Waste Stabilization Pond System Research Articles

Removal mechanisms of nitrogen in waste stabilization ponds

The aim of this research work was to determine the major nitrogen transformation and removal mechanisms in primary and maturation ponds. To accomplished this objective, nitrogen mass balance in waste stabilization pond system was determined using a dynamic mathematical model in order to elucidate the biological nitrogen transformation mechanisms that are effective for removal of nitrogen in this pond system. Results show that nitrogen removal efficiency in a primary facultative pond unit was 13.2%, which was largely due to net loss of organic nitrogen to sediments (9.76%) and denitrification (3.42%). On the other hand, maturation pond removed 15.2% of nitrogen received in the influent with denitrification (13.55%) being the major pathway for nitrogen removal. Ammonia volatilization was not a predominant mechanism for nitrogen removal in both primary facultative and maturation ponds. The major nitrogen transformation routes were mineralization and ammonia uptake in the primary facultative pond, but ammonia uptake by microorganisms was a predominant nitrogen transformation mechanism in maturation pond.

Greenhouse gas emissions from stabilization ponds in subtropical climate

Waste stabilization ponds (WSPs) are a cost-efficient method to treat municipal and non-toxic industrial effluents. Numerous studies have shown that WSPs are a source of greenhouse gas (GHG). However, most reports concerned anaerobic ponds (AP) and few have addressed GHG emissions from facultative (FP) and aerobic/maturation ponds (MPs). In this paper, GHG emissions from three WSP in series are presented. These WSPs were designed as anaerobic, facultative and aerobic/maturation and were treating agricultural wastewater. CH4 fluxes from 0.6±0.4 g CH4 m−2 d−1 in the MP, to 7.0±1.0 g CH4 m−2 d−1 in the (AP), were measured. A linear correlation was found between the loading rates of the ponds and CH4 emissions. Relatively low CO2 fluxes (0.2±0.1 to 1.0±0.8 g CO2 m−2 d−1) were found, which suggest that carbonate/bicarbonate formation is caused by alkaline pH. A mass balance performed showed that 30% of the total chemical oxygen demand removed was converted to CH4. It has been concluded that the WSP system studied emits at least three times more GHG than aerobic activated sludge systems and that the surface loading rate is the most important design parameter for CH4 emissions.

English

  Nitrogen mass balance in waste stabilization pond system at the University of Dar es Salaam was determined using a dynamic mathematical model in order to elucidate the biological nitrogen transformation mechanisms that are effective for removal of nitrogen in this pond system. Results show that the pond system removed 4741 g/day of nitrogen from an influent load of 8036 kg/day, which is equivalent to 59% removal efficiency. The overall dominant nitrogen removal mechanism was denitrification, which was responsible for 77.5% of the removed nitrogen. Other permanent nitrogen removal mechanisms were net loss of nitrogen to sediments and volatilization, which contributed 18.2 and 4.3% of the removed nitrogen, respectively. However, sedimentation was the major nitrogen removal mechanism in primary facultative pond, which was responsible for 73.7% of the total nitrogen removed in that pond. On the other hand, denitrification was the major nitrogen removal mechanism in secondary facultative ponds (F2 and F3) and maturation pond, M, which contributed about 95.0, 89.4 and 89.1% of the total nitrogen removed from these ponds, respectively. The major nitrogen transformation routes were mineralization and ammonia uptake in the primary facultative pond F1. In secondary facultative pond F2, nitrification and denitrification were the dominant nitrogen transformation mechanisms, while in secondary facultative pond F3 and maturation pond M, ammonia uptake was the dominant transformation route. The results obtained in this work may be used as a management tool in assessing the levels of nitrogen compounds in waste stabilization ponds and thus protect the water bodies downstream.     Key words: Nitrogen dynamics, waste stabilization ponds, nitrogen removal, mathematical modeling

Treatment of seasonal wastewater flows in a two-pond system

A waste stabilisation pond system comprising two ponds was used to treat a seasonal discharge from a summer campsite in the UK. Despite a short retention time and relatively high surface loading, the first pond was able to acclimate rapidly to the incoming wastewater, although dissolved oxygen (DO) concentrations remained low. Successful operation was due in part to initial dilution of incoming load at the start of the season by treated water retained over the winter period. The two ponds in series produced a final effluent which met typical chemical and biochemical oxygen demand standards for discharge to inland waters; as expected nutrient concentrations were above typical limit values, making land application for irrigation a preferred option. The system performance was adversely affected by short periods (3–4 days) of low average light intensity, leading to reduced chlorophyll-a and DO concentrations which did not immediately respond to subsequent increases in irradiance. A light-dark bottle technique, adapted to determine net oxygen production potentials under standard conditions of illumination, mixing and temperature, was found to provide an excellent indicator of pond metabolic status and treatment potential.

Performance comparison and economics analysis of waste stabilization ponds and horizontal subsurface flow constructed wetlands treating domestic wastewater: A case study of the Juja sewage treatment works

The performance, effluent quality, land area requirement, investment and operation costs of a full-scale waste stabilization pond (WSP) and a pilot scale horizontal subsurface flow constructed wetland (HSSF-CW) at Jomo Kenyatta University of Agriculture and Technology (JKUAT) were investigated between November 2010 to January 2011. Both systems gave comparable medium to high levels of organic matter and suspended solids removal. However, the WSP showed a better removal for Total Phosphorus (TP) and Ammonium (NH4+–N). Based on the population equivalent calculations, the land area requirement per person equivalent of the WSP system was 3 times the area that would be required for the HSSF-CW to treat the same amount of wastewater. The total annual cost estimates consisting of capital, operation and maintenance (O&M) costs were comparable for both systems. However, the evaluation of the capital cost of either system showed that it is largely influenced by the size of the population served, local cost of land and the construction materials involved. Hence, one can select either system in terms of treatment efficiency. When land is available other factor including the volume of wastewater or the investment, and O&M costs determine the technology selection.

CFD study to determine the optimal configuration of aerators in a full-scale waste stabilization pond

Aerated lagoons (ALs) are important variants of the pond wastewater treatment technology that have not received much attention in the literature. The hydraulic behaviour of ALs and especially the Facultative aerated lagoons (FALs) is very complex since the aeration in these systems is designed for oxygen transfer but not necessarily to create complete mixing. In this work, the energy expenditure of the aerators was studied by means of a scenario analysis. 3D CFD models (one phase and multiphase) of a 3 ha FAL in a waste stabilization pond system in Cuenca (Ecuador) were built for different configurations of aerators. The thrust produced by the aerators was modelled by an external momentum source applied as velocity vectors into the pond fluid. The predictions of a single phase model were in satisfactory agreement with experimental results. Subsequently, a scenario analysis assessing several aeration schemes with different numbers of aerators in operation were tested with respect to velocity profiles and residence time distribution (RTD) curves. This analysis showed that the aeration scheme with all 10 aerators switched on produces a similar hydraulic behaviour compared to using only 6 or 8 aerators. The current operational schemes comprise of switching off some aerators during the peak hours of the day and operating all 10 aerators during night. This current practice could be economically replaced by continuously operating 4 or 6 aerators without significantly affecting the overall mixing. Furthermore, a continuous mixing regime minimises the sediment oxygen demand enhancing the oxygen levels in the pond.

<i>Arthrospira</i> (Spirulina) in tannery wastewaters Part 1: The microbial ecology of tannery waste stabilisation ponds and the management of noxious odour emissions using microalgal capping

