Stabilization Ponds Research Articles

Utilising Constructed Wetlands From Water Hyacinth for Wastewater Treatment in Oxidation Ponds

Constructed wetlands are engineered to duplicate the processes occurring innaturalwetlands. Themain purpose of the structure is to remove contaminants or pollutants from wastewater. Constructed wetland is a new, creative, cost-effective, and green technology compared to conventional treatment systems. Water hyacinth couldbe cultivated for wastewater treatment and utilised to aid the purification of either industrial wastewater or sewer water. Consequently, the present study was conducted to determine the effects of constructing wetlands with water hyacinth on the wastewater quality of an oxidation pond and the cultivation of water hyacinth as constructed wetlands in an oxidation pond. Floating cages containing water hyacinth plants were monitored for two phasesunder different wastewater parameters. The data were compared to the Malaysian prescribed Sewage and Industrial Effluent Discharge Standards. The water hyacinth constructed wetlands produced a positive impact and met the requirements for effluent discharge standards.

Long-term effects of duckweed cover on the performance and microbial community of a pilot-scale waste stabilization pond

Duckweed-based ponds (DP), as a modified type of waste stabilization ponds (WSP) are receiving growing attention due to the sustainable production of high-quality duckweed biomass. However, the comprehensive effects of duckweed cover on nutrient removal, greenhouse gas emission and microbial community of the WSP have rarely been studied. In this study, two pilot-scale WSP (12 m2) with (DP) and without (OP) a duckweed mat on the surface were compared over 1 year to determine the effects. The results showed that, compared to OP, DP had higher TP, but lower TN and NH4+-N removal efficiencies, and lower pH, dissolved oxygen (DO) and sedimentation rate of settling detritus. For both nitrogen and phosphorus removal, the dominant pathway was duckweed uptake (66.95% and 93.18%, respectively) in DP; however, it became other pathways (mainly nitrification/denitrification, 82.27%) and sedimentation (87.65%), respectively, in OP. Meanwhile, DP had lower N2O, but higher CH4 emission fluxes than OP, resulting in comparable global warming potential between OP and DP (approximately 2800 g CO2/m2/yr). Microbial community analysis indicated that the greater nitrogen removal and N2O emission in OP could be attributed to higher abundance of ammonia-oxidizing bacteria in the water and denitrifiers in the sediment, supported by higher DO and settling organic carbon, respectively. Meanwhile, the greater CH4 emission in DP could be attributed to higher abundance of methanogens and syntrophic methanogenic bacteria in the sediment. Thus, despite favourable effects on nutrient recovery and phosphorus removal mainly attributed to duckweed uptake, duckweed cover had unfavourable effects on nitrogen removal and CH4 emission reduction of the WSP mainly attributed to microbial taxa which were influenced by environmental conditions (such as DO and settling detritus) in the WSP. These findings help to clarify the influencing mechanism of duckweed cover, providing overall insight into the function and application of the DP.

Research Progress on Integrated Treatment Technologies of Rural Domestic Sewage: A Review

The improvement of rural living standards in developing countries and the continuous upgrading of the rural industrial economy have prompted the diversification of rural areas and residential forms. Thus, an integrated rural sewage treatment process has gradually become the mainstream technology for rural sewage treatment. Numerous studies have reported the effects of ecological wastewater treatment. Meanwhile, the relevant process technologies, evaluations, and operating models of the integrated rural sewage treatment process have yet to be thoroughly summarized. This review aims to fill these gaps. First, the applicability of artificial wetland, soil infiltration, stabilization pond, and integrated rural sewage treatment process technology in rural sewage treatment are outlined and compared. Second, the process flow, technical characteristics, and economic indicators of typical integrated sewage treatment processes (i.e., Anoxic/Oxic (A/O) process, Membrane Bio-Reactor (MBR) process, biological contact oxidation process, Sequencing Batch Reactor Activated Sludge (SBR) process) are introduced. The engineering application effects of the integrated rural sewage treatment process in different countries are also described. Third, the practical and effective evaluation methods of the integrated rural sewage treatment process are introduced. Bearing in mind the current operation and maintenance management modes of the integrated rural sewage treatment process in developed and developing countries, combined with the national conditions of developing countries, the prospect section provides development proposals for further optimization and improvement of the integrated rural sewage treatment process in developing countries.

