Wastewater Stabilization Ponds Research Articles

Modeling and Optimizing Wastewater Stabilization Ponds for Domestic Wastewater Treatment

In Wastewater Stabilization Ponds (WSPs), baffle walls (BWs) have the dual benefit of reducing area requirements and increasing contaminant removal efficiency up to a certain threshold. However, this advantage is mitigated by the increased demand for construction materials, highlighting the need for optimization. Effectively optimizing WSPs to suit diverse climatic regions can substantially alleviate nationwide wastewater treatment challenges. This study focuses on optimizing WSPs across seven distinct climatic regions in Turkey. In the initial phase, a comprehensive analysis was conducted using design spreadsheets for the WSPs to determine the best configuration based on traditional methodology (TM). The results demonstrated a significant decrease in WSPs area and hydraulic retention time (RT), validating the effectiveness of BWs provision. However, this approach requires additional time and effort. Subsequently, mathematical modeling (MM) was used to further reduce the time required for the optimization process. Using the interior-point algorithm in MATLAB and the generalized reduced gradient (GRG) algorithm in MS Excel Solver, both algorithms within MM effectively decreased the WSPs area and RTby approximately 10%, while decreasing the required concrete volume by approximately 5% compared with TM. As other algorithms may yield better optimization, they can be investigated by developing specialized software for WSPs. Doi: 10.28991/CEJ-2023-09-11-014 Full Text: PDF

Evaluation of a Three-Dimensional Hydrodynamic and Water Quality Model for Design of Wastewater Stabilization Ponds

A three-dimensional coupled hydrodynamic and water quality model (Deflt3D-WAQ) was applied to evaluate the ability of a computational simulation to reproduce seasonal water quality conditions over a seven-month period in a wastewater stabilization pond located in eastern Ontario, Canada. Trends in effluent nutrient concentrations, pH, and dissolved oxygen were visually reproduced, and root-mean square errors, in comparison with weekly observations (alkalinity, 43 gHCO3 m−3; dissolved oxygen, 4.0 gm−3; NO3, 2.2 gN m−3; PO4, 0.10 gP m−3; NH4, 0.14 gN m−3; pH, 0.65), were consistent with literature values. Three phytoplankton groups (green algae, diatoms, and flagellates) were also simulated. The calibrated model was extended to investigate the effects of changes in pond design on treatment efficiency, including removing the baffle, increasing the pond depth, increasing wind sheltering, and relocating the influent pipe from the pond bottom to the surface. Increasing the pond depth and wind sheltering reduced vertical mixing, sequestering nutrients near the sediments and improving effluent water quality. Removing the baffle had no impact on removal efficiency, and relocating the inlet to the surface reduced pond efficiency. Three-dimensional biogeochemical models thus provide a virtual process-based means for testing pond prototype design.

Eichhornia crassipes-rhizospheric biofilms contribute to nutrients removal and methane oxidization in wastewater stabilization ponds receiving simulative sewage treatment plants effluents

Wastewater stabilization ponds (WSPs) have been used in treating sewage treatment plants (STPs) effluents. However, little is known about the role of rhizospheric biofilms on methane release in WSPs with floating plants. In the present study, the nutrient removal, CH4 fluxes, CH4 oxidization potential and rhizospheric bacterial community were investigated in WSPs with Eichhornia crassipes under simulate STPs effluents for 31 days. At the end of the experiment, E. crassipes biomass was 5.60–8.81 times of initial weight and increased with increasing nutrients concentration. E. crassipes effectively reduced methane release and nutrients. Compared to control, E. crassipes reduced 52.30%–83.21% of CH4 fluxes at water-atmosphere interface and had better inhibition effect on CH4 fluxes in treatments with high nutrients. However, methane oxidization rates of E. crassipes roots were higher in low nutrients (0.83 ± 0.046 mg CH4 (kg fresh plant)−1 day−1) than high nutrients (0.12 ± 0.04 mg CH4 (kg fresh plant)−1 day−1). Structural equation modeling revealed that biomass of E. crassipes has negative effect on CH4 fluxes (−0.453, p = 0.000). Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi and Actinobacteria were the predominant phyla in the rhizospheric biofilm of E. crassipes and contributed to nutrients removal. Aerobic methanotrophs and pomA abundances were higher in rhizospheric biofilm exposed to high nutrients than low nutrients and aerobic methanotrophs had close interactions with other microorganisms and participated in the carbon and nitrogen cycle, demonstrating that many bacteria harboring pmoA gene did not fully involve in methane oxidization. These data highlight plants E. crassipes have an important role in both reducing methane release and nutrients removal.

