Waste Stabilization Pond System Research Articles

Post-treatment of UASB reactor effluent in waste stabilization ponds and in horizontal flow constructed wetlands: a comparative study in pilot scale in Southeast Brazil

The results of a 20-month period study in Brazil were analyzed to compare horizontal-flow constructed wetlands (CW) and waste stabilization pond (WSP) systems in terms of land area requirements and performance to produce effluent qualities for surface water discharge, and for wastewater use in agriculture and/or aquaculture. Nitrogen, E. coli and helminth eggs were more effectively removed in WSP than in CW. It is indicated that CW and WSP require similar land areas to achieve a bacteriological effluent quality suitable for unrestricted irrigation (10(3) E. coli per 100 mL), but CW would require 2.6 times more land area than ponds to achieve quite relaxed ammonia effluent discharge standards (20 mg NH(3) L(-1)), and, by far, more land than WSP to produce an effluent complying with the WHO helminth guideline for agricultural use (< or =1 egg per litre).

Dynamics of industrial waste stabilization pond treatment process

Waste stabilization pond is an artificial ecosystem; its performance is governed by the nature of the biological communities it supports. These are primarily used as secondary effluent treatment plants to polish the effluents. However, they are also used to treat the raw sewage and industrial effluents. In the present study, the functioning of a waste stabilization pond system from an industrial complex located in Goa was taken up. The raw waste released by the industrial complex and the final effluent released from the stabilization ponds were analyzed for pH, dissolved oxygen (DO), biological oxygen demand, phosphate content, chlorophyll content, and algal diversity and density. Also, the activities of the enzymes catalase and phosphatase were measured. The study was carried out for a period of 1 year and the data covering pre-monsoon, monsoon, and post-monsoon seasons are tabulated. The study revealed that DO, chlorophyll content, and algal count were maximum during pre-monsoon when compared to monsoon and post-monsoon. Similarly, maximum enzymatic activity was recorded during pre-monsoon and also maximum removal of biological oxygen demand and phosphate was recorded during this period than in monsoon and post-monsoon.

Enhanced phosphorus removal in a waste stabilization pond system with blast furnace slag filters

In this work a tertiary horizontal-flow blast furnace slag (BFS) filter was tested for phosphorus removal under laboratory and field conditions. Laboratory experiments were conducted in a benchscale BFS filter for phosphorus adsorption capacity at equilibrium conditions using P-spiked water. On-site, the performance of a pilot-scale BFS filter was monitored for phosphorus removal from the final effluent of a pilot-scale WSP system located in Esholt (Bradford, UK), which comprises a primary facultative pond and a secondary aerated rock filter (ARF) in series. Adsorption capacity (q) results showed that BFS has high affinity for inorganic P species and it can remove up to 30 g P/ kg BFS; however, q values are strongly dependent on the initial P concentration. The pilot-scale BFS filter tested on-site performed better for longer (<2 mg P/L) than the laboratory-scale filter, even though despite the latter received the same hydraulic and P loadings (1.8 m 3 /m 3 d and 18 g P/ m 3 d, respectively). Both the laboratory and field results showed that BFS filters are an appropriate low-cost technology to upgrading small wastewater treatment systems for phosphorus removal.

Morphological and molecular characterization of cyanobacteria from a Brazilian facultative wastewater stabilization pond and evaluation of microcystin production

The cyanobacterial population in the Cajati waste stabilization pond system (WSP) from Sao Paulo State, Brazil was assessed by cell isolation and direct microscope counting techniques. Ten strains, belonging to five genera (Synechococcus, Merismopedia, Leptolyngbya, Limnothrix, and Nostoc), were isolated and identified by morphological and molecular analyses. Morphological identification of the isolated strains was congruent with their phylogenetic analyses based on 16S rDNA gene sequences. Six cyanobacterial genera (Synechocystis, Aphanocapsa, Merismopedia, Lyngbya, Phormidium, and Pseudanabaena) were identified by direct microscope inspection. Both techniques were complementary, since, of the six genera identified by direct microscopic inspection, only Merismopedia was isolated, and the four other isolated genera were not detected by direct inspection. Direct microscope counting of preserved cells showed that cyanobacteria were the dominant members (>90%) of the phytoplankton community during both periods evaluated (summer and autumn). ELISA tests specific for hepatotoxic microcystins gave positive results for six strains (Synechococcus CENA108, Merismopedia CENA106, Leptolyngbya CENA103, Leptolyngbya CENA112, Limnothrix CENA109, and Limnothrix CENA110), and for wastewater samples collected from raw influent (3.70 μg microcystins/l) and treated effluent (3.74 μg microcystins/l) in summer. Our findings indicate that toxic cyanobacteria in WSP systems are of concern, since the treated effluent containing cyanotoxins will be discharged into rivers, irrigation channels, estuaries, or reservoirs, and can affect human and animal health.

