Facultative Stabilization Ponds Research Articles

MATHEMATICAL MODELING REGIME STEADY STATE FOR DOMESTIC WASTEWATER TREATMENT FACULTATIVE STABILIZATION PONDS

This paper presents a model for natural systems used in Wastewater Treatment Plant (WWTP) Sewon Bantul. The model is modeling development, derived from the physical and biochemical phenomena involved in the biological treatment process. The numerical solution of the resulting on 13 simultaneous systems of nonlinear equations by the Quasi_Newton. Data validation is measured by facultative pond at the inlet and outlet of the pond to the concentration of bacteria, algae, zooplankton, organic matter, detritus, organic nitrogen, NH3, organic phosphor, dissolved phosphorus, Dissolved Oxygen (DO), total coliform, faecal coliform and Biochemical Oxygen Demand (BOD). A simulation model is presented to predict ke performance regime steady state of domestic wastewater treatment facultative stabilization pond. The high degree of significant of at least 10% indicates that the effluent parameters can be reasonably accurately predicted.

Benthic nutrient fluxes and sediment oxygen consumption in a full-scale facultative pond in Patagonia, Argentina

The study of benthic metabolism is an interesting tool to understand the process that occurs in bottom water at wastewater stabilization ponds. Here, rates of benthic oxygen consumption and nutrient exchange across the water-sludge interface were measured in situ using a benthic chamber. The research was carried out during autumn, winter, and summer at a municipal facultative stabilization pond working in a temperate region (Puerto Madryn city, Argentina). Both a site near the raw wastewater inlet (Inlet station) and a site near the outlet (Outlet station) were sampled. Important seasonal and spatial patterns were identified as being related to benthic fluxes. Ammonium release ranged from undetectable (autumn/summer - Inlet station) to +30.7 kg-NH4(+) ha(-1) d(-1) (autumn - Outlet station), denitrification ranged from undetectable (winter - in both sites) to -4.0 kg-NO3(-) ha(-1) d(-1) (autumn - Outlet station), and oxygen consumption ranged from 0.07 kg-O2ha(-1) d(-1) (autumn/summer - Outlet station) to 0.84 kg-O2ha(-1) d(-1) (autumn - Inlet station). During the warmer months, the mineralization of organic matter from the bottom pond acts as a source of nutrients, which seem to support the important development of phytoplankton and nitrification activity recorded in the surface water. Bottom processes could be related to the advanced degree and efficiency of the treatment, the temperature, and probably the strong and frequent wind present in the region.

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.

Nitrification in bulk water and biofilms of algae wastewater stabilization ponds

Nitrogen removal in wastewater stabilization ponds is poorly understood and effluent monitoring data show a wide range of differences in ammonium. For effluent discharge into the environment, low levels of nitrogen are recommended. Nitrification is limiting in facultative wastewater stabilization ponds. The reason why nitrification is considered to be limiting is attributed to low growth rate and wash out of the nitrifiers. Therefore to maintain a population, attached growth is required. The aim of this research is to study the relative contribution of bulk water and biofilms with respect to nitrification. The hypothesis is that nitrification can be enhanced in stabilization ponds by increasing the surface area for nitrifier attachment. In order to achieve this, transparent pond reactors representing water columns in algae WSP have been used. To discriminate between bulk and biofilm activity, 5-day batch activity tests were carried out with bulk water and biofilm sampled. The observed value for Rnitrbulk was 2.7 x 10(-1) mg-N L(-1) d(-1) and for Rbiofilm was 1,495 mg-N m(-2) d(-1). During the 5 days of experiment with the biofilm, ammonia reduction was rapid on the first day. Therefore, a short-term biofilm activity test was performed to confirm this rapid decrease. Results revealed a nitrification rate, Rbiofilm, of 2,125 mg-N m(-2) d(-1) for the first 5 hours of the test, which is higher than the 1,495 mg-N m(-2) d(-1), observed on the first day of the 7-day biofilm activity test. Rbiofilm and Rnitrbulk values obtained in the batch activity tests were used as parameters in a mass balance model equation. The model was calibrated by adjusting the fraction of the pond volume and biofilm area that is active (i.e. aerobic). When assuming a depth of 0.08 m active upper layer, the model could describe well the measured effluent values for the pond reactors. The calibrated model was validated by predicting effluent Kjeldahl nitrogen of algae ponds in Palestine and Colombia. The model equation predicted well the effluent concentrations of ponds in Palestine.

Kinetic hindrance of Fe(II) oxidation at alkaline pH and in the presence of nitrate and oxygen in a facultative wastewater stabilization pond

To better understand the dynamics of Fe2 + oxidation in facultative wastewater stabilization ponds, water samples from a three-pond system were taken throughout the period of transition from anoxic conditions with high aqueous Fe2 + levels in the early spring to fully aerobic conditions in late spring. Fe2 + levels showed a highly significant correlation with pH but were not correlated with dissolved oxygen (DO). Water column Fe2 + levels were modeled using the kinetic rate law for Fe2 + oxidation of Sung and Morgan.[ 5 ] The fitted kinetic coefficients were 5 ± 3 × 106 M− 2 atm− 1 min− 1; more than six orders of magnitude lower than typically reported. Comparison of four potential Fe redox couples demonstrated that the pε was at least 3–4 orders of magnitude higher than would be expected based on internal equilibrium. Surprisingly, measured nitrate and DO (when present) were typically consistent with both nitrate (from denitrification) and DO levels (from aerobic respiration) predicted from equilibrium. Although the hydrous Fe oxide/FeCO3 couple was closest to equilibrium and most consistent with the observed pH dependence (in contrast to predicted lepidocrocite), Fe2 + oxidation is kinetically hindered, resulting in up to 107-fold higher levels than expected based on both kinetic and equilibrium analyses.

Metal availability and uptake by sorghum plants grown in soils amended with sludge from different treatments

Several factors depending on the sludge, the soil, or the combination of both substrates, may affect element availability to plants. In this study, an assessment was done of the effect of two sludges obtained by different processes (activated sludge and facultative stabilization pond) on heavy-metal availability and uptake by sorghum plants in soils with high and low copper contents. Results obtained for DTPA-extractable metal indicated higher metal availability in sludge-amended soils. In addition, sludges caused changes in copper and zinc distribution in soil, indicating in most cases a discrete increase in the more labile metal forms. However, observed changes did not increase heavy metal concentration in plant leaves, indicating that assessment of metal availability by a chemical procedure (single extraction or metal fractionation) would not permit a good prediction of metal bioavailability. On the other hand, sludge application at a rate of 100 t ha −1 to high-copper agricultural soils would not imply greater mobility of this metal on account of a greater sorbing capacity provided by the sludges. Such results would indicate that sludges from wastewater treatment plants, meeting the standards of heavy metal contents, regardless of the process by which they were obtained, may be applied to several kinds of soil, even to high-copper soils, with no risk of increasing heavy metal bioavailability to phytotoxic levels in the short range.

A dynamic mathematical model for wastewater stabilization ponds

A dynamic mathematical model was developed to predict the effluent quality of facultative wastewater stabilization ponds. For a sound representation of sediment–water column, water column–atmosphere interactions and stratification due to variations in dissolved oxygen concentrations, a two-dimensional hydraulic model was employed considering dispersed flow and diffusion in horizontal and vertical directions, respectively. Resulting partial differential equation system was solved using finite difference methods and matrix manipulation techniques. The model has been calibrated and evaluated on the basis of collected data from a full-scale facultative stabilization pond in Selçuk, Izmir. Variations of COD, NH 4-N, PO 4-P, dissolved oxygen, bacteria and algae concentrations with time and the dimensions of the pond were estimated by using the dynamic model. The model can be used for design of new stabilization ponds and also, for improving the effluent quality of existing ponds.

Determination of the inactivation rate of Ascaris eggs in wastewater stabilization pond sludge using dialysis chambers and sludge cores.

The inactivation rate of Ascaris eggs was studied in the sludge layer of a primary, facultative wastewater stabilization pond located in Mexico City. Two independent methods, sludge cores and dialysis chambers, were used, to determine the inactivation rates through which a comprehensive picture of the inactivation was gained. The dialysis chambers provided a detailed picture of the initial inactivation (14 months) at one location in the pond, whereas the sludge cores provided less precise information about the inactivation rate at several locations and over the entire lifetime of the pond (10 years). The inactivation curve was characterized by an initial lag phase, a period of roughly first-order inactivation, and a tailing region. During the first year, 50 to 60% of the eggs were inactivated, after which the rate decreased. Although the observed, initial first-order rate constant was greater than 0.002 d(-1), the average, long-term rate constant was closer to 0.001 d(-1).

Sludge accumulation, properties and degradation in a waste stabilization pond in Mexico

The sludge layer in a primary, facultative wastewater stabilization pond in Texcoco, Mexico was studied. Five sludge cores were taken in the pond, near the entrance, middle, exit, and at the midpoint about 5 m from each side. Each core was stratified into four subsamples and analyzed. Temperature, pH, ORP, and %VS decreased with depth (age) in the sludge layer, whereas ammonia and TS concentrations increased. The concentrations of fecal coliforms and viable helminth eggs also decreased with depth in the sludge layer, but significant concentrations of both organisms were still present in the oldest sludge, which is estimated to be over seven years old (average). From a sludge depth survey it was found that the majority of the sludge accumulated near the inlet of the pond. The average net sludge accumulation rate was estimated to be 24 mm/yr.