Mathematical modeling and optimization of wastewater stabilization ponds using nonlinear programming

This research work proposes a mathematical optimization model for constructing two ponds (1. Facultative pond and 2. Maturation pond) provided in series. The model uses concrete volume as its objective minimization function. There were two decision variables; the first was the detention time (DT) and the second in the list was the number of provided baffle walls (NBW) in both ponds. The constraint parameters include fecal coliforms and biochemical oxygen demand (BOD5). The model was applied with the help of an Add-Ins of MS Office: Excel solver. The generalized reduced gradient algorithm was utilized in the solver (GRG). Before applying the mathematical optimization model, ponds were designed with the conventional method and then using optimized values of the variables. A comparison of the findings reveals that a 13.79 percent reduction in the DT, an 11.55 percent reduction in the area, and a 7.19 percent reduction in the volume of concrete occurred. The reduction values mentioned above are significant since these systems' fundamental drawback is the area's requirement. In addition, sensitivity analyses of the objective function and the removal of pollutants are also provided. The model described above is sensitive to variations in the parameters. Both analyses demonstrated that the effluent characteristics comply with the class-B irrigation standards in Turkey. It is advised to do more optimization studies for WSPs with the help of other algorithms and tools available in the literature for distinct wastewater treatment plants.

Evaluation of the Richness, Species Diversity, and Biosafety of Saprotrophic Fungal Communities in Constructed Wetlands and Biological Wastewater Ponds

The present study was focused on the characterization of the biocenotic diversity of saprotrophic fungi, taking into account the impact of various treatment systems and technological stages as well as the physicochemical properties of wastewater. The biodegradation potential, the hazard posed to humans, animals, and the environment, and the effectiveness of elimination of propagules were evaluated. The most effective elimination of fungal propagules was recorded in hybrid constructed wetland systems with horizontal (HF-CW) and vertical (VF-CW) wastewater flow, especially in the VF-HF objects. The fungal communities present in wastewater from small constructed wetland (CW) and wastewater stabilization ponds (WSP) were dominated by ubiquitous terrestrial molds accompanied by a minimal number of yeasts. The similarity of the species composition of the fungal communities between the treatment plants was generally low, whereas the species diversity together with the population size was very high at the various stages of wastewater treatment. Species with potential pathogenicity to humans and animals accounted for over 45%, i.e., were classified as BioSafety Level 1 and 2 (BSL-1 and BSL-2 groups), and potentially phytopathogenic fungi represented 31.5% of the mycobiota species composition. The dynamics of fungal growth were correlated with the content of organic pollutants and nutrients (nitrogen and phosphorus) and with oxygen deficiency. The accumulation of nitrates corresponded to the decline in the frequency of fungi in treated wastewater. The lowest efficiency of the removal of fungi was exhibited by the biological wastewater stabilization ponds.

Optimizing the amount of concrete for the construction of wastewater stabilization ponds: A case study of Ayvadere, Trabzon, Türkiye

Natural systems are a cost-effective way to clean wastewater from small communities. This paper aims to use an optimization technique to minimize the volume of concrete needed to construct a facultative pond provided within a series of three ponds. A nonlinear constrained optimization model was written and then solved using one of the Add-Ins of MS office. The add-in used was Excel Solver, and the algorithm was generalized reduced gradient (GRG). Before applying the optimization model, wastewater stabilization ponds (WSPs) were de-signed using various configurations and arrangements. The best possible configuration that gave minimum area and hydraulic detention time was selected for the study area. Afterward, the optimization model was applied that further reduced the area by 11.46 %, hydraulic detention time by 11.47%, and concrete volume by 6.94% compared to the traditional approach. In both methods, effluents satisfy the Turkish class-B stand-ards for irrigation. It is recommended that a small-scale application of the model be made to compare the results before applying it on a large scale.