Social–Ecological Impact Assessment and Success Factors of a Water Reuse System for Irrigation Purposes in Central Northern Namibia

With regard to water supply constraints, water reuse has already become an indispensable water resource. In many regions of southern Africa, so-called waste stabilisation ponds (WSP) represent a widespread method of sewage disposal. Since capacity bottlenecks lead to overflowing ponds and contamination, a concept was designed and piloted in order to upgrade a plant and reuse water in agriculture. Using a social–ecological impact assessment (SEIA), the aim of this study was to identify and evaluate intended and unintended impacts of the upgrading of an existing WSP to reuse water for livestock fodder production. For this purpose, semistructured expert interviews were conducted. In addition, a scenario analysis was carried out regarding a sustainable operation of the water reuse system. The evaluation of the impacts has shown that intended positive impacts clearly outweigh the unintended ones. The scenario analysis revealed the consequences of an inadequate management of the system and low fodder demand. Furthermore, the analysis showed that good management of such a system is of fundamental importance in order to operate the facility, protect nature and assist people. This allows subsequent studies to minimize negative impacts and replicate the concept in regions with similar conditions.

Removal of Pharmaceuticals in a Macrophyte Pond-Constructed Wetland System and the Effect of a Low Effluent Recirculation

Waste stabilization ponds and constructed wetlands (CWs) are effective at eliminating pharmaceutical residues, but removals are not usually complete. Their combination is regarded as an efficient, robust wastewater treatment method, but their efficiency in the removal of pharmaceuticals and the effect of a mild effluent recirculation has not been sufficiently studied in full-scale systems. Effluent recirculation can help to improve performance by increasing hydraulic residence time and, eventually, dissolved oxygen concentration. In this work, the presence of pharmaceuticals in wastewater from a university campus, their removal in a macrophyte pond–CW system, and the effect of effluent recirculation on removal and ecological risk were evaluated. Stimulants (caffeine and nicotine) and non-steroidal anti-inflammatories (naproxen and ibuprofen) were the most detected compounds in the influent and showed the highest concentrations, ranging from 0.5 to 300 µg·L−1. The pond–CW combination showed notable elimination for these compounds, achieving 87% on average. The ecological risk was also reduced by between 5.5 and 12.4 times, but it was still over values that indicates high ecological risk, mainly because of the concentrations of nicotine and ibuprofen. The effect of effluent recirculation was not as high as expected since the removals of caffeine, paraxanthine and naproxen were significantly improved, but those of atenolol and ibuprofen were lower. These results suggest that a higher recirculation ratio should be tested.

Bacterial Proliferation Reduces Sulphur Toxicity in Stabilization Ponds: Safer Water Resources by Photosynthesis

Background: Studies suggest that sulfur may react with plants or monocellular organisms, such as fungi, to produce toxic agents. It has been theorized that sulfur enters cells and affects their respiration. This study reports on a phototroph development that leads to the diminution and/or production of sulfur and release of hydrogen sulfide from public ponds. Methods: This study was conducted in anoxic stabilization ponds at a dimension of 1×0.25×1 (m), with a hydraulic retention time of 6 days. The ponds’ water was tested during the dark and light cycles. The experiments were carried out by factorial design and measured three variables: volumetric organic loading, sulphate concentrations and temperature. Results: Cyanobacteria and Rhodobacter species were the most abundant phototroph cellular organisms. The mean value of total sulfur and un-ionized hydrogen sulfide concentration were 74 mg/L and 21 mg/L, respectively, at the volumetric organic loading of 100 g BOD5/m3 per day. The efficiencies of biochemical and chemical oxygen removal were 71.9% and 59.1%, respectively. The mean proliferation rate of photosynthetic sulfur bacteria was 3.4×106 cells/ml. Conclusion: photosynthetic sulfur bacteria significantly reduced the sulfur concentration generated in the ponds. The illumination of bright light enhanced the sulfur reduction by the photosynthetic sulfur bacteria in the wastewater of the anoxic stabilization ponds.

