Performance Of Waste Stabilization Ponds Research Articles

Effect of Attached Growth on Treatment Performance in Waste Stabilization Ponds

Waste stabilization ponds (WSPs) rely upon natural biochemical reactions for treatment and are used widely across the world. However, WSPs often fail to meet treatment performance expectations due to insufficient hydraulic performance. Installation of baffles can improve hydraulic performance of WSPs by increasing the mean residence time, reducing dead zones, and short circuiting, thus improving pond treatment performance. Theoretically, baffles with the ability to sustain attached growth will increase the possible attachment area of microorganisms and further contribute to nutrient removal. However, to date there have been no full-scale studies exploring attached growth baffles in WSPs. The main objective of this study was to investigate and quantify the effect of attached growth baffles on WSP treatment performance, specifically in terms of improvements in treatment performance provided by attached biofilm compared with hydraulic improvement. A first-order kinetic model was used to predict biological oxygen demand (BOD) removal efficiency, including suspended and biofilm biomass reactions, to determine whether attached growth or hydraulics had the most influence on performance improvement. At the operational WSP scale, we found that although the presence of attached growth on baffles results in a modest (~0.6%) improvement in treatment performance, the most influential factor for improving treatment was improved hydraulics (~5.3%). In model generalization, the change in biofilm thickness and biofilm area had less effect on treatment in WSPs in higher organic loading scenarios; however, a considerable improvement (~12%) in treatment efficiency could be achieved by doubling the total biofilm area. Overall, this study shows that baffles can not only improve WSP hydraulics but can also be used as a medium for increasing biofilm area to improve WSP biological treatment efficiency.

Performance Assessment of Natural Wastewater Treatment Plants by Multivariate Statistical Models: A Case Study

Waste stabilization ponds (WSPs) as natural wastewater treatment plants are commonly utilized for wastewater treatment due to their simple design, low cost, and low-skilled operator requirements. Large-scale studies assessing the performance of WSPs using multivariate statistical models are scarce. Therefore, this study was conducted to assess the performance of 16 full-scale WSPs regarding physicochemical parameters, algae, bacterial indicators, and pathogens (e.g., Cryptosporidium, Entamoeba histolytica) by using multivariate statistical models. The principal component analysis revealed that the chemical pollutants were removed significantly (p < 0.001) through the treatment stages of 16 WSPs, indicating that the treatment stages made a substantial change in the environmental parameters. The non-multidimensional scale analysis revealed that the treatment stages restructured the bacterial indicators significantly (p < 0.001) in the WSPs, implying that the bacterial indicators were removed with the progress of the treatment processes. The algal community exhibited a distinct pattern between the geographical location (i.e., upper WSPs versus lower WSPs) and different treatment stages (p < 0.001). Four out of the sixteen WSPs did not comply with the Egyptian ministerial decree 48/1982 for discharge in agriculture drainage; three of these stations are in lower Egypt (M.K., Al-Adlia, and Ezbet El-Borg), and one is in upper Egypt (Armant). The continuous monitoring of WSPs for compliance with regulatory guidelines with the aid of multivariate statistical models should be routinely performed.

Improving the performance of waste stabilization ponds in an arid climate

Abstract In many parts of the world, waste stabilization ponds (WSPs) are currently the preferred wastewater treatment method for municipal wastewater. The objective of this research is to examine the performance of a WSP in an arid climate region and to identify ways to improve its purification efficiency so that it can meet the criteria for reuse. The results attributed the poor performance to both improper process and physical design after 12 months of physicochemical and bacteriological analyses, as well as monitoring of operation, maintenance and loading rates. In tertiary treatment, maturation ponds are added, an increase in the capacity of the station, and management of the flow rate and retention time for each pond. By simulating the new WSP with GPS-X, the best pond area ratio obtained is 2.5 m2/capita, with a retention time of 4 days for anaerobic ponds, 20 days for facultative ponds and 3 days for two maturation ponds in series, which is suitable and provides reduction rates of BOD and fecal coliforms of 95 and 99%, respectively, with an average effluent concentration of 20 mg/L and 195 CFU. According to the results, well-maintained WSPs provide a viable, self-sufficient and environmentally friendly wastewater treatment solution for irrigation water supply in dry areas.

