacted by community water use, pond design, and climate. The greatest challenge arctic communities experience when using passive wastewater treatment technologies is the constraints imposed by the extreme climate, which is characterized as having long cold winters with short cool summers that can be solar intense. The removal of carbonaceous biochemical oxygen demand (CBOD 5 ), total suspended solids (TSS), and ammonia-nitrogen were measured during the summer treatment period (late June until early September) from 2011 to 2014 in the WSP systems of four Nunavut communities; Pond Inlet, Clyde River, Grise Fiord and Kugaaruk. Monitoring results showed that WSPs in their current single cell design can achieve greater than 80% removal of CBOD 5 and TSS but were challenged to produce effluent quality that meets secondary wastewater treatment standards ( 5 and TSS). This study points to the need for revisions of design guidelines for facultative WSPs in the Arctic, as current systems are anaerobic and do not contain sufficient dissolved oxygen required to consistently support aerobic biological treatment processes.

Occurrence of Clostridium difficile in two types of wastewater treatment plants.

Wastewater is a potential environmental source of Clostridium difficile, although a direct link with community-acquired C. difficile infection (CA-CDI) in humans has not yet been established. The present study was performed to determine the occurrence of C. difficile in two types of wastewater treatment plants (WWTPs) in Isfahan, Iran. A total of 95 samples were taken from a conventional activated sludge treatment plant and a waste stabilization ponds system, and analyzed for the presence of C. difficile. C. difficile was found in 13.6% (3/22) of digested sludge samples. However, no C. difficile was detected in inlet and outlet samples or in raw sludge of activated sludge. C. difficile was also detected in 5% (2/40) of the samples from waste stabilization ponds. Polymerase chain reaction (PCR) analysis showed that all strains of C. difficile detected were toxigenic (tcdB gene positive). This study shows that C. difficile was present in WWTPs, which might constitute a potential source of community-acquired C. difficile infection.

Role of Waste Stabilisation Ponds in the Wastewater Management

Lagooning has been a very popular technique for the treatment of wastewater. Indeed, many of the sewage treatment plants in operation are waste stabilisation pond (WSP) systems. Though most of these WSPs serve small rural communities with variety of capacity, to treat wastewater which in turn depends on the availability of land area, water - tightening costs, risk offensive smells and stricter regulations as well as insufficient technological improvements have slowed down the development of this technique. Several solutions aiming at overcoming these constraints have been implemented when retrofitting and increasing the capacity of several plants and constructing new WSP systems. This review sketches out the technological developments expected to implement in a near future.

A Review of the Mechanisms of Faecal Coliform Removal from Algal and Duckweed Waste Stabilization Pond Systems

The use of eco-technologies for wastewater treatment such as algal and duckweed-based pond systems is becoming popular in developing countries owing to its affordability and efficiency of pathogen removal in warm climates. The pathogen removal mechanisms of these treatment systems however is still not clearly understood and existing knowledge is also scattered in journals and books of different disciplines. The purpose of this paper is to provide a concise review of knowledge acquired in recent times on faecal coliform removal mechanisms in algal and duckweed ponds in a comparative way while identifying knowledge gaps that still exist. This review pays particular attention to little known removal mechanisms such as the role of algal biomass, attachment and sedimentation of faecal coliforms and the role of predation by macro-invertebrates and protozoans. Recent experiments showed that algal ponds, in comparison with duckweed ponds, are more efficient in faecal coliform removal due to the high pH and oxygenation that occur in the former and the rate of inactivation of faecal coliforms increases with increased algal biomass till a certain optimum concentration after which it decreases. This optimal algal concentration for maximum destruction of faecal coliforms can be affected by the quality and strength of the wastewater. Algae also appeared to have a destructive effect on faecal coliforms even in darkness, a phenomenon that may be the effect of toxic substances from the algae. Results also show that the role of invertebrates, particularly macro-invertebrates may be more important in duckweed pond systems. Removal of faecal coliforms through attachment and sedimentation in both duckweed and algal ponds appear to be dependent largely on concentrations of faecal coliforms present and to some extent on suspended plant and particulate matter concentrations. Wide variations in removal efficiencies were however observed. We conclude that the wide variations in removal efficiencies can be addressed by standardizing operating conditions of treatment systems. Further work is necessary to identify the substances produced by algae which appeared to be toxic to faecal coliforms as well as establishing the relative importance of predation by protozoans and macro-invertebrates in the removal of faecal coliforms.