Investigating the efficiency of Vertical Sub-Surface Flow Constructed Wetlands in the Reduction of Faecal Indicator Bacteria and Organic matter Under Varied Sizes of Gravel Substrate Aggregates

Constructed wetlands (CWs) polish wastewater prior to discharge into aquatic receptacles. Size variabilities of substrates used in CWS may have effects on the treatment efficiencies though there is scanty information regarding this aspect in VSSF CWs. To address this knowledge gap, a laboratory scale mesocosm experiment was set up to investigate the potential of a VSSF CW to reduce organic matter and FIB using various gravel substrate aggregate sizes. This consisted of three gravel size treatment units; <12.5, 12.5-18 and 18-24 mm in triplicates. 70 liters of pre-treated wastewater from the final wastewater stabilization pond (WSP) of Egerton University’s WSPs system was added to the units, allowed to settle for 6 weeks for development of biofilms, followed by periodic feeding of equal wastewater quantity on weekly basis and influent and effluent samples collected for 8 weeks for analysis. Results disclosed reduction efficiency of 95.2, 94.3 and 88.4 % for E coli in the fine, medium and coarse gravel aggregates respectively. Less than 20 % reduction efficiency was recorded for BOD5 in all gravel aggregate sizes. There was no significant variation on performance of the three gravel aggregate sizes in reduction of both FIB and BOD5 (p˃0.05). Poor performance in BOD5 reduction was related to absence of wetland macrophytes in the study. The relatively high reduction efficiency for FIB was attributed to other factors and processes such as predation, mechanical interactions, starvation, microbial interactions and natural die-offs. The study recommends assessing the combined effect of increasing the retention time, use of wetland macrophytes and incorporating various gravel aggregate sizes in order to increase the efficiency of VSSF CW in reduction of FIB and organic matter.

Identification of key microorganisms in facultative stabilization ponds from dairy industries, using metagenomics.

Wastewater stabilization ponds are a natural form of wastewater treatment. Their low operation and maintenance costs have made them popular, especially in developing countries. In these systems, effluents are retained for long periods of time, allowing the microbial communities present in the ponds to degrade the organic matter present, using both aerobic and anaerobic processes. Even though these systems are widespread in low income countries, there are no studies about the microorganisms present in them and how they operate. In this study, we analised the microbial communities of two serial full-scale stabilization ponds systems using whole genome shotgun sequencing. First, a taxonomic profiling of the reads was performed, to estimate the microbial diversity. Then, the reads of each system were assembled and binned, allowing the reconstruction of 110 microbial genomes. A functional analysis of the genomes allowed us to find how the main metabolic pathways are carried out, and we propose several organisms that would be key to this kind of environment, since they play an important role in these metabolic pathways. This study represents the first genome-centred approach to understand the metabolic processes in facultative ponds. A better understanding of these microbial communities and how they stabilize the effluents of dairy industries is necessary to improve them and to minimize the environmental impact of dairy industries wastewater.

Transport behavior and risk evaluation of pharmaceutical contaminants from Swaswa Wastewater Stabilization Ponds | JBES 2022

Transport behavior and risk evaluation of pharmaceutical contaminants from Swaswa Wastewater Stabilization Ponds | JBES 2022

Impacts of Nutrients Loading on Methane Release in Wastewater Stabilization Ponds with Eichhornia Crassipes

Impacts of Nutrients Loading on Methane Release in Wastewater Stabilization Ponds with Eichhornia Crassipes

Assessment of sediment arsenic and iron occurrence and leaching potential in a potable water treatment plant wastewater stabilization pond system

Wastewater stabilization ponds (WSPs) are commonly used to reduce wastewater metal(loid) concentrations from drinking water treatment plants (DWTPs) through sedimentation. However, this results in increased sediment concentrations that can be released back into the overlying water. Thus, our goal was to evaluate the WSP metal(loid)s occurrence and leaching potential. Currently, a Saskatchewan based DWTP’s WSP system was investigated given historically elevated effluent As and Fe concentrations. The WSP consists of five ponds that were sampled on six occasions in 2019 and 2020. In addition, sediments were used in laboratory-based experiments to determine their leaching potential. Overall, the sediments were found to contain elevated concentrations of As and Fe of 25 to 400 mg/kg and 10 000 to 45 000 mg/kg, respectively. Leaching experiments indicated that the pond sediments could potentially release As and Fe with log Kd values ranging from 2.21 to 4.31 L/kg, whereas Fe ranged from 3.32 to 5.53 L/kg.

Assessment of a wastewater stabilization pond system for removal of arsenic, iron, and ammonia from reverse osmosis water treatment plant residual wastewater

Drinking water treatment plants (DWTPs) produce wastewaters with elevated concentrations of heavy metals, metalloids, ammonia, and other contaminants. These wastewaters require treatment via processes including wastewater stabilization ponds (WSPs). This study assessed the arsenic (As), iron (Fe), and ammonia (NH3) concentrations in a Saskatchewan DWTP WSP system of five sequential ponds. Drone imaging combined with flow and depth data was used to estimate retention times which increased from 7–9 to 8–10 days after the DWTP upgrade. Concentration trends showed Fe decreased from Pond 1 to 3 and increased in Ponds 3 and 5, while As decreased from Pond 1 to 5. Average effluent As concentrations of 10.6 µg/L were above the 5.0 µg/L guideline, while concentration guidelines for both Fe and NH3 were easily met post-upgrade in 2020. Several actions are recommended to ensure adequate WSP operation including dredging, aeration, and installing macrophytes capable of As uptake.

Are Rural and Small Community Aerated Wastewater Stabilization Ponds a Neglected Source of Microplastic Pollution?

Wastewater treatment systems collect and treat sewage that includes microplastics (MPs). However, we are not aware of any studies on the occurrence and distribution of MPs in wastewater stabilization ponds (WSPs), which serve small communities worldwide. Here, we characterized MPs (~45 µm–5 mm) in an aerated WSP serving ~500 houses and an adjacent lake. Putative MPs were most abundant in duckweed (Lemna minor) and sludge (75 ± 22 and 12.8 ± 3.1 particles/g, respectively: ±1 standard deviation (SD), n = 6, dry weight). In the water, average concentrations (particles/L ± 1 SD, n = 6) were highest in the pond (4.1 ± 0.6), followed by effluent (3.9 ± 0.5) and the lake (2.6 ± 0.6). Over 20 types of MPs were identified in each different compartment, with the distribution varying somewhat between the water, sludge, and duckweed. Polyester and polyethylene were the predominant types, followed by polyethylene terephthalate, polyacrylate, polyvinyl chloride, polystyrene, and others. Morphologies consisted of fibers (62–71%), fragments (28–37%), and beads (1–6%). High-density polymers were more frequently found in sludge. Potential sources of the MPs include synthetic textiles from laundry and other plastics washed down household drains. Overall, with ~786,000 MPs/day released in the pond effluent and with duckweed a source of food for waterfowl, we demonstrate that WSPs can be point sources of MPs to both aquatic and terrestrial ecosystems and thus deserve further scrutiny.

Annual Variation in the Performance of Settat Wastewater Stabilization Ponds Located in Settat City, Morocco

Annual Variation in the Performance of Settat Wastewater Stabilization Ponds Located in Settat City, Morocco

Changes in Bacterial Communities During Treatment of Municipal Wastewater in Arctic Wastewater Stabilization Ponds

Wastewater stabilization ponds (WSPs) are commonly used to treat municipal wastewater in the Canadian Arctic. Bacterial community structure and functionality remain mostly uncharacterized for arctic WSPs, yet are presumed important for treatment outcomes during the 3-month summer treatment season with open water in the WSPs. The objective of this study was to investigate treatment performance and related temporal and spatial changes in the structure and putative function of bacterial communities during treatment of municipal wastewater in the WSPs of Pond Inlet and Clyde River, Nunavut over two consecutive summer treatment seasons. Influent raw wastewater contained a high organic load and large bacterial communities (~9 log 16S rRNA copies/mL) belonging mainly to Proteobacteria. Although designed to be facultative ponds, both WSPs remained anaerobic with neutral pH values (7.5–7.8) throughout the summer treatment season. Water quality data showed that nutrients [measured as carbonaceous biological oxygen demand (CBOD5)], total suspended solids, and total ammonia nitrogen were progressively reduced during treatment in the ponds as the summer progressed. The pond bacterial population size and species richness depended on the pond temperature (2–18°C), with 8.5 log 16S rRNA copies/mL and the largest alpha diversities (Shannon-Wiener index of 4-4.5) observed mid-season (late July). While the phylogenetic beta diversity in raw wastewater from the two locations remained similar, pond bacterial communities underwent significant (p < 0.05) changes to dominance of Comamonadaceae, Geobacteracea, and Porphyromonadaceae. Multivariate distance based redundancy analysis and predicted gene functionalities in the microbiota agreed with water quality results that microbial removal of nutrients (e.g., CBOD5) peaked in the middle of the summer coinciding with the treatment period with the highest pond temperatures. Information from this study will be useful for further development of models to predict biological treatment outcomes, which could be used to size and assess the feasibility of WSPs in extreme climates. Higher pond temperatures resulted in optimal biological processes and nutrient removal in the middle of the summer. While it is challenging to control environmental factors in a passive wastewater treatment system there are some design considerations that could be used to optimize temperature regimes, such as the depth of the pond.