Hydro-biological characterization and efficiency of natural waste stabilization ponds in a desert climate (city of Assa, Southern Morocco)

Abstract The city of Assa is located in a Saharian area characterized by an arid climate and water scarcity. Like any other Saharian city in a developing country, the city is facing the challenges of rapid urbanization and the need to improve wastewater treatment and management. The main objective of this work is to assess the performance of waste stabilization ponds in an arid area. This evaluation concerns microbiological and physico-chemical monitoring over three and twelve months respectively. Microbiological results indicate bacterial elimination rates of over 90% in autumn–winter due to the effectiveness of facultative ponds with 20–25 days of retention time, water clarity, ponds depth, and high sunlight exposure and penetration. Physico-chemical parameters surpass the Moroccan standards for reuse except Ph and T0 by 20–30%, this wastewater is relatively loaded with various pollutants, especially high organic load and low oxygen content. Statistical analysis has been made by principal component analysis (PCA), and confirms that dissolved oxygen, total suspended solids, COD and BOD5 do not reach the threshold for discharge into the natural environment, and moreover their reuse. For the improvement of the quality of these waters, it is legitimate to provide an upgrade of this plant by a tertiary treatment with maturation ponds.

Performance evaluation of waste stabilization ponds on removal of Listeria spp.: a case study of Isfahan, Iran.

The aim of the present study was to assess performance of waste stabilization ponds (WSPs) on the removal of Listeria spp. in Isfahan, Iran. A total of 104 samples were taken from eight sampling locations from influent and effluent of a wastewater treatment plant (WWTP). Sewage samples were analyzed for the presence of Listeria spp. using selective enrichment protocol. Listeria isolates were also identified by biochemical and polymerase chain reaction (PCR) amplification. Listeria spp. was enumerated by a three tube most probable number (MPN) for total coliform counts (TC), fecal coliform counts (FC), total suspended solids (TSS), and total dissolved solids (TDS). In total, 54/104 (51.92%), 49/104 (47.11%), 36/104 (34.61%), and 27/104 (25.95%) samples were positive for Listeria spp., L. monocytogenes, L. innocua, and L. seeligeri, respectively. The mean MPN/100 mL enumeration of L. monocytogenes for influent, anaerobic, facultative ponds 1, 2, 3, 4 and maturation ponds 1 and 2 were 21.54, 10.61, 8, 5.77, 4, 2.54, 1.38, and 0.46, respectively. The removal percentage of Listeria spp. in the anaerobic, facultative, and maturation ponds were 44.71, 76.5, and 81.4%, respectively. Results showed that the WSPs were able to decrease the Listeria spp. levels significantly, although unable to remove them completely.

Optimization of waste stabilization pond performance for piggery waste treatment using response surface methodology

The treatment of piggery wastewater using the waste stabilisation pond was studied in a semi- continuous process. Optimization of Chemical Oxygen Demand (COD) removal was conducted using response surface methodology where pH, temperature and retention time were independent variables. The Box-Behnken design approach, an experimental design was used for creating set of experimental runs needed for optimizing COD removal. An attempt was also made to optimize COD removal by reducing hydraulic retention time while maintaining pH and temperature of a defined range. Analysis of variance (ANOVA) was conducted on model terms and the results revealed that the coefficient of determination value (R2) of % COD removal was 0.86, 0.88, and 0.86 for the anaerobic, facultative and maturation pond respectively. Highest desirability was obtained for optimum COD % removal and this was 0.89, 0.89 and 1.0 for ponds.The waste stabilisation pond treatment process can effectively be improved on for piggery wastewater treatment.DOI: http://dx.doi.org/10.5755/j01.erem.73.2.17696

Prediction of the waste stabilization pond performance using linear multiple regression and multi-layer perceptron neural network: a case study of Birjand, Iran

Prediction of the waste stabilization pond performance using linear multiple regression and multi-layer perceptron neural network: a case study of Birjand, Iran

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.

Characterizing phosphorus removal in passive waste stabilization ponds in Arctic communities

A majority of communities in the Canadian territory of Nunavut rely on passive waste stabilization ponds (WSPs) for domestic wastewater treatment. Little research has been conducted on the treatment performance of these systems. Therefore, in response to impending federal wastewater regulations, a research program was conducted in order to characterize contaminant removal, with phosphorus a contaminant of particular concern. The performance of WSPs in the Arctic communities of Kugaaruk, Pond Inlet, Grise Fiord, and Clyde River was evaluated from 2011 to 2014. Removal of total phosphorus was highly variable, ranging from 24% (Pond Inlet, 2014) to 76% (Grise Fiord, 2011). The average removal efficiency was 44%. Effluent total phosphorus concentrations generally exceeded 7 mg P/L, partly due to elevated raw wastewater concentrations. Over the course of the treatment season (defined as June to September, when the WSP is thawed), limited additional total phosphorus removal was observed. A fractionation analysis of WSP sediments showed that organic phosphorus and phosphorus bound to aluminum and iron were the predominant forms, which provided insight into primary treatment mechanisms. Further studies on these mechanisms are needed in order to optimize Arctic WSP treatment.