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

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

Heavy metal remediation from wastewater using microalgae: Recent advances and future trends

Microalgae-based wastewater treatment has previously been carried out in huge waste stabilization ponds. Microalgae, which can absorb carbon dioxide while reusing nutrients from sewage, has recently emerged as a new trend in the wastewater treatment business. Microalgae farming is thought to be a potential match for the modern world's energy strategy, which emphasizes low-cost and environmentally benign alternatives. Microalgae are being used to treat wastewater and make useful products. Microalgae, for example, is a promising renewable resource for producing biomass from wastewater nutrients because of its quick growth rate, short life span, and high carbon dioxide utilization efficacy. Microalgae-based bioremediation has grown in importance in the treatment of numerous types of wastewater in recent years. This solar-powered wastewater treatment technology has huge potential. However, there are still issues to be resolved in terms of land requirements, as well as the process's ecological feasibility and long-term viability, before these systems can be widely adopted. Due to cost and the need for a faultless downstream process, it is difficult to deploy this technology on a large scale. Other recent breakthroughs in wastewater microalgae farming have been investigated, such as how varied pressures affect microalgae growth and quality, as well as the number of high-value components produced. In this review, the future of this biotechnology has also been examined.

Numerical modelling of hydraulic efficiency and pollution transport in waste stabilization ponds

This paper investigates the hydraulic performance and solute transport processes in waste stabilization ponds (WSPs). A numerical model comprised of Reynolds-averaged Navier–Stokes (RANS) flow hydrodynamic model with the standard k − ε turbulence closure coupled with the advection-diffusion solute transport model, is developed in a three-dimensional Cartesian coordinate system. The proposed numerical model is successfully validated against laboratory-scale physical modelling measurements of flow hydrodynamics and solute characteristics across trapezoidal pond geometry. The developed numerical model is adopted to run series of scenario-based simulations to investigate the effects of WSP's geometrical features and implementation of an island retrofitting on the hydraulic performance and treatment efficiency of the WSPs. Fifteen pond configurations with varying side-walls slope and island configurations are simulated. Vertical and horizontal structures of flow hydrodynamics across the pond are investigated. Solute transport processes are studied through determining residence time distribution (RTDs) curves based on numerical tracer simulations. Two deflector island configurations (parallel and rotated) are simulated to investigate their influence on enhancing the hydraulic performance of the WSP. The analysis of the numerical results indicates an overall positive impact of deflector island retrofitting on the hydraulic performance of the WSP. The side-walls slope are shown to play a key role in determining the overall performance of the WSP. For the cases with side-walls slope of 1:1, 0.5:1 and 0:1, the hydraulic efficiency of the WSP was enhanced by adding both parallel and rotated islands. However, for the cases with side-walls slope of 2:1 and 1.5:1, addition of island deflector is shown to have negative impacts on the hydraulic performance of the waste stabilization pond.

Treatment of waste stabilization pond effluent using natural zeolite for irrigation potential.

Direct utilization of treated effluent from natural treatment systems for irrigation can be challenging on sensitive plants due to high levels of salinity. Post-treatment of such an effluent prior to its applicability in irrigation can be of significant importance. In this study, the wastewater from a natural treatment plant was treated using a lab-scale filtration system with zeolite as a filter material. Three different column depths (0.5 m, 0.75 m, and 1 m) were used to investigate the effect of column depth on the treatment efficiency of the media. The suitability of the raw wastewater and the treated effluent from each column for irrigation purposes was investigated. The water quality parameters investigated were; electrical conductivity (EC), total dissolved solids (TDS), sodium (Na+), calcium (Ca2+), and magnesium (Mg2+). From the analysis results, it was observed that the column depth had a significant influence on the removal efficiency of the pollutants. The highest removal efficiency (94.58%) was achieved from the combination of electrical conductivity and 1 m column depth, while the lowest removal efficiency (10.05%) was observed from the combination of calcium and 0.5 m column depth. The raw wastewater fell mostly into a “very high” hazard, which is class four (C4) based on electrical conductivity and class four (S4) based sodium adsorption ratio; making it unsuitable for irrigation purposes. However, when the wastewater was subjected to 1 m column depth, the quality of the treated effluent improved significantly which in turn also improved the suitability of the effluent for irrigation purposes, with percent compliance ranging from 20.19% to 97.54%.

Wastewater Management in Nunavut: Public Health Concerns and Canadian Sanitation Inequities

Wastewater management is difficult and expensive at the best of times but is particularly challenging under harsh Arctic conditions. In Nunavut, wastewater is treated via waste stabilisation ponds because of their relatively low capital and operational costs, and minimal complexity. However, there are inefficiencies in the removal of pathogens relating to the extremely cold temperatures which limit the biological processes of wastewater treatment. As a result, serious public health risks are associated with the human exposure to untreated wastewater. This is particularly true for Indigenous populations that rely on traditional diets for sustenance. Engineering alone will not properly address the issue of wastewater management in Nunavut as Indigenous populations are chronically overlooked in Canadian public policy. Three aspects of Canadian legislation will be discussed in this paper that are imperative for the long-term fight for equality of water and sanitation.

Decentralized sanitation solutions for temporal Internally Displaced people (IDPs) and refugees camps and residential complexes in Duhok province – Case study

The conditions of the settlements are often very poor with deficiencies in basic supplies like water. This study aims to: (i) assess the sanitation service level for Internally Displaced People (IDPs) and refugee camps in Duhok province / Kurdistan of Iraq (ii) assess the performance of wastewater treatment plants (WWTPs) and offer different scenarios to improve the sanitation service level in the Duhok province (iii) propose various decentralized treatment approaches. To demonstrate the efficiency of WWTPs, samples of generated wastewater at the effluent of 12 residential projects were collected to conduct the COD test. The results of COD test were found to exceed the permissible level of 100 mg/L set by Iraqi wastewater standard except in New Zakho and Avro city projects. The highest generation rates of grey and black wastewater were in Chamishko and Kaberto1 IDP camps and were 1013 and 3000 m 3 /day respectively. Both Avro city and War city residential complexes were notably discharging the highest rates of wastewater at the effluent with 5610 and 2484 m 3 /day respectively. Lelav city, New Jin city, and Dabin projects were found to have the maximum organic loading rate of COD with 745, 578, and 332 kg/day respectively. This study proposed Waste Stabilization Pond (WSP) systems to be constructed in both Domiz1 refugee camp and Chameshko IDP camp. In order to be more achievable, it is suggested that the regulations of disposed wastewater at the effluent be amended and categorized on a class basis rather than using a single effluent number.

Effect of untreated or reclaimed wastewater drip-irrigation for lettuces and leeks on yield, soil and fecal indicators

Sanitary and environmental impacts, as well as effects on agricultural yields constitute important parameters to be taken into account in wastewater reuse projects, and depend on the treatment applied to the wastewater. Extensive treatments or irrigation with untreated wastewater are rarely studied, although they represent a significant share of unplanned or indirect wastewater reuse in the world. The aim of this study was to contribute to the evaluation of chemical properties of soil, crop yields, and the fate of fecal indicators in soil and plants when vegetable crops (lettuces and leeks) are irrigated by drip-irrigation using untreated wastewater (UW), water reuse or treated wastewater by stabilization ponds (TW) and fresh water (FW). Over two years (2018 and 2019), three lettuces ( Lactuca sativa ) and two leeks ( Allium porrum ) growth cycles were performed in a greenhouse, and soil analyses show increases in electrical conductivity (EC), chlorine (Cl), sodium (Na) and nitrate nitrogen concentrations (NO 3 ) when TW and UW irrigation methods were compared to FW. As a result, FW irrigation and conventional fertilization lead to lower lettuce yields compared to TW (between 43 to 85% lower yields depending on the cultivation period) ( p -value < 0.05). However, trends are not clear for UW. Leeks irrigated with FW have also a smaller fresh mass compared to TW and UW (around 35 % and 45 % differences in the median for UW and TW, respectively, p -value < 0.05), which shows a possible positive effect of continuous nutrient supply against the risks associated with higher water conductivity. In addition, in the soil, the irrigation with TW and with UW increases some concentrations, especially EC, mainly due to Cl and Na values. Fecal indicators increased from 1 to 2 log with the used of UW but the decay of fecal indicators in topsoils was slow (less than 1 log for enterococcus load after 6h), as shown by culture-based and molecular techniques (qPCR, droplet digital PCR). Fecal indicators were found in plants irrigated with untreated wastewater. • Untreated and treated wastewater irrigation reuse were evaluated for lettuce and leek crops. • Fresh water irrigation produced lower yields compared to treated wastewater. • Untreated wastewater irrigation may negatively affect some soil properties. • Die-off rate of fecal bacteria was slow in topsoils irrigated by untreated wastewater. • Contamination by fecal indicators of crop roots irrigated by untreated wastewater.