Pathogen removal mechanisms in anoxic wastewater stabilization ponds

Anoxic wastewater stabilization ponds can reduce land requirements by as much as two-thirds of that required for facultative ponds and can avoid the environmental nuisances of odour and corrosion, compared with anaerobic ponds. When effluent reuse is to be considered, the aim of wastewater treatment is not only to reduce degradable organic matter but also to remove pathogenic microorganisms. There are many pathogenic agents in domestic sewage and determination of all of them is not practically feasible, so faecal coliform organisms are normally estimated as indicators of health risk. It has been found that the volumetric organic loading on ponds affects pathogen removal inversely and temperature has a positive effect. This was confirmed in the present studies on “anoxic” ponds and, in addition, other environmental factors (light, pH, DO and ORP) were found to have influenced pathogen removal in these ponds, which were loaded in the range between conventional loadings for anaerobic and facultative stabilization ponds. However, pathogen removal in anoxic ponds was not found to be significantly better or worse than in anaerobic or primary facultative ponds and, therefore, maturation ponds would be required following anoxic ponds to achieve an effluent quality suitable for unrestricted irrigation.

Performance evaluation of anoxic and facultative wastewater stabilization ponds

The performance of anoxic and facultative ponds in Jordan was investigated for 12 months. Calculated values of the first order kinetic equation rate for CBOD removal (KCBOD) has resulted in different KCBOD's for different ponds in the same month, at the same temperature. It is evident that factors other than temperature must influence values of KCBOD. The KCBOD values determined were generally lower than those reported in the literature. The maximum value found was only 0.16 (/day). A pond was emptied after 18 months of operation and sediment was found randomly distributed over the pond area, with a depth ranging from 2 to 6 cm (averaging ≈ 4 cm). A simple model has been established to estimate sediment depth (Hs in cm) in terms of the operating time in months (t).

Improving the effluent quality of facultative stabilization ponds by means of submerged aerated biofilters

This paper describes the use of a submerged aerated biofilter (BF) in the tertiary treatment of effluent from facultative stabilization ponds (FSP). The results, obtained over four months of tests, confirm the ability of the BF to remove algae and, principally, to achieve tertiary nitrification. For hydraulic loading rates of 2m3/m2.h, the mean efficiency of the process in the removal of algae (SS) and COD was 58% and 63% respectively. Concentrations above 70 mg SS/1 and 195 mg O2/1 (COD) in the effluent from the ponds was reduced to 30 mg SS/1 and 70 mg O2/1 (COD) in the effluent from the BF. In addition to the removal of organic forms of nitrogen and phosphorus, the biofilter also reaches the soluble COD and ammonia. Tertiary nitrification was achieved with a mean efficiency of 86% for volumetric loads of up to 0.7 kg N-NH4+/m3.day (27°C). For concentrations above 20 mg n-NH4+/1 in the feed, the process can produce with safety effluents with less than 1 mg N-NH4+/1. The period of operation between the 2 successive washings of the bed filter was in the order of three days.

Improving the effluent quality of facultative stabilization ponds by means of submerged aerated biofilters

This paper describes the use of a submerged aerated biofilter (BF) in the tertiary treatment of effluent from facultative stabilization ponds (FSP). The results, obtained over four months of tests, confirm the ability of the BF to remove algae and, principally, to achieve tertiary nitrification. For hydraulic loading rates of 2m3/m2.h, the mean efficiency of the process in the removal of algae (SS) and COD was 58% and 63% respectively. Concentrations above 70 mg SS/1 and 195 mg O2/1 (COD) in the effluent from the ponds was reduced to 30 mg SS/1 and 70 mg O2/1 (COD) in the effluent from the BF. In addition to the removal of organic forms of nitrogen and phosphorus, the biofilter also reaches the soluble COD and ammonia. Tertiary nitrification was achieved with a mean efficiency of 86% for volumetric loads of up to 0.7 kg N-NH4+/m3.day (27°C). For concentrations above 20 mg n-NH4+/I in the feed, the process can produce with safety effluents with less than 1 mg N-NH4+/I. The period of operation between the 2 successive washings of the bed filter was in the order of three days.