Performance, Compliance and Reliability of Waste Stabilization Pond: Effluent Discharge Quality and Environmental Protection Agency Standards in Ghana

Measuring performance has been arguerably, one of the metric with many facets with different school of thoughts, as there exist different approaches of measuring it. Several of the existing approaches measure such metric by comparison with standards esherined in policy documents and as a result, takes less look to its compliance and reliability of values being matched to an established standards. This study seeks to integrate reliability and compliance into measuring of performance of Waste Stabilization Pond (WSP) and Treatment Plant (TP) as well as to generate the appropriate standard chart tables using the Ghana Environmental Protection Agency (EPA) approved discharge values for physico-chemical and some biological parameters to account for these shortfalls on over reliance of EPA discharge standards. Probability distribution density function was applied on the lognormal distribution function to establish the relationship between the statistical coefficient of variation and the coefficient of reliability based on rth moment about the origin in the moment of generation function to generate the functions of the mean and standard deviation, properties of the standard Z normal distribution were used to establish the coefficient of reliability relationship depending on the coefficient of variation influenced by the standard of deviation. Discharge values of Physico-chemical Parameters measured from the WSP were found be performing acceptably based on the EPA standards, whereas only four of the TP were acceptable. Discharge Values of physico-chemical and biological parameters which are found to be accepted under comparison with EPA standards were found to have compliance levels below what is generally accepted for Waste Stabilization Ponds (WSP) designed compliance. Based on these shortcomings, reference charts were develop to serve as reference points in assessing the various characteristics of compliance and performance of WSPs in Ghana on (28) physico-chemical and biological parameters. These charts are intended to make it easier to assess the performance of WSPs and its corresponding reliability and compliance level to compensate for overreliance on EPA standards alone.

Calibration of a simple model for waste stabilisation pond performance in seasonal climates

The paper describes the calibration of a model for waste stabilisation pond (WSP) performance in seasonal climates, based on the use of readily available climate data sets. Calibration data were taken from a wide geographical area of Canada and the USA, including coastal and moderately seasonal sites. Good agreement with measured values was shown using a biochemical oxygen demand (BOD) decay constant of 0.3 day(-1) for facultative ponds and 0.07-0.1 day(-1) for storage/maturation ponds with a temperature-related Arrhenius constant of 1.05, and a fixed BOD decay constant of 0.007 day(-1) at water temperatures below 0 °C. The results suggested that such models could potentially be used as the basis for WSP design guidelines tailored to a wide range of climatic conditions.

The Effect of Hydraulic Jump on the Performance of Waste Stabilization Ponds

One of the simplest forms of biological treatment processes used in the tropics is the waste stabilization pond (WSP). The relative simplicity and low operating cost of the WSP make it the preferred technology for handling, treatment and disposal of municipal waste for small communities. However, its use in urban areas is limited because of its large area requirement. Hence, the research is aimed at investigating if the introduction of hydraulic jump in the Waste Stabilization Pond can increase treatment efficiency and consequently reduce the land area requirement. Thus, WSPs with varying number of hydraulic jumps were constructed using metallic tanks. The hydraulic jumps were created to introduce turbulence thereby adding dissolved oxygen in the pond. Wastewater samples collected from different points (including inlets and outlets) in the ponds were examined for physio-chemical and biological characteristics for a period of ten weeks. The parameters examined were dissolved oxygen, coliform, biochemical oxygen demand (BOD5), chemical oxygen demand and tracer studies. The efficiencies of the WSPs with respect to these parameters fluctuated with variations in the atmospheric conditions and varying discharge with the highest efficiency obtained from the pond with two hydraulic jumps. The research revealed that the cost of wastewater treatment using hydraulic jump enabled WSP was approximately one and a half times lower than the conventional WSP for the same efficiencies.