Determination of Heavy Metals in Groundwater Around Al-Buraihi Sewage Station in Taiz City, Yemen.

Background.In recent years, mitigation of groundwater contamination resulting from the limited availability of freshwater for domestic use has become an important issue. The presence of heavy metals in water could have adverse effects on both plant and animal life.Objectives.The main objective of the present study was to determine possible heavy metal contamination in groundwater around Al-Buraihi sewage station in Taiz, Yemen and to understand possible sources of contamination and their relationships with groundwater.Methods.Wastewater samples were collected from a wastewater stabilization pond from Al-Buraihi sewage station and borewell water samples were collected from the vicinity. The presence of heavy metals was quantified using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation test was performed to understand the relationship between wastewater and groundwater samples.Results.Physical variables including pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature and elements such as silver (Ag), arsenic (As), aluminum (Al), barium (Ba), boron (B), cadmium (Cd), chromium (Cr), iron (Fe), molybdenum, nickel (Ni), selenium (Se) and zinc (Zn) exceeded the permissible limits recommended by international standards in wastewater samples.Conclusions.Treated sewage wastewater in the study area is not suitable for irrigation as the elements/heavy metals are accumulated in soil and plants and may be accumulated in humans and animals through bio-accumulation. In addition, these heavy metals reach the water table and aquifers through percolation, thereby polluting groundwater.Competing Interests.The authors declare no competing financial interests.

Assessment of performance of wastewater stabilization ponds using faecal indicator bacteria reduction efficiency in a tropical environment

Egerton University (EU) uses Wastewater Stabilization Ponds (WSPs) for wastewater treatment. An adjoining wetland with gravel bed substrate and freesurface flow meant to polish discharge before releasing into River Njoro is currently non-operational. The current study aimed at establishing the performance of WSPs in terms of concentration and reduction efficiencies of Faecal Indicator Bacteria (FIB); Total Coliforms (TC) and Escherichia coli (E. coli). Wastewater samples were collected weekly for one month from mid- November to mid-December 2017. Total Coliforms and E. coli were isolated using selective and differential media following Membrane Filtration (MF) method. Colonies were cultured on Chromocult Coliform Agar (CCA) and enumerated using standard procedures for examination of water and wastewater. The results were expressed as Colony Forming Units (CFUs) per 100 ml of the original sample. The inlet showed highest concentration of FIB which reduced along the treatment pathway. Total Coliforms and E. coli ranged between 2.5 × 108 - 2.9 × 1011 and 5.9 × 105 - 1.8 × 1010 CFUs/100 ml respectively with cumulative reduction efficiencies between 2 to 4 log units for E. coli and 2 to 3 log units for TC in the two maturation ponds. Although concentration of FIB in EU WSPs reduces along the treatment pathway, the effluent quality is above recommended international standards for discharge into surface waters. The trend is attributed to lack of frequent monitoring, insufficient maintenance, together with short- circuiting effect due to by-passing of wastewater in the design of the new pond system.