We investigated the problem of noxious gas and odour emissions in zero-discharge evaporative tannery waste stabilisation ponds. These have been little-studied systems although they present one of few options for the management of tannery wastewaters in highly water-stressed areas. A three-year study of the microbial ecology of an evaporative waste stabilisation ponding cascade was undertaken and a descriptive account of the biology and the physico-chemical parameters related to odiferous gas release is reported. Large populations of Arthrospira (Spirulina) dominated the latter facultative ponds in the cascade where odour emission was substantially reduced compared to initial anaerobic ponds. Photosynthetic productivity maxima of up to 9 000 mg∙m-2∙day-1 carbon fixation were measured in bloom conditions. Arthrospira production was associated with an oxygenated, alkaline layer established on the surface of facultative ponds (0.35 m in depth) in which oxidation of sulphide and ammonia, and the trapping of other odour-causing compounds was observed. An attempt was made to achieve comparable odour control in the anaerobic ponds by capping with recirculated microalgae-enriched effluent from facultative ponds. While this was shown to be effective in establishing an Arthrospira-dominant surface layer and an associated control of odour emissions in anaerobic ponds, large recirculation volumes (2:1) were required to maintain the Arthrospira population. Elevated salinity of recirculated facultative pond waters also negatively impacted the evaporative function in the low-salinity initial ponds in the cascade. An alternative method of Arthrospira capping was investigated which involved the construction of a free-standing high rate pond alongside the waste stabilisation pond system, and using a controlled feed of raw tannery effluent for optimising the cultivation of Arthrospira biomass. High biomass productivity was achieved in this unit (12.87 g∙m-2∙day-1), using a low feed to effluent loading volume ratio (0.21:1) and subsequent capping of anaerobic ponds from this source achieved odour control comparable to facultative ponds. This study has shown that management of the odour problem in waste stabilisation ponds is possible and that leather production using the zero-discharge evaporative disposal operation may be compatible with a level of both environmental and social acceptability of these systems. Odour problems, alone, should thus not constrain tanning as one of the few industrial agricultural activities available in rural economies.Keywords: tannery, wastewater, waste stabilisation ponds, odour, noxious gas, Spirulina, Arthrospira, microalgal biomass

Use of waste stabilization ponds’ systems in Mediterranean Europe

This paper is a review of the use of waste stabilization ponds (WSPs) systems in Mediterranean Europe. More specifically, it aims at registering the situation and the efficiency of waste stabilization ponds’ systems in Greece, Italy, Spain, Portugal, France, and Cyprus. For that reason, the systems’ efficiency for the removal of suspended solids (SS), BOD5, COD, N-total, N-NH4, P-total, and F. coliforms is estimated. The possibility of effluents’ reuse, according to their quality, is also examined. All the aforementioned countries were selected because they have similar climate and they are all European Union member states: therefore, any differences in waste stabilization ponds’ popularity and efficiency as well as in the legislation regarding the reuse of the ponds’ effluents is also interesting. In Greece, the use of waste stabilization ponds is limited and although most of the existing ponds are not adequately designed, constructed, operated, and maintained, the systems’ efficiency is satisfactory.

Case study on evaluation of the performance of waste stabilization pond system of Jodhpur, Rajasthan, India

The objective of this study is to find out physico-chemical and microbiological characteristics of influent and effluent generated by the sewage treatment plant of Jodhpur city. The treatment plant was constructed in the year 2003–2004 and based on waste stabilization pond (WSP) system. The treatment capacity of the plant is 45 ML/d. Relationship between different physico-chemical and microbiological parameters were studied. After the treatment of wastewater in WSP, average removal of BOD, COD, TSS and TKN were 84.1, 53.4, 79.7 and 61.7% respectively. Average removal of Total Coliforms (TC), Fecal Coliforms (FC), E. coli and Fecal Streptococci (FS) were 2.79 logs, 2.47 logs, 1.65 logs and 1.58 logs respectively. Maximum efficiency of fecal bacteria removal was found during the summers (2.7 to 4.0 log units) and minimum in winters (1 to 1.8 log unit). Further correlation of temperature, pH and biological oxygen demand with TC, FC, E. coli and FS were studied. Among all these parameters temperature shows highest correlation with microbiological parameters as follows: TC (−0.85), FC (−0.62), E. coli (−0.65) and FS (−0.75). High ambient temperature, long photoperiod and high intensity of light can be considered as the major factor for the removal of fecal indicators during the sewage treatment. After treatment pH, BOD, COD, TSS and TKN were found within the permissible limit of Central Pollution Control Board, India. The observed values of fecal indicator organisms are higher than the permissible limit of World Health Organization (WHO). There are no maturation ponds in the treatment plant; construction of maturation ponds will provide better removal of fecal coliforms.

Operation and recovery of a seasonally-loaded UK waste stabilisation pond system

An intermittent discharge waste stabilisation pond system was trialled for treatment of a seasonal wastewater load from a campsite. The system showed rapid acclimatisation to incoming load, with chlorophyll-a exceeding 700 mg l(-1) within 2 weeks and filtered and unfiltered effluent biochemical oxygen demand below 20 and 30 mg l(-1) respectively. Good performance continued for some weeks, after which photosynthetic oxygenation capacity in the first pond was seriously impaired by a shock loading believed to include fatty material. Inflow to the system was suspended and a surface film was broken up, after which the pond recovered within an 8-day period. Laboratory experiments indicated that interventions such as artificial aeration and dilution with effluent had no beneficial effect although mixing may have increased the rate of recovery.

Effect of Hydraulic Retention Time (HRT) on Surveillance of Coliforms in Waste Stabilization Pond (WSP) System in Central India

The content of total coliforms and fecal coliforms were measured for the different ponds (anaerobic, facultative and maturation) in the year 2008-09 for waste stabilization pond (WSP) system in terms of Log 10 reduction value and decay rate (k d -1 ) in order to determine the efficacy of waste stabilization ponds with respect to their hydraulic retention time (HRT). Physical and chemical parameters (temperature, hydrogen ion concentration, total suspended solids and total dissolved solids) were also determined with aim of finding the factors which influence the rate of coliforms removal. The results indicate the surveillance of coliforms were most favored in anaerobic cell and lest favored in maturation cell with decay rate to an average of (k d-1 =2.92); (k d-1=4.88); (k d-1 = 5.83) and (k d-1=2.80) and (k d -1 =4.30); (k d -1 =5.89) for total coliforms and fecal coliforms observed for anaerobic, facultative and maturation cells respectively. The highest removal of coliforms (total and fecal coliforms) between 3.37 log10 to 4.0 log10 was observed for maturation cells with hydraulic retention time (HRT) of 5 days each and two maturation ponds in series.

Long-term performance and operational strategies of a poultry slaughterhouse waste stabilization pond system in a tropical climate

This paper discusses the performance of a poultry slaughterhouse wastewater treatment plant (WWTP) in a tropical country and operating strategies that were applied over 84 months to this WWTP. The WWTP consisted of a dissolved air flotation (DAF) system, anaerobic ponds (APs) and a facultative pond (FP). The organic loading rates applied to the APs ranged from 0.26 to 1.05kgBOD/m3day, and the hydraulic retention time ranged from 2.2 to 3.8days. The resultant COD and BOD removal efficiencies were 42±11% and 38±15%, respectively. The FP surface loading was up to 983kgBOD/haday. The main observed events in the WWTP processes over this period were organic overload, low chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies and color change from green to reddish at the FP. Molecular biology techniques were used to identify microbial groups in the FP in the period of low organic matter removal efficiency and when the liquid became reddish. Sunny conditions favored anoxygenic photosynthesis, the growth of purple nonsulfur bacteria (such as Rhodocyclales-like organisms), and green nonsulfur bacteria (such as Chloroflexi-like organisms). Mechanical aeration at the inlet of the FP restored the water to its original color and increased the COD and BOD removal efficiencies. Based on the BOD removal efficiencies of 89%, after the installation of aerators, the operating strategies illustrate the WWTP system's capacity and versatility to adapt to load variations.

Promoting sustainable sanitation through wastewater-fed aquaculture: a case study from Ghana

Several of the 10 key challenges targeted by the African Water Vision 2025 are directly or indirectly related to human waste management, in particular strengthening the financial base for providing adequate sanitation services. This case study describes a novel approach to improving the operation and maintenance of a waste stabilization pond system in Ghana by turning it into a dual-purpose wastewater treatment plant and commercial fish farm. Results of a collaborative pilot study between private, public and academic partners to test the institutional and technical feasibility of the model as well as the public health impacts are presented.

Macrophyte waste stabilization ponds: An option for municipal wastewater treatment