Waste stabilization pond performance in Pakistan and its implications for wastewater use in agriculture

Faisalabad is one of the few cities in Pakistan that has a waste stabilization pond (WSP) system. Local farmers complained about the high salinity and low nutrient value of the final effluent from the WSP and preferred the use of untreated wastewater. A one-year study showed a strong increase in salinity from untreated wastewater to final effluent with a clear decline in nitrogen concentration, thereby confirming farmer perceptions. The performance of the WSP was poor and did not comply with World Health Organization (WHO) and Food and Agricultural Organization (FAO) guidelines for irrigation water. The poor performance of the WSP could be attributed to a combination of factors: poor design, the extreme climatic conditions and the large quantities of untreated wastewater which were used in agriculture. In countries such as Pakistan where the use of untreated wastewater has a long history, farmer perceptions should play a pivotal role in the selection of suitable wastewater treatment systems.

Implications for physical design: the effect of depth on the performance of waste stabilization ponds

Studies on experimental primary facultative ponds showed that varying the depth from 1.25 m to 2.3 m had no effect on the rates of BOD removal. In contrast k values for FC removal rates were higher in the shallower (1.25 m) facultative ponds. The risk of odour release via H2S production was higher in the 2.2 m ponds than the 1.25 m ponds and NH3 removal was much better in the 1.25 m facultative ponds. A comparison of the efficiency of shallow 5-pond series (1.0 m and 0.61 m deep) with a 2.2 m deep series showed that the shallow systems were more efficient at FC removal, but the deeper series actually saved land area for the same FC final effluent quality under tropical conditions. However, efficient nutrient removal (N and P) only occurred in the shallow series and effluent standards for nutrient concentrations are unlikely to be met by 2.2 m deep 5-pond series in contrast to the norms for pathogen removal.

Changes in waste stabilisation pond performance resulting from the retrofit of activated sludge treatment upstream: part II – management and operating issues

Bolivar Wastewater Treatment Plant (WWTP) was originally commissioned with trickling filter secondary treatment, followed by waste stabilisation pond (WSP) treatment and marine discharge. In 1999, a dissolved air flotation/filtration (DAFF) plant was commissioned to treat a portion of the WSP effluent for horticultural reuse. In 2001, the trickling filters were replaced with activated sludge treatment. A shift in WSP ecology became evident soon after this time, characterised by a statistically significant reduction in algal counts in the pond effluent, and increased variability in algal counts and occasional population crashes in the ponds. While the photosynthetic capacity of the WSPs has been reduced, the concomitant reduction in organic loading has meant that the WSPs have not become overloaded. As a result of the improvement in water quality leaving the ponds, significant cost savings and improved product water quality have been realised in the subsequent DAFF treatment stage. A number of operating issues have arisen from the change, however, including the re-emergence of a midge fly nuisance at the site. Control of midge flies using chemical spraying has negated the cost savings realised in the DAFF treatment stage. While biomanipulation of the WSP may provide a less aggressive method of midge control, this case demonstrates the difficulty of predicting in advance all ramifications of a retrospective process change.

Changes in waste stabilisation pond performance resulting from the retrofit of activated sludge treatment upstream: part I – water quality issues

This paper describes changes in effluent quality occurring before and after an upgrade to the Bolivar Wastewater Treatment Plant in South Australia. Trickling filters (TF) were replaced with an activated sludge (AS) plant, prior to tertiary treatment using waste stabilisation ponds (WSPs). The water quality in the WSPs following the upgrade was significantly improved. Reductions in total and soluble BOD, COD, TKN, suspended solids and organic nitrogen were recorded and the predominant form of inorganic nitrogen changed from NH(4)-N to NO(2)/NO(3)-N. The reduction in ammonium and potentially toxic free ammonia removed a control upon the growth of zooplankton, which may have contributed to decreases in algal biomass in the final ponds and consequently lower dissolved oxygen. Additionally, changes in inorganic nitrogen speciation contributed to a slightly elevated pH which reduced numbers of faecal coliforms in WSPs. The AS pretreated influent recorded significantly lower inorganic molar N:P ratio (10-4:1) compared to those fed with TF effluent (17-13:1). Algae within the WSPs may now be nitrogen limited, a condition which may favour the growth of nitrogen-fixing cyanobacteria. The decrease in algal biomass and in dissolved oxygen levels may enhance sedimentary denitrification, further driving the system towards nitrogen limitation.