Behavior and Removal of Ciprofloxacin and Sulfamethoxazole Antibiotics in Three Different Types of Full-Scale Wastewater Treatment Plants: A Comparative Study

Due to the inadequate removal rates of drug residues in wastewater treatment plants (WWTP), the transition of these compounds into the environment has become a serious environmental problem for ecosystems and public health. In this study, occurrence, fate, and removal of widely consumed two antibiotics, ciprofloxacin (CIP) and sulfamethoxazole (SMX), selected from fluoroquinolone and sulfonamide groups, respectively were investigated in three different types of full-scale WWTPs located in Turkey. In this context, three WWTPs consisting of advanced biological treatment (large-scale), wastewater stabilization pond (WSP) (medium-scale), and constructed wetland (CW) (small-scale) were selected. While the detected influent concentrations of CIP in WWTPs ranged between the 218.6 and 2733.5 ng/L, maximum influent concentration for SMX in the same plants was determined as 179.7 ng/L. On the other hand, although it was detected at higher concentrations in raw wastewater, CIP was significantly removed in all WWTPs with a removal efficiency ranging from >77.1 to >98.2%. However, SMX showed quite different behaviors depending on the applied wastewater treatment processes in WWTPs in terms of total removal achieved. While treated in WSP well enough (>72.2%), a serious negative removal efficiency (−133.4%) was achieved for SMX in the WWTP having advanced biological treatment. Best removal performance obtained for the both antibiotic compounds among the investigated WWTPs was the medium-scale WSP consisting of anaerobic and facultative stabilization ponds, consecutively. This situation also supported the idea that WWTPs which are operated with higher solid retention time (SRT) and hydraulic retention time (HRT) contribute positively in the removal of antibiotic compounds.

Comparison of advanced biological treatment and nature-based solutions for the treatment of pharmaceutically active compounds (PhACs): A comprehensive study for wastewater and sewage sludge.

Passing of pharmaceutical residues into environment in an uncontrolled manner as a result of continuous increase in drug consumption across the globe has become a threatening problem for the ecosystems and almost all living creatures. In this study, diclofenac (DCF), carbamazepine (CBZ), 17β-estradiol (17β-E2) and 17α-ethynylestradiol (EE2) belonging to different therapeutic classes were investigated simultaneously in advanced biological treatment and nature-based treatments during 12-months sampling campaign. In this context, behavior patterns of pharmaceutically active compounds (PhACs) throughout the both wastewater and sludge lines in advanced biological wastewater treatment plant (WWTP), wastewater stabilization pond (WSP) and constructed wetland (CW) were discussed in detail based on each treatment processes seasonally. Furthermore, statistically evaluated data obtained in full-scale WWTPs were compared with each other in order to determine the valid removal mechanisms of these pharmaceutical compounds. While DCF and CBZ were detected very intensively both in the wastewater and sludge lines of the investigated WWTPs, steroid hormones,17β-E2 and EE2, were determined below the LOQ value in general. Annual average removal efficiencies achieved in studied WWTPs for DCF ranged between -23.3% (in CW) and 75.2% (in WSP), while annual average removal rates obtained for CBZ varied between -20.7% (in advanced biological treatment) and 10.0% (in CW). It has been found that DCF was highly affected by different wastewater treatment processes applied in the WWTPs compared to CBZ which showed extraordinary resistance to all different treatment processes. Although calculated in different rates for each compounds, biodegradation/biotransformation and sorption onto sewage sludge were determined as the main removal mechanisms for PhACs in plants. Although showed a similar behavior in the sludge dewatering unit (decanter) present in the advanced biological WWTP, quite different behaviors observed in the anaerobic digester for DCF (up to 15% decrease) and CBZ (up to 95% increase). Sorption and desorption behaviors of DCF and CBZ were also evaluated in the sludge treatment processes found in advanced biological WWTP. Percentages of originated extra annual average of pharmaceutical loads were calculated as 0.64% and 0.90% for DCF and CBZ, respectively in the advanced biological WWTP due to the sidestream caused by the sludge dewatering unit.

Implementation of fuzzy optimization approach to facultative wastewater stabilization ponds problem considering fuzzy parameters

This article proposed a decision-making tool in the form of a fuzzy programming approach to be used in determining the optimal decision on facultative stabilization ponds in a wastewater treatment facility. The specific problem was approaching the uncertain inflow rate of the wastewater to the pond as a fuzzy variable and this required the formulation of a mathematical optimization model containing the variables which was solved using fuzzy programming to achieve the optimal load of the wastewater and corresponding storing time as the optimal decision. Moreover, a numerical experiment was conducted using secondary and data generated from observing the Sewon wastewater treatment facility located in Yogyakarta, Indonesia containing four facultative ponds. The results produced the optimal decision with the wastewater load for each pond found to be 1199.5 kg while the corresponding storing time was 0.23, 0.23, 0.79, and 0.71 day for the pond I, II, III, and IV respectively.