Norovirus Removal and Particle Association in a Waste Stabilization Pond

The presence of norovirus (NoV) genogroup I (GI) and II (GII) was evaluated using real-time reverse transcription polymerase chain reaction (rRT-PCR) in the influent, two midtreatment locations, and final effluent of a three-pond serial waste stabilization pond system from December 2005 through June 2006. Additionally, influent and effluent samples were filtered through a cascade of three membrane filters with sequentially smaller pores to determine the size range of particles with which GI and GII were associated. NoV GI and GII removal occurs primarily in the third pond. Viruses were found on large settleable particles (retained on a 180 microm filter), on smaller suspended particles (retained on a 0.45 microm filter), on colloidal particles (retained on a positively charged 0.45 microm filter), and in the final filtrate. Both GI and GII in influent samples were found to be dominantly associated with particles smaller than 180 microm, thereby suggesting that particle settling is not the main virus removal mechanism in the waste stabilization pond system. On average, NoV detected in filtered effluent samples were associated with particles between 0.45 and 180 microm in diameter (47 and 67% of detected GI and GII, respectively). The presence of NoV GI and GII in the final filtrate of influent and effluent samples shows that positively charged membrane filters often used for viral concentration methods are not capable of trapping all viruses present in wastewater samples.

Removal of Fecal Indicators and Pathogens in a Waste Stabilization Pond System Treating Municipal Wastewater in India

This study assess the removal of fecal indicators (i.e., total coliforms, fecal coliforms, E. coli, fecal streptococci, and pathogens [Salmonella sp. and helminth eggs]) in a full-scale facultative and maturation pond system with primary screening and manual grit removal facility. The capacity of the plant is 6 ML/d. The results showed that the system was able to remove approximately 2.0 to 3.5 log units of fecal indicators and almost 100% of helminth eggs. Meanwhile, Salmonella was not eliminated significantly, as only 1.26 log units removal was found. Removal efficiency of fecal indicator bacteria was reported maximum during summers (3.4 to 4.0 log units) and minimum (1.9 to 2.0 log units) in winters. Further efforts were made to seek the correlation between key physicochemical wastewater quality parameters (biochemical oxygen demand, turbidity, and suspended solids) and indicator microorganisms (total coliforms, fecal coliforms, and fecal streptococci). Among all these parameters, suspended solids showed the highest correlation coefficient (r2) with total coliforms (0.79), fecal coliforms (0.78), and fecal streptococci (0.75). These correlations manifest that the improvement of microbiological quality of wastewater is strongly linked to the removal of suspended solids.

Effects of fish bioturbation on the vertical distribution of water temperature and dissolved oxygen in a fish culture-integrated waste stabilization pond system in Vietnam

The integration of wastewater stabilization with fish culture in a single-pond system is a double-benefit both due to the reclamation of the wastewater and fish production. In conventional fish ponds, it is known that fish activities (bioturbation) result in ecological benefits as they stir the sediment layer, improving aerobic conditions and, enhancing the oxidation of detritus in this layer. However, the effects of the fish bioturbation in integrated wastewater stabilization fish production systems are little known, especially the enhancement of aerobic conditions in the lower layers of the water column where anaerobic conditions dominate, constraining oxidation of organic matter. The present study was designed to evaluate the effects of three factors (fish bioturbation, season and water depth), as well as their interaction, on the vertical distribution of two factors influencing wastewater treatment efficiency in stabilization ponds—water temperature and dissolved oxygen (DO). In contrast to the pond without fish, there was no significant difference in temperature between the water depth (20, 50 and 80 cm) in the pond with fish in the dry season ( P > 0.05). As indicated by DO monitoring in early morning and on a diel basis, in both dry and rainy seasons the DO saturation percentage of the surface layer of water (20 cm) was not different between the ponds with and without fish. However, with an increase in water depth, the DO saturation percentage of the pond with fish was significantly higher than that of the pond without fish ( P < 0.05). Quiescence of DO variation (invariable linear pattern) in the pond without fish at depths of 50 and 80 cm was recorded. Only fish production and water depth factors had significant effects ( P < 0.001), and the interaction between them was highly significant ( P < 0.01).