The potential for water hyacinth to improve the quality of Bogota River water in the Muña Reservoir: comparison with the performance of waste stabilization ponds

The potential application of Water Hyacinth (Eichhornia crassipes) in organic matter degradation, sedimentation, nutrient and heavy metal absorption and sulfur reduction in the Muña Reservoir has been tested in experimental lagoons. The lagoons were operated at hydraulic retention times (HRT) of 6, 9 and 15 days. One lagoon was covered with Water Hyacinth, which is naturally growing in the Muña Reservoir, while another lagoon was operated as a conventional oxidation pond. The Water Hyacinth lagoon had better removal efficiencies for almost all parameters measured: BOD5, total suspended solids, COD, nitrogen, phosphorus and heavy metals. The oxidation lagoon was facultative for HRT of 9 and 15 days, and anoxic when operated at 6 days HRT. At HRT of 15 days the water quality in the effluent of the covered lagoon corresponded to 12 mg/l of BOD, 6 mg/l of suspended solids and 0.8 mg/l of hydrogen sulfide. Hydrogen sulfide levels in the Muña reservoir can be substantially reduced at HRT higher than 15 days in both lagoons. The uncovered lagoon had better hydrogen sulfide removal during the day but presents high levels at night. If the hydraulic retention time in the Muña reservoir is increased, the water quality of the Bogota river can be substantially improved for all the HRTs tested in the pilot units. HRT seems to give a better prediction of overall effluent water quality than surface loading. More research is needed in order to define the optimum water hyacinth density in the Muña reservoir to determine its influence on the water quality of the effluent. The influence is expected to be negative due to an internal increase of BOD, solids, nutrients and metals loads due to plant decay.

Effect of tapering on the performance of waste stabilization ponds

A model for wastewater degradation in a tapered waste stabilization pond was derived as a modified Bessel function by materials balance approach. Based on hypothetical data, the tapered model gave lower faecal bacteria removal than the conventional (rectangular) model for various values of dispersion number, die-off rate coefficient, average width and shape factors. The above results were corroborated by data collected from two laboratory ponds operated in parallel; one having a tapered and the other a rectangular surface area. The latter gave slightly higher hydraulic efficiency and BOD 5 removal. Besides, faecal bacteria removal was significantly lower in the tapered pond than in the rectangular pond at 0.10 level of significance. Calculated faecal bacteria reduction using the tapered model was in good agreement with measured data with coefficient of correlation and standard error of 0.904 and 0.014, respectively. Effects of tapering on ponds with respect to construction cost, operational and maintenance ease and accuracy of estimated design parameters are also discussed.

Waste stabilization ponds in France: a report on fifteen years experience

In 1992, a survey was conducted on the performance of waste stabilization ponds in France. The data selected come from a sample of 178 ponds, with an average capacity of 600 p.e., throughout France. For each plant, one or several input--output load measurements over a 24-h period are available. The average organic load level received is approximately 25 kg BOD/ha.d, representing 50% of the nominal load. The quality of the treated water is presented based on the type of sewerage system feeding the ponds. The results appear dispersed, however; in 70% of the cases the concentrations in COD and BOD on filtered samples are under 120 mg/l and 40 mg/l, respectively, and the concentration in TSS under 120 mg/l (discharge standards in France for waste stabilization ponds). The reductions in nitrogen and phosphorus nutrients are on average from 60% to 70%. The influence of different parameters (sewerage system type, organic load, season, age of plant, etc.) was studied. The results appear noticeably worse when the ponds receive wastewater from a strictly separate sewerage system.

Purple non-sulfur bacteria and their influence on waste stabilisation pond performance in the Yemen Republic

In the semi-arid Yemen Republic wastewater treatment has high priority to control the spreading of communicable diseases and to make the effluent fit for reuse in agriculture. Experience with existing waste stabilisation ponds has in many cases been unfavourable because of poor BOD removal and odour problems. The raw domestic sewage at the Sana'a waste stabilisation ponds is very strong in terms of BOD, COD, TSS and sulfate, and its ammonia levels are excessively high (150-200 mg N-[NH3 + NH4+]L). The combination of high temperature, high organic loading rates and the presence of sulfides, due to conversion of sulfate in the anaerobic ponds, appears to favour development of anoxygenic photo-heterotrophic purple non-sulfur bacteria Rhodopseudomonas spp. in facultative ponds. Some species can oxidise sulfides to sulfate using light; they lend the water its typical reddish-pink colour and cause high turbidity which may disfavour algal growth. Also, in large tracts of the ponds the high ammonia levels suppress algal growth, as demonstrated in lab experiments. Consequently, low DO and poor C-metabolisation prevail in the ponds. Low DO in turn again creates conditions stimulating microbial sulfate reduction. Field data from other facultative ponds in Yemen suggests that a minimum retention time in the facultative ponds of 20-25 days is necessary to provide ecological conditions allowing algae to outcompete purple bacteria.