Characterization and evaluation of waste stabilization pond systems in Namibia

Abstract Waste stabilization ponds (WSP) exist worldwide to treat wastewater, especially in warm climates. They are characterized by simple operation and maintenance and over 50 years many WSP were built in urban communities in Namibia. This study characterized and evaluated nine of these WSP systems in terms of their influent and effluent water quality and compared them with the requirements for water reuse in agriculture. In their current state none of them adhered with the Namibian or the new European reuse standards, especially due to tCOD concentrations above 100 mg/L caused by high algal fractions in the pCOD. The algae related chlorophyll-a concentrations correlated linearly with the pCOD and this correlation can therefore be used to fractionate the tCOD for further judgement. Additionally, microbial community analyses determined the composition of pathogens in the WSP influent and effluent, this helped to assess potential risks and distinguish between potentially toxic and non-toxic cyanobacteria. The EU requirement of less than 1,000 E. coli per 100 mL for fodder crop irrigation was only achieved with one WSP system which was enhanced with additional pre- and post-treatment. This research delivers a first overview of the current situation and can be used as basis to establish possible enhancement measures for existing WSP as well as to investigate possible effluent application in agricultural irrigation.

Performance Evaluation of Wastewater Treatment Plants in El-Fayoum

The present study has been undertaken to evaluate performance efficiency of wastewater treatment plants (WWTPs) in El-Fayoum Markaz, El-Fayoum governorate in Egypt. The wastewater treatment plants using different treatment techniques were Active sludge, Oxidation ponds, Secondary - active sludge and Chemical (nanotechnology) which wastewater samples were collected from both influent and effluent of each plant. The key performance of each plant is estimated based on the treated wastewater quality data. Based on the results, they showed that Old Quhafa (Secondary - active sludge technology) operates with removal efficiencies higher than 80% for biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) were established. While Ezbet Ashour accomplished lowest performance efficiency that operates with chemical-nanotechnology. This analysis applied to define a performance measuring plan based on the most important parameters that can be reliable and applicable for any WWTP. The study suggested formula for performance WWTPs that described by the expressing removal efficiencies as relative values or percentages and the remaining fraction. The study recommended that sedimentation units must be cleaned, monitoring frequently of sludge analysis and calculation of building capacity for all WWTPs.

Evaluation of Waste Stabilization Pond Efficiency and Its Effluent Water Quality: a Case Study of Kito Furdisa Campus, Jimma University, Southwest Ethiopia.

Waste stabilization pond (WSP) technology is one of the most promising wastewater treatment methods. In developing countries, including Ethiopia, only a small proportion of the wastewater is being treated. Discharge of untreated wastewater into receiving water bodies may lead to disruption of ecological integrity, economic, and public health risks. However, there is limited evidence on WSP efficiency and effluent water quality in Ethiopia. A laboratory-based cross-sectional study was conducted on 60 wastewater samples. A standard method of procedure was used to collect and analyze samples. SPSS version-24 was used for statistical analysis and a paired t-test was used to test for statistical significant differences. A statistically significant difference (p < 0.001) in the removal efficiency of BOD5 up to 75.3% (117 mg/L effluent) and COD up to 56.5% (457.5 mg/L effluent) was recorded. A statistically significant difference (p < 0.001) in the removal efficiency of TN up to 79% (17.4 mg/L effluent), TP up to 69.2% (4.8 mg/L effluent), and PO4−3 up to 71% (3.36 mg/L effluent) was recorded. Whereas, a statistically significant difference (p < 0.001) in the removal efficiency of total coliforms up to 99.99% (3.4 × 103 MPN/100 mL effluent) and fecal coliforms up to 94.3% (8.54 × 102 MPN/100 mL effluent) was recorded. The overall efficiency of the treatment plant was 73.5% and its water quality index of the effluent water quality of WSP was 30. The finding showed that the efficiency of the WSP was judged as satisfactory and the effluent water quality of WSP is unsuitable for the discharge into the environment. Therefore, to improve the efficiency of the WSP and to produce adequately treated water, it required adequate preliminary treatment, modification of the design, desludging of the pond, additional treatment, and frequent monitoring and maintenance of the pond.

Evaluating the performance of conventional DAF and PosiDAF processes for cyanobacteria separation at a pilot plant scale

Abstract In this work, a commercially available water treatment polymer poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDADMAC) and a hydrophobically modified polymer (HMP) designed to adhere to bubble surfaces were applied for the first time in the novel Posi-dissolved air flotation process (PosiDAF) that uses polymer-modified bubbles, at pilot-scale for the treatment of waste stabilisation pond samples rich in algae. It was found that PDADMAC in PosiDAF gave comparable removal to that achieved using conventional DAF at &amp;gt;95% cell separation. Furthermore, the float layer was more uniform and thicker with up to 8% solid contents compared to conventional DAF, which comprised discrete floc clusters with an average solid concentration of ∼4.1%. In contrast to the use of PDADMAC, the application of the HMP did not achieve similarly good separation at pilot scale. It was hypothesised that this may be due to the micellisation of the HMP on the bubble surface, creating unstable bubbles that coalesced and prevented polymer–bubble–cell interactions, which are crucial for effective cell separation. On comparison of the costs of PosiDAF and conventional DAF, it was found that PosiDAF resulted in cost-savings of up to 74% due to low chemical consumption. In summary, PosiDAF reduced chemical cost and increased solid contents in the metal-free float.