Environmental Inactivation of Cryptosporidium parvum Oocysts in Waste Stabilization Ponds

The survival of Cryptosporidium parvum oocysts in a waste stabilization pond system in northwestern Spain and the effects of sunlight and the depth and type of pond on oocyst viability were evaluated using an assay based on the exclusion or inclusion of two fluorogenic vital dyes, 4',6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI). All tested factors had significant effects (P < 0.01) over time on C. parvum oocyst viability. Sunlight exposure was the most influential factor for oocyst inactivation. A 40% reduction was observed after 4 days exposure to sunlight conditions compared with dark conditions. The type of pond also caused a significant reduction in C. parvum oocyst viability (P < 0.01). Inactivation rates reflected that the facultative pond was the most aggressive environment for oocysts placed both at the surface (presence of sunlight) and at the bottom (absence of sunlight) of the pond, followed by the maturation pond and the anaerobic pond. The mean inactivation rates of oocysts in the ponds ranged from 0.0159 to 0.3025 day(-1).

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.

Physical and hydrodynamic characteristics of a dairy shed waste stabilisation pond system

Waste stabilization pond systems are widely used to treat animal wastes under highly variable hydraulic loading regimes. These systems have received limited research attention with regard to their hydrodynamic behaviour and the potential impact of shock hydraulic loading on their performance. In this study a two-stage dairy shed waste stabilisation pond system was topographically surveyed to determine the physical shape and the theoretical hydraulic retention time (HRT) of each pond, as well as the extent of sludge accumulation in the primary pond. The primary pond was then subjected to a series of drogue tracking runs whereby weighted floating survey targets with submerged 'sails' were tracked during their movement through the pond at times of peak flow in order to characterise the hydrodynamic behaviour of the pond. The full capacity volumes of the primary and secondary ponds were calculated to be 1285 m3 and 2391 m3, respectively. Sludge had been accumulating in the primary pond at a rate of 0.73 m3/d over a period of 2.4 years and this has reduced the active treatment volume of the pond to 657 m3. Based on mean outflow, the HRTs of the ponds were 40 d and 137 d, respectively. The drogue runs revealed a vortex-like mixing pattern within the pond with higher velocities around the perimeter of the pond between the inlet and outlet, and lower velocities in the centre of the pond. In-pond velocities seemed relatively high in comparison with those from other drogue studies of larger ponds and the surging inflow caused the formation of a flow 'jet' that potentially contributed to significant short-circuiting. The range of influence of this flow jet, however, was limited to within 15 m of the inlet, suggesting that short-circuiting would be likely to occur only under certain high inflow conditions.

Fate of endocrine disrupters in waste stabilization pond systems

The performance in the removal of estrogenicity from wastewater was studied in three wastewater treatment plants (WWTPs). Different treatment processes were evaluated: stabilization ponds and trickling filter. Sampling was performed from the input to the output of the treatment systems. The total estrogenic activity was determined with MCF-7-derived cell lines which express the endogenous estrogen receptor alpha. The two wastewater stabilization ponds with long retention time had high removal of estrogenicity (90% to 95%). Trickling filters despite being effective at removing organic load were less effective in removing estrogenicity (42%), and post tertiary ponds enhanced estrogenicity removal.

Nitrogen removal in a two-stage, re-circulating waste stabilisation pond system

Waste stabilisation ponds are used widely in Australia and other parts of the world for treating wastewater from domestic and a wide range of industrial sources. It remains a popular form of treatment for wastewater for many small rural towns. The development of a two-stage, re-circulating waste stabilisation pond incorporating algal-bacterial biofilm represents a new approach to increasing the functioning biomass within the water column to improve treatment efficiency. This new approach will be a more viable and economical option for most of the existing waste stabilisation ponds to achieve significant nitrogen removal than converting them to another form of biological nutrient removal processes. A laboratory-scale, two-stage, re-circulating system incorporating "Bio-Tube" plastic modules as attached growth medium has been tested using synthetic wastewater. It has been proven that nitrification-denitrification was the primary mechanism for nitrogen removal in such a system operated under complete mix conditions. During the experimental period, average removal efficiencies of 90-95% of ammonia nitrogen and 65-85% of total nitrogen removal were achieved with influent COD of 600 mg/L and total nitrogen of 70 mg/L.

Dynamic variation of supernatant quality in a dairy shed waste stabilisation pond system

An intensive monitoring program of a standard two-stage dairy shed waste stabilisation pond system was undertaken to determine the incidence and extent of spatial and temporal variation of basic physio-chemical parameters, and to shed light on the longer term dynamic nature of in-pond conditions. The anaerobic-facultative pond system, located in a remote rural area, treats wastewater from the hosing down and hydraulic flushing of the milking parlour and holding yard at the farm dairy shed. A number of multi-parameter water quality field monitoring probes were permanently deployed at various locations within the two ponds to enable continuous measurement of temperature, pH, conductivity and dissolved oxygen. In addition, profiling of the supernatant of both ponds was undertaken at different times of the year to examine vertical variation of the same parameters. Continuous monitoring revealed spatial homogeneity in EC and pH levels in the upper metre of both ponds. Physio-chemical parameters also appear to change uniformly across the ponds in response to external stimuli such as rainfall. Neither pond, however, exhibits homogeneity down the profile of the supernatant. Seasonal stratification is prevalent in the facultative pond suggesting poor vertical mixing, while the anaerobic pond is notably affected by sludge accumulation. A long-term pattern of rising conductivity in both ponds indicated accumulation of dissolved salt species in the system due to recirculation of reclaimed effluent for hydraulic flushing of the dairy shed. In the facultative pond, diurnal fluctuations in dissolved oxygen, oxidation-reduction potential and turbidity during warmer months of the year closely followed temperature swings. The extensive data collected in this study provides a detailed picture of the physio-chemical dynamics of two-stage stabilisation pond systems treating dairy shed wastewater.

Experimental and principal component analysis of waste stabilization ponds

Waste stabilization pond system is a popular waste treatment option because of its high treatment efficiency. In spite of its popularity the underlying theory behind it is inadequately understood. Several hypotheses have tried to explain the causes of bacterial degradation. The present study is aimed at determining through principal component analysis the most important variables affecting bacterial degradation in ponds. Data were collected from literature. In addition, samples were also collected from the waste stabilization ponds at the University of Nigeria, Nsukka and analyzed to determine some of the parameters influencing bacterial degradation. Based on the analysis there was significant correlation between several of the variables. The correlations between some of the parameters were corroborated by experimental values obtained. The most important principal component factors were found to be dispersion, loading and light. The result will not only facilitate effective modeling but will also help direct greater research efforts on the significant variables. Journal of Applied Science, Engineering and Technology Vol. 3(1) 2003: 25-30

Comparison of model approaches for predicting coliform removal in waste stabilization ponds

AbstractThis paper compares the two most frequently used approaches for the prediction of faecal coliforms in the effluent (FCe) of waste stabilization ponds (WSPs): the continuous stirred reactor (CSTR) model and the dispersed flow (DF) model. On the basis of theoretical and practical analysis, it is concluded that, under most conditions usually found in practice, the DF model can be expected to predict unrealistically low FCe. This trend is more pronounced the more the flow conditions in the pond(s) approach plug flow, and the higher the average retention time per pond. Model differences in FCe prediction typically deviate from one another by up to 1–2 log units. This can lead to the design of substantially different pond sizes, with footprint differences between the two models of 30–50% not being exceptional. Consequently, on the basis of usually applied model parameters, for the time being it appears safer to use the CSTR model for FCe prediction in WSP systems.

Economic evaluation of sewage treatment processes in India

This paper evaluates the total annual cost including capital and operation and maintenance (O&M) costs for the up-flow anaerobic sludge blanket (UASB) and waste stabilization pond (WSP) systems operated in India. It also compares UASB and WSP systems with the activated sludge process (ASP) and biological aerated filter (BAF) systems in terms of total annual cost and chemical oxygen demand (COD) removal cost by assuming various annual interest rates and land prices. It was found that the relationship between capital and O&M costs per unit size of a UASB or WSP system and its treatment capacity can be established by a first-order equation. The relation between the cost of organic removal and capital or O&M cost for various sewage treatment systems at various annual interest rates revealed that, for the Indian context, UASB could be the most suitable option in terms of expenses and treatment efficiency.