The objective of this research is to evaluate the performance of macrophyte waste stabilization pond system for municipal wastewater collected from Taxila (Pakistan). A model of macrophyte waste stabilization pond system was operated for six trials with each trials comprising different detention times that is 3, 5, 7 and 10 days, respectively. For the treatment, locally available macrophyte (water hyacinth) was used. To evaluate the performance of macrophyte waste stabilization pond, BOD5, TDS, TSS, COD, faecal coliform and Nitrogen for the effluent from pond model were measured at each detention time of every trial after ensuring steady state conditions. The influent values of same parameters have been measured at the start of each trial as the wastewater sample was collected from the municipal sewer. The average reduction of effluent value of each parameter varies from 30 to 48%, that is BOD5 (48%), TDS (31%), TSS (30%), COD (42%), faecal coliform (45%), and Nitrogen (40%). The mechanisms of pollutant removal in this system include both aerobic and anaerobic microbiological conversions, sorption, sedimentation, volatilization and chemical transformations. There is currently no macrophyte wastewater waste stabilization pond system under study/practice in many of the developing countries; therefore, for the promotion of macrophyte based waste stabilization system detailed pilot scale studies should be conducted for municipal sewage under local environmental conditions to explore the treatment efficiency of the system. Also, it is necessary that macrophyte system be used as treatment facility for wastewater because their performance is comparable to conventional wastewater treatment plants and since the system has very low operation and maintenance costs. Key words: BOD5, Eicchornia crassipes, macrophytes, municipal sewage, water hyacinth, wastewater treatment.

Evaluation of DNA extraction methods for freshwater eukaryotic microalgae

The use of molecular methods to investigate microalgal communities of natural and engineered freshwater resources is in its infancy, with the majority of previous studies carried out by microscopy. Inefficient or differential DNA extraction of microalgal community members can lead to bias in downstream community analysis. Three commercially available DNA extraction kits have been tested on a range of pure culture freshwater algal species with diverse cell walls and mixed algal cultures taken from eutrophic waste stabilization ponds (WSP). DNA yield and quality were evaluated, along with DNA suitability for amplification of 18S rRNA gene fragments by polymerase chain reaction (PCR). QiagenDNeasy® Blood and Tissue kit (QBT), was found to give the highest DNA yields and quality. Denaturant Gradient Gel Electrophoresis (DGGE) was used to assess the diversity of communities from which DNA was extracted. No significant differences were found among kits when assessing diversity. QBT is recommended for use with WSP samples, a conclusion confirmed by further testing on communities from two tropical WSP systems. The fixation of microalgal samples with ethanol prior to DNA extraction was found to reduce yields as well as diversity and is not recommended.

A compartmental model to describe hydraulics in a full-scale waste stabilization pond

The advancement of experimental and computational resources has facilitated the use of computational fluid dynamics (CFD) models as a predictive tool for mixing behaviour in full-scale waste stabilization pond systems. However, in view of combining hydraulic behaviour with a biokinetic process model, the computational load is still too high for practical use. This contribution presents a method that uses a validated CFD model with tracer experiments as a platform for the development of a simpler compartmental model (CM) to describe the hydraulics in a full-scale maturation pond (7 ha) of a waste stabilization ponds complex in Cuenca (Ecuador). 3D CFD models were validated with experimental data from pulse tracer experiments, showing a sufficient agreement. Based on the CFD model results, a number of compartments were selected considering the turbulence characteristics of the flow, the residence time distribution (RTD) curves and the dominant velocity component at different pond locations. The arrangement of compartments based on the introduction of recirculation flow rate between adjacent compartments, which in turn is dependent on the turbulence diffusion coefficient, is illustrated. Simulated RTD’s from a systemic tanks-in-series (TIS) model and the developed CM were compared. The TIS was unable to capture the measured RTD, whereas the CM predicted convincingly the peaks and lags of the tracer experiment using only a minimal fraction of the computational demand of the CFD model. Finally, a biokinetic model was coupled to both approaches demonstrating the impact an insufficient hydraulic model can have on the outcome of a modelling exercise. TIS and CM showed drastic differences in the output loads implying that the CM approach is to be used when modelling the biological performance of the full-scale system.

Phosphate release from waste stabilisation pond sludge: significance and fate of polyphosphate

Net phosphorus removal from waste stabilisation pond (WSP) systems is governed by the rate of phosphorus incorporation into the sludge layer and the rate of phosphorus release from this sludge back to the overlying wastewater. Luxury uptake of phosphorus by microalgae has been shown to occur under WSP conditions in the laboratory; however, the significance of this mechanism and the fate of polyphosphate contained in the settled solids have not previously been investigated. In this work the analysis of sludge samples from three WSP showed that up to 71% of the total phosphorus in the sludge was in the form of polyphosphate. This indicates that polyphosphate accumulation could potentially be an important mechanism for phosphorus sequestration in WSP and challenges the common view that chemical precipitation is the predominant phosphorus removal mechanism in these systems. The release of phosphate from WSP sludge samples was monitored in the laboratory. The samples from two different pond systems had release rates in the order of 4.3 microgP/gTSS.d. However, the third sample which was collected during an algal bloom had a release rate of 12.4 microgP/gTSS.d. Phosphate release from fresh microalgal sludge grown under laboratory conditions was also studied and was shown to have a release rate of 160 microgP/gTSS.d. Analysis of polyphosphate during the experiments on laboratory grown microalgal sludge showed that polyphosphate was indeed degraded resulting in phosphate release. Interestingly, after the initial release phase phosphorus was assimilated by the biomass and some polyphosphate was reformed. It is likely that this is due to bacterial growth in the sludge.

Thermo-tolerant coliform bacteria decay rates in a full scale waste stabilization pond system in Northeast Brazil

This paper presents the results for thermo-tolerant coliform (TTC) decay rates (K(b)) in a full scale WSP system located in Natal-RN, northeast Brazil. The series comprises a primary facultative pond (2 m deep), followed by two maturation ponds (1.5 m deep) giving a total area of 11 ha. The influent sewage and the pond effluents were monitored weekly during a seven month period. The results showed that the K(b) values predicted by the Marais equation assuming a hydraulic regime of complete mixing overestimated TTC die-off rates. The K(b) value adopted in the project design was 6.20 d(-1) but the mean value found for the WSP system during the monitoring programme was only 0.85 d(-1). This value is low compared to the values cited in the literature for shallow ponds (<1.25 m deep) but similar to values for deeper ponds. The sub optimal TTC removal rate in this WSP system may be caused by the adoption of too high a K(b) value at the design stage and the negative influence of high wind conditions on the mixing regime in the water columns of the ponds. Thus values for K(b) adopted at the design stage of WSP systems should be coherent with the hydraulic flow model, the type of pond, pond depth, and with the surface organic loading.

Mechanisms for Parasites Removal in a Waste Stabilisation Pond

A waste stabilisation pond (WSP) system formed by two anaerobic ponds, a facultative pond and a maturation pond was studied from December 2003 to September 2004 in north-western Spain in order to evaluate its efficiency in the removal of faecal indicator bacteria (total coliforms, Escherichia coli, faecal streptococci), coliphages, helminth eggs and protozoan (oo)cysts (Cryptosporidium and Giardia). Furthermore, sediment samples were collected from the bottom of the ponds to assess the settling rates and thus determine the main pathogen removal mechanisms in the WSPs system. The overall removal ranged from 1.4 log units for coliphages in the cold period to 5.0 log units for E. coli in the hot period. Cryptosporidium oocysts were reduced by an average of 96%, Giardia cysts by 98% and helminth eggs by 100%. The anaerobic ponds showed significantly higher surface removal rates (4.6, 5.2 and 3.7 log (oo)cysts/eggs removed m(-2) day(-1), respectively) than facultative and maturation ponds. Sunlight and water physicochemical conditions were the main factors influencing C. parvum oocysts removal both in the anaerobic and maturation ponds, whereas other factors like predation or natural mortality were more important in the facultative pond. Sedimentation, the most commonly proposed mechanism for cyst removal had, therefore, a negligible influence in the studied ponds.

Fate of coliforms and pathogenic parasite in four full-scale sewage treatment systems in India

The occurrence and removal of fecal indicators (total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS)) and pathogens (helminthes eggs) were studied in various municipal wastewater treatment processes (UASB + FPU, ASP, EA, WSP). The reductions in TC and FC concentrations were usually between 2.0 and 2.5 log units in up-flow anaerobic sludge blanket reactor incorporated with final polishing unit (UASB + FPU). Almost similar reduction was observed in activated sludge process system (ASP) and waste stabilization ponds system (WSP), while it was log 3.0 in extended aeration system (EA). UASB + FPU and WSP systems were observed more efficient to reduce helminthes eggs at almost 100%, whereas only 97% removal was observed in case of ASP and EA system. In addition to monitoring of indicator organisms, turbidity, suspended solids (SS), and biochemical oxygen demand (BOD) were used as indirect measure of the potential presence of microorganisms. Interrelationship of BOD, SS, and turbidity with fecal indicator bacteria concentration in influent and effluent manifest that improvement of the microbiological quality of wastewater is strongly linked to the removal of BOD and SS.