Pathogen removal mechanisms in anoxic wastewater stabilization ponds

Anoxic wastewater stabilization ponds can reduce land requirements by as much as two-thirds of that required for facultative ponds and can avoid the environmental nuisances of odour and corrosion, compared with anaerobic ponds. When effluent reuse is to be considered, the aim of wastewater treatment is not only to reduce degradable organic matter but also to remove pathogenic microorganisms. There are many pathogenic agents in domestic sewage and determination of all of them is not practically feasible, so faecal coliform organisms are normally estimated as indicators of health risk.It has been found that the volumetric organic loading on ponds affects pathogen removal inversely and temperature has a positive effect. This was confirmed in the present studies on "anoxic" ponds and, in addition, other environmental factors(light, pH, DO and ORP) were found to have influenced pathogen removal in these ponds, which were loaded in the range between conventional loadings for anaerobic and facultative stabilization ponds. However, pathogen removal in anoxic ponds was not found to be significantly better or worse than in anaerobic or primary facultative ponds and, therefore, maturation ponds would be required following anoxic ponds to achieve an effluent quality suitable for unrestricted irrigation.

Performance evaluation of anoxic and facultative wastewater stabilization ponds

The performance of anoxic and facultative ponds in Jordan was investigated for 12 months. Calculated values of the first order kinetic equation rate for CBOD removal (KCBOD) has resulted in different KCBOD's for different ponds in the same month, at the same temperature. It is evident that factors other than temperature must influence values of KCBOD. The KCBOD values determined were generally lower than those reported in the literature. The maximum value found was only 0.16 (/day). A pond was emptied after 18 months of operation and sediment was found randomly distributed over the pond area, with a depth ranging from 2 to 6 cm (averaging = 4 cm). A simple model has been established to estimate sediment depth (Hs in cm) in terms of the operating time in months (t).

Natural treatment systems

Natural treatment systems

Removal of priority organic pollutants in stabilization ponds

Based on screening priority pollutants in the Tianjin area, this paper has selected some environmentally significant organic pollutants, including alkylbenzenes, chlorobenzenes, naphthalene, 666, etc., and reported on their removal efficiences in the laboratory and outdoor strengthened facultative stabilization ponds. The possible transport pathway of the pollutants was studied. Results showed that the removal efficiencies of most pollutants are satisfactory. Dissolved oxygen (DO) in the pond had a great impact on the efficiency. Pollutants could be removed from water by adsorption on suspended substances.

Mechanistic model for facultative stabilization ponds

ABSTRACT: In this work a 12‐parameter mechanistic model representing the biochemical interactions in facultative stabilization ponds is proposed (as an extension of the Fritz et al. [ 1979] model). An acceptable degree of fitness between the model predictions and the experimental data from the real plant was obtained. The stability of calculated concentrations with respect to small changes in the kinetic constant values of the model were also studied.

A tracer study of the hydraulics of facultative stabilization ponds

The hydraulic behavior of wastewater stabilization ponds operating in different regions in Spain has been investigated using a stimulus-response technique. A tracer, tritiated water, was injected at the entrance of each one of the facultative ponds at five facilities. The resulting time distribution functions were used to calculate the mean hydraulic residence time and the extent of short-circuiting inside the ponds. The percentage of dead volume ranged from 10 to 42%. Treatment efficiency would thus be substantially improved by correcting these large dead volumes. The inlets and outlets of the ponds have been redesigned and are being rebuilt as remedial measures to this problem. The statistical analysis of the results indicates that the completely stirred tank reactor model can be used to represent the hydraulic behavior of all the ponds studied, at a 99% confidence level.

Aeration and Water Hyacinths in Waste Stabilization Ponds

The investigation was based on two facultative stabilization ponds initially designed to operate in parallel, and now receive wastewater in excess of their capacities from a fast expanding housing estate in the Caribbean Island of Trinidad. Because of the deterioration of the effluent quality relative to acceptable standards, an attempt was made to upgrade the ponds using water hyacinths at the early stages. However, from the results, it was clear that the introduction of water hyacinths in the test pond did not lead to any substantial improvement in the effluent because of the high loading on the pond. Therefore the ponds were modified to operate in series with surface aerators installed in the first pond. Initially, the effluent quality was monitored in terms of total suspended solids, volatile suspended solids, biochemical oxygen demand, faecal coliform bacteria, pH and dissolved oxygen with aeration in the first pond and no aquatic plants in the second pond. Although there was a significant improvement in the effluent quality, the values remained above the standards. As a result, water hyacinths were introduced in the second pond and the effluent quality monitored together with aeration in the first pond. The effluent quality improved with total suspended solids and biochemical oxygen demand values both as low as 10 mg/l in certain months, but additional treatment was needed to reduce faecal conforms.