Efficiency and design parameters of waste stabilization ponds in north-east Greece

This paper examines three waste stabilization ponds (WSP) systems located in Vamvakofito, N. Skopos and Charopo, in the Prefecture of Serres. The systems were monitored for approximately four years and design assumptions were compared to real time data. After a series of chemical, biological and microbiological analyses, their efficiency at removing SS, BOD5, COD, TN, N-NH4+, N-NO3-, TP, FC, TC, inorganic elements and heavy metals from wastewater was also estimated. Temperature and weather conditions were recorded and the suitability of the effluents for irrigation purposes was examined. Equations were derived, correlating the outflow with the inflow and the complete mix first-order reaction rate constant k20 was calculated for BOD and NOD. The assessment of the ponds’ behaviour and performance not only provides information about those specific systems, but also offers guidelines for a future design and construction of WSPs systems at regions with similar geographic characteristics.

Luxury uptake of phosphorus by microalgae in waste stabilisation ponds: current understanding and future direction

There is a need to improve phosphorus removal for the tens of thousands of small communities around the world that currently rely on waste stabilisation ponds for their wastewater treatment. We now know that microalgae in pond systems are capable of accumulating phosphorus within their cells as polyphosphate in a process known as luxury uptake, but this knowledge has not yet been applied to engineer a new process to improve phosphorus removal. This paper summarises the current understanding of this mechanism, discusses the key factors influencing polyphosphate accumulation and provides future direction for research in this field. There have only been a limited number of studies that have focussed on luxury uptake of polyphosphate by microalgae in high phosphorus concentration environments such as those found in waste stabilisation pond systems. However, from this review it has been shown that the environmental factors which influence polyphosphate storage are the phosphate concentration, light intensity and temperature. Currently we are limited to a black box understanding of the bulk population and as a result future research needs to focus on a systematic evaluation of different microalgal genera under a wide range of environmental, biological and process variables in order to reveal the conditions needed to reliably trigger this phenomenon. This will then provide the basis for developing a new algal biotechnology optimised for luxury uptake of polyphosphate. While there are still several key questions that need to be answered there is potential for this to lead to a process which could be as significant to pond systems as the development of enhanced biological phosphorus removal was for the activated sludge process.

Waterbird use of different treatment stages in waste-stabilisation pond systems

The significance of waste-stabilisation ponds (WSPs) to waterbirds has been well documented, but WSP differ depending on their place and purpose in the sewage-treatment system, and there is little information on how birds use these different types of pond. In mid-winter (July) 2012, waterbirds were counted on WSP at 18 sewage-treatment plants in the Goulburn Valley, Victoria. Winter-storage and maturation ponds supported greater abundance, density (birds ha−1) and richness of waterbirds than aerated and anaerobic ponds. There were no significance differences in the number of species per hectare among types of pond. The abundance and density of diving waterfowl on maturation and winter-storage ponds was greater than on anaerobic and aerated ponds. A multivariate analysis revealed that waterbird community composition (based on both abundance and density) differed significantly between maturation ponds and anaerobic ponds (P <0.001) and also between winter-storage and anaerobic ponds (P <0.01). Comparing among types of WSPs, the waterbird communities of anaerobic ponds were the most distinct and winter-storage and maturation ponds the least different. Although the primary objective of a treatment plant is to treat sewage there is some design flexibility and, where possible, increasing the size or number of maturation and winter-storage ponds, or both, would generally benefit waterfowl.