Feasibility Analysis of the Utilization of Constructed Wetlands in Small High-Andean Urban Agglomerations

This article shows the results of bibliographic and documentary research and an in-situ visit to the treatment plants of small populations around the circunlacustrine ring of Lake Titicaca; with the aim of carrying out a feasibility analysis of the utilization and exploitation of artificial wetlands (wetlands) as an alternative for the domestic wastewater treatment of small urban agglomerations in high-Andean areas. From the visit to the thirteen localities and fourteen treatment plants, it was observed that in six of them, they just have stabilization ponds, and without maintenance, and eight have biological filter treatments and from these, just three have some maintenance, that is why the great majority is practically abandoned. In addition, they do not have an energy supply and they have sloping orographic conditions, as far as there is a great potential of eleven treatment plants, for the extensive technologies implementation (artificial wetlands), thereby reducing the discharge of wastewater without any treatment to the Lake Titicaca.

Industrial reuse of petrochemical effluents: A case study of ultrafiltration and reverse osmosis

The petrochemical industry uses high volumes of water in its production processes and generates effluents that have a great potential for reuse in production processes. The reuse of these effluents is, therefore, an alternative for the sustainable development of the sector. This study aimed at evaluating the application of ultrafiltration (UF) and reverse osmosis (RO) in the treatment of petrochemical effluents for the production of industrial reuse water, reducing environmental impacts caused by the disposal of effluents in the soil. The experiments were carried out with effluents named waste stabilization pond 1 (WSP-1), waste stabilization pond 8 (WSP-8) and an inorganic effluent (INO), which was used as feedwater in the pilot unit with a treatment capacity of 1 m³.h–1. The parameters chosen for evaluation in the treated effluents were calcium, magnesium, chloride, sulfate, electrical conductivity (EC), total organic carbon, color, chemical oxygen demand (COD), pH, total suspended solids and turbidity. Membrane permeate fluxes were determined to evaluate the performance of the pilot system. After treatment and characterization of each effluent, the results were compared to define the most suitable effluent to achieve the quality required for industrial reuse. The results showed that the proposed UF/RO treatment provided a stable flux for the WSP-8 effluent. Conversely, the other streams showed an accentuated decrease in flux, which indicates fouling processes of the UF and RO membranes. As for the efficiency of the treatment, the process removed compounds of interest such as COD above 90%, salts and EC above 92% for the three assessed effluents. Thus, considering all aspects evaluated in this study, WSP-8 was the most suitable to be used as feed in the pilot system with UF and RO. The permeate produced presented the necessary quality for reuse in the industries of the Southern Petrochemical Complex, presenting equivalent characteristics to those of clarified water. Thus, the reuse of treated petrochemical effluents may be an important alternative source of water resources in face of availability and scarcity restrictions in industries in southern Brazil.

Demonstration study of bypass stabilization pond system in the treatment of eutrophic water body.

This study involved a comprehensive renovation of fish ponds to improve the water quality of a eutrophic river in Dongguan City. The abandoned fish ponds were transformed into three different types of stabilization ponds: facultative, aerated biological, and submerged plant stabilization ponds. The water of the eutrophic section of the river was pumped into the facultative stabilization pond and discharged into the Haizai River through an aerated biological pond and a submerged plant pond. In the aerated biological pond, secondary treatment was carried out using plant zoning and artificial floating island aeration system. The submerged plant pond used fountain-type aeration and an underwater forest for tertiary treatment. After four months of monitoring the water quality of the stabilization pond and the river, the ammonia nitrogen (NH3-N), total phosphorus (TP), and chemical oxygen demand (CODCr) levels in the raw sewage reduced from 6.53 mg/L to 1.13 mg/L, 1.76 mg/L to 0.29 mg/L, and 63 mg/L to 22 mg/L, respectively; the transparency of water increased to 45 cm, and dissolved oxygen (DO) level increased to 5.32 mg/L. This study provides a reference for the ex-situ treatment of urban eutrophic waterbodies.