Nitrogen removal in a small waste stabilization pond containing rock filters

This study analyzes samples taken from 15 separate locations inside a small waste stabilization pond system in New Zealand. The system consisted of six ponds in series with rock filters installed between the final five ponds. The study aimed to determine the relative importance of the ponds and rock filters for nitrogen removal, for a typical effluent quality of 10 g/m3 total nitrogen during the 7 month study period. The results suggest that the most significant nitrogen removal occurred in the ponds rather than the rock filters. Comparison of removal rates to nitrogen accumulation in the sludge and estimates of ammonia volatilization suggest that the most likely mechanism for nitrogen removal is nitrification and denitrification. Possible sites for nitrification are explored in relation to theoretical principles and it is suggested that there may be adequate aerobic surface area on the banks of small-scale ponds to allow significant fixed film nitrogen reduction. A simple model is proposed that predicts nitrogen removal based on a constant removal rate proportional to the aerobic bank surface area. Key words: waste stabilization ponds, nitrogen, rock filters, nitrification, denitrification.

Primary facultative ponds in the UK: the effect of operational parameters on performance and algal populations

Waste stabilisation pond systems in the UK are used to treat effluents from small rural communities where there are large fluctuations in both BOD load and inflow; the facultative ponds in these systems have a wide range of hydraulic retention times: between 11-86 days. Low hydraulic retention times in UK ponds are sometimes accompanied by a high BOD loading, although some have a low BOD loading due to high inflows of dilute wastewater. It is not certain whether the performance is affected by the short hydraulic retention time or high BOD loading. A pilot-scale experiment tested the effect of hydraulic retention time (20-60 days) on primary facultative pond performance whilst keeping the BOD loading constant at 80 kg/ha d. It was found that no significant loss of performance was experienced at the test range for BOD and ammonia removal; some loss in SS removal was noted at 20 days' retention time. The effect of BOD loading on the maintenance of algal populations during winter (November(February) was tested at loadings of 50 and 80 kg/ha d. Although there was a significant difference in the concentrations of chlorophyll a and dissolved oxygen between the two loadings, there was no effect on performance.

Escherichia coli removal in waste stabilization ponds: a comparison of modern and classical designs

Two PC-based waste stabilization pond design procedures, based on parameter uncertainty and 10,000-trial Monte Carlo simulations, were developed for a series of anaerobic, facultative and maturation ponds to produce < or = 1000 E. coli per 100 ml for both 50% and 95% compliance. One procedure was based on the classical Marais equations and the other on the modern von Sperling equations. For the range of parameter variations selected the classical design procedure required less land area and had a shorter hydraulic retention time than the modern design procedure. For both procedures the design for 90% compliance required substantially more land and a longer retention time than the design for 50% compliance. Regulators and designers should seek a balance between system reliability (as set by the percentage compliance specified or adopted) and system costs, especially (but not only) in developing countries. It is recommended that new waste stabilization pond (WSP) systems be designed for compliance with a given E. coli effluent requirement by the classical procedure and that existing overloaded WSP systems be upgraded using the modern procedure.

CFD (computational fluid dynamics) modelling of baffles for optimizing tropical waste stabilization pond systems

CFD modelling of the incorporation of two baffles equally spaced along the longitudinal axis of the pond and with a length equal to 70% of the pond breadth, indicated a potential improvement in the removal of E. coli in a 4-day secondary facultative pond at 25degrees C from 5 x 10(6) per 100 ml in the effluent from a 1-day anaerobic pond to 4 x 10(4) per 100 ml; the reduction in an un-baffled pond was an order of magnitude less effective. The addition of a similarly baffled 4-day primary maturation pond reduced the effluent E. coli count to 340 per 100 ml; the reduction in an un-baffled series was two orders of magnitude less effective. Well designed baffles thus have considerable potential for reducing pond area requirements and hence costs in the hot tropics. These very promising results highlight the need for field studies on baffled pond systems to validate (or allow calibration) of the CFD model used in this study.