Management Of Wastewater Treatment Plants Research Articles

Dynamic simulation for wastewater treatment plants management: Case of Souk-Ahras region, north-eastern Algeria

AbstractTreatment performances of two wastewater treatment plants (WWTPs), located in North-Eastern Algeria (Souk-Ahras and Sedrata) were tested using ASM1 model. The model, to be considered as a decision tool for the appropriate management of activated sludge systems, served for the prediction of both WWTP behaviours under different operating conditions. In Sedrata WWTP the first management scenarios is based on an increase of inflow rate, taking into account a new transfer volume from a nearby zone. In a second scenerio, the ultimate flow of 40 000 m3·d-1 is estimated. Regarding Souk-Ahras WWTP, three scenarios were tested. The first tested the impact of an increase of the extraction flow rate and yielded a reduction by 37% of sludge production. The second dealt with the management of the mass budget of substrata and biomass. Finally, the third application was devoted to the estimation of the plant ultimate capacity, estimated to be 60 000 m3·d-1.

Sustainability study of domestic communal wastewater treatment plant in Surabaya City

Sanitation is one of the critical infrastructure sectors in order to improve community health status. The Ministry of Public Works of the Republic of Indonesia to define that word sanitation include: domestic waste water management, solid waste management, rain water management (drainage management) as well as the provision of clean water. Surabaya city as the capital of East Java province and Indonesia’s second largest city with a population of 2,853,661 inhabitants in 2014 (the second largest after Jakarta), but the people who have been served by the sanitation infrastructure systems were expected at 176,105 families or about 26.95 % of the population of the city is already using sanitation facilities. In the White Book Sanitation of Surabaya City in 2010, Surabaya City sanitation development mission is to realize the wastewater management of settlements in a sustainable and affordable by the community. This study aims to assess the sustainability of the wastewater treatment plant (WWTP) domestic communal in the city of Surabaya. The method in this research is quantitative method through observation, structured interviews and laboratory testing of the variables analyzed. Analyses were performed using a technique Multidisciplinary rapid appraisal (Rap-fish) to determine the level of sustainability of the management of communal WWTP based on a number of attributes that easy scored. Attributes of each dimension includes the technical, environmental quality, institutional, economic, and social. The results of this study are sustainability index of environmental quality dimension at 84.32 with highly sustainable status, technical dimension at 62.61 with fairly sustainable status, social dimension at 57.98 with fairly sustainable status, economic dimension at 43.24 with less sustainable status, and institutional dimension at 39.67 with less sustainable status.

Wet Oxidation of sewage sludge: a mathematical model for estimating the performance based on the VSS/TSS ratio

Wet Oxidation (WO) models are generally employed for reactor design, thus WO modeling is a topic of great interest. Indeed, WO is one of the different technologies studied for sludge minimization and treatment, which represent crucial aspects in the management of wastewater treatment plants (WWTP). Different Generalized Lumped Kinetic Models (GLKM) for sewage sludge WO were proposed in the literature for describing the complex transformations occurring in the process. Usually, works are related to a single type of sludge and, consequently, kinetic constants cannot be used for different case studies. In the present paper an alternative approach has been followed. A mathematical model was proposed and identified on a set of six different types of sludge (primary, secondary and mixed sludge from both urban and industrial WWTP). Kinetic parameters were determined for the different types of sludge with the non-linear least-squares method. In general, the predicted COD values obtained with the estimated kinetic constants closely fit experimental data: the mean absolute error associated with total (dissolved) COD is 3.2% (3.7%) and 10% (17%), respectively for the best and worst case. Kinetic constants values were finally correlated to the sludge VSS/TSS ratio (VSS=Volatile Suspended Solids; TSS=Total Suspended Solids) in order to provide a tool for a gross estimation of WO kinetic parameters, for a given sludge, relying on simple analytical measurement (VSS and TSS), commonly available at every WWTP.

Eco-efficiency assessment of wastewater treatment plants using a weighted Russell directional distance model

Improving the performance of wastewater treatment plants is essential to ensuring their long-term sustainability. Most of the previous studies on this topic have assessed the techno-economic efficiency of wastewater treatment plants and ignored the emission of greenhouse gases. For the first time, the weighted Russell directional distance model was applied to estimate the eco-efficiency of a sample of real wastewater treatment plants. Moreover, this approach allowed an inefficiency score to be obtained for each variable (cost factors, pollutant removal and greenhouse gases) involved in the model. Subsequently, a second stage of analysis was applied to identify factors influencing the previously computed inefficiency scores. The results illustrated that approximately half of the facilities assessed had significant room for improvement in their eco-efficiency. Moreover, the characteristics of over- and undersizing of the plants significantly affected their eco-efficiency. The methodology and results of this study are of great interest, not only for wastewater treatment plant managers and water authorities but also for citizens because there have been growing concerns regarding minimizing the ecological footprint in the urban water cycle.

A step forward in the management of multiple wastewater streams by using an ant colony optimization-based method with bounded pheromone

Wastewater treatment systems (WTSs) have as an objective to efficiently treat the wastewater flows that they receive. Wastewater treatment plants (WWTP) process optimization is generally based on biological process optimization, which is usually related to the quantity and quality of the WWTP inflows. The inflow contributions sometimes destabilize the biological system due to flow and nutrient load limitations, with a higher impact in small and decentralized systems. Their management is a complex task due to the multiple constituents and different flows, but it should be the first step for a general, optimal and comprehensive optimization.Ant colony optimization (ACO) has demonstrated the ability to solve these complex problems, as metaheuristic methodologies, using an iterative and probabilistic procedure. This work proposes to solve the treatment influent composition by using two ACO algorithms. Both algorithms apply bounded pheromone trails to resolve the failures in the search for an optimal solution limited by inflow constraints. The results present high efficacy in maximizing the total wastewater inflow that fulfils all the constraints and improving the WWTP management with different inflows and constraints.

Environmental impact assessment of centralized municipal wastewater management in Thailand

Urbanization and industrial development intensify water utilization and wastewater generation. The efficiency of wastewater treatment systems varies and depends on system design and wastewater condition. The research aims to examine seven existing centralized municipal wastewater treatment plants (WWTPs) in Bangkok to discover which system configuration yields the best environmental and economic performance. The degree of environmental impact and operational costs from different system designs were investigated to help select future wastewater treatment systems. Life cycle assessment (LCA) has been conducted to evaluate environmental impacts from centralized municipal wastewater treatment systems. Life cycle impact assessment method based on endpoint modeling (LIME) was applied, with three major potential environmental impact categories including eutrophication, global warming, and acidification. All seven centralized municipal WWTPs in Bangkok were investigated as case studies. The system configurations are classified into five types of activated sludge (AS) systems. The contribution of impacts from individual processes in each type of AS system was analyzed. The methodology covered major on-site and off-site operational processes excluding construction and maintenance phases. Average annual data were calculated to develop an inventory dataset. JEMAI-Pro software was utilized in this study to analyze the life cycle impact of the systems. The level of environmental impact from a WWTP depends on the configuration of the AS system. The highest potential environmental impact from a municipal WWTP is eutrophication, which is obviously affected by ammonium and phosphorous discharges into water bodies. The vertical loop reactor activated sludge (VLRAS) system yielded the best treatment performance among the five AS sub-systems. The consumption of electricity used to operate the system contributed significantly to global warming potential and correlated considerably with operating costs. Comparing among three system sizes, the large-scale WWTP revealed inefficient electricity consumption, whereas the medium plant provided better performance in chemical use and operating costs. Centralized municipal WWTPs with capacities ranging from 10 to 350 × 103 m3/day were evaluated with respect to environmental performance and costs during the operating phase. Among all case studies, a medium-scale WWTP with a VLRAS system offered the best operating performance in terms of low environmental impact, resource consumption, and cost. To enhance WWTP management, it is vital to improve the efficiency of electricity consumption in primary and secondary treatment processes and increase wastewater collection efficiency to maximize the plant operating capacity and minimize overall environmental impacts.

Evaluation of Groundwater Resources for Drinking and Domestic Purposes in Related to Human Activities at Assiut Area- Egypt

Generally, the arid zones are characterized by scare or limitation in their water resources. During the last few years, these water resources suffered from agricultural, human and urbanization pollutants. So a plan for water quality assessment is needed. The present study aims to evaluate groundwater resources for drinking and domestic purposes. To achieve this goal, 109 groundwater samples was collected from groundwater resources in Assiut Governorate at autumn season 2013. Chemical analysis of the major and some trace elements were care out at Geology Department - Faculty of Science - Minia University and Environmental Affairs Agency. World Health Organization and Egyptian Stander guideline taken into consideration in evaluating the water for human drinking and domestic uses. The resulted data of chemical analysis of major and trace elements showed that; About 96.3% of groundwater samples are ranging between acceptable and permissible for human drinking and only 3.7% of groundwater samples are unsuitable due to their high content of total dissolved solids (TDS). But Most of groundwater samples (91.74%) are unacceptable for human drinking because it's higher content of some minor and trace elements as Manganese (Mn), Cadmium (Cd) and Chromium (Cr) and the remain samples are acceptable. According to (WHO, 2004) and Eg. St., (1995, 2007) guidelines for drinking water quality, [Total dissolved Soled (TDS), major ions, minor and trace, etc constituents]- total evaluation; about 96.3% of groundwater samples incompatible and the rest samples are compatible when compared with (WHO, 2004). While 8.26% compatible and 91.74% of groundwater samples are incompatible when compared with (Eg. St. 1995, (2007). All groundwater samples 100 % are very hard for domestic and laundry. According to the guideline National Academy of science (NAS) and National Academy of Engineering (NAE), (1972) and (Mckee, 1963), most groundwater samples (96.3 %) are excellent for livestock and poultry. The rest 3.7 % are very satisfactory. The present study recommends management of pollution sources, including an application of Agrochemicals and controlling the seepage of wastewater from rural as well as management of wastewater treatment plants, protecting the area around the pumping well and the outlet of drinking water treatment plants, Continuous monitoring of water resource using for drinking purposes.

Development of an operational performance indicator system for activated sludge wastewater treatment plants

Sustainable operation, optimisation and performance evaluation of municipal wastewater treatment plants (WwTPs) in Ireland is topical due to the transfer of water and wastewater operational and capital delivery functions from 34 local authorities to a single national water utility in Ireland. This paper describes the development process of a sustainable optimisation indicator (SOI) system for small-to-medium sized activated sludge (AS) WwTPs using a stakeholder-based approach. The SOI system provides a framework of indicators for performance assessment to facilitate continuous sustainable performance improvement of AS WwTP operations. The findings from plant optimisation and stakeholder consultation studies and the mechanism for their contribution to the development of the SOI system indicators and framework are presented. The proposed system is applicable to wide range of stakeholders for the sustainable and improved monitoring, operation and management of AS WwTPs.

Life cycle assessment and economic efficiency analysis of integrated management of wastewater treatment plants

This paper evaluates several Wastewater treatment plant (WWTP) processes, an integrated sludge management system, and waste sludge disposal methods in a large city based on life cycle analysis (LCA) and economic efficiency analysis (EEA) together. Among the three WWTP processes considered, the A2O process (S-WWTP) showed the lowest eutrophication potential (EP) and global warming potential (GWP), but the highest acidification potential (AP) and human toxicity potential (HTP). Simple integration of sludge treatment by combining two sludge treatment lines resulted in enhanced anaerobic digestion and production of less sludge. For final sludge disposal, incineration with integrated sludge management showed the highest reduction of life cycle impact analysis (LCIA) in all four categories. The simple integration of sludge management could reduce the sludge handling cost by 6.1%. As a final sludge disposal method, incineration with integration of sludge management was the most economic: reducing operation and management (O&M) cost by 33%. These results demonstrated that application of LCA and EEA would be a useful tool for optimizing an integrated sludge-management system. The proposed integrated sludge-management alternatives could provide a valuable example for managing several WWTPs in a large city.

Towards A New Decision Support System for Design, Management and Operation of Wastewater Treatment Plants for the Reduction of Greenhouse Gases Emission

The increasing attention paid to the environment has led to a reduction in the emissions from wastewater treatment plants (WWTPs). Moreover, the increasing interest in the greenhouse gas (GHG) emissions from WWTPs suggests that we reconsider the traditional tools used for designing and managing WWTPs. Indeed, nitrous oxide, carbon dioxide and methane can be emitted from wastewater treatment, significantly contributing to the greenhouse gas (GHG) footprint. The reduction of energy consumption as well as GHG emission are of particular concern for large WWTPs which treat the majority of wastewater in terms of both volume and pollution load. Nowadays, there is an increasing need to develop new tools that include additional performance indicators related to GHG emissions and energy consumption as well as traditional effluent quality parameters. Energy consumption, in fact, can be considered as an indirect source of GHGs. This paper presents the development of an ongoing research project aiming at setting-up an innovative mathematical model platform for the design and management of WWTPs. The final goal of the project by means of this platform is to minimize the environmental impact of WWTPs through their optimization in terms of energy consumptions and emissions, which can be regarded as discharged pollutants, sludge and GHGs.

Performance evaluation of the main units of a refinery wastewater treatment plant – A case study

Petroleum refineries generate great amounts of wastewaters which require proper treatment before being discharged into coastal waters or other aquatic systems. The main pollutants present in these industrial wastewaters include suspended particles, biodegradable and refractory organics, hydrocarbons, sulfides, phenols and nitrogen compounds. The performance of the Porto Refinery wastewater treatment plant (WWTP) was evaluated in this study. Five sampling campaigns were carried out at six sampling points of the (WWTP), with the purpose of analyzing the most relevant physicochemical parameters and determining the removal efficiencies in each treatment step and the WWTP overall efficiency. The obtained results show that the Porto Refinery WWTP operates with removal efficiencies higher than 90% for TSS, VSS, TPH, O&G, sulfides and phenols, between 80 and 90% for COD, BOD5 and total nitrogen and around 60% for chlorides. The final effluent meets the discharge limits imposed by the Portuguese legislation. A correlation analysis between the most relevant parameters under study was performed, which contributes to define a reliable monitoring plan based on a limited number of parameters, and provides valuable information regarding the process efficiency, at low cost, to the WWTP managers.

Chemical speciation of heavy metals in excess sludge treatment by thermal hydrolysis and anaerobic digestion process

Adequate treatment of excess sludge from municipal wastewater treatment plants (WWTP) is a critical issue nowadays in WWTP management. Thermal hydrolysis and anaerobic digestion are the methods often used to reduce the organic content of the excess sludge. However, these two methods have very limited effects on heavy metals’ removal. As the toxicity of heavy metals is closely related to not only their quantity but also in their chemical speciations, more in-depth studies on heavy metals speciation distribution are needed. In this paper, the speciation of eight kinds of heavy metals before and after thermal hydrolysis and anaerobic digestion were investigated using a modified BCR (Bureau Communautaire de Référence: a four-step sequential extraction process proposed by the European Community Bureau of Reference in 1992) sequential extraction process. The results showed that the stable content of eight kinds of heavy metals increased by various extents after thermal hydrolysis. The chemical speciation of heavy metals during thermal hydrolysis and anaerobic digestion exhibited significant changes from non-stable to relatively stable state. The existence of H2S can reduce the activity of anammox bacteria, and thus can lead to the deterioration of anaerobic biological treatment system. However, the toxicity of H2S and heavy metal ions can be significantly inhibited simultaneously by the interaction between heavy metals and H2S without secondary pollution, which is beneficial for excess sludge disposal.

Implementing a respirometry-based model into BioWin software to simulate wastewater treatment plant operations

The management of wastewater treatment plants to comply with new strict effluent criteria is a great concern: the activated sludge modeling, when supported by an accurate calibration process, could be an essential tool for this purpose. In the present paper, three WWTPs were characterized in order to support their up-grade. Influent characteristics and activated sludge performances were studied by application of respirometry. Plant operations were simulated by BioWin software (EnviroSim Associates Ltd., Canada). The goodness of the simulation, checked by the calculation of the average relative deviation between measured and simulated data, demonstrated that the model was able to predict the plant performances.

차집관로와 하수처리시설의 설치에 따른 도시하천의 수질변화 특성

Abstract : In this study, the characteristics of water quality change of the three streams in Daejeon were analyzed according to the expanded installation of interceptors and wastewater treatment plant (WTP). Gabcheon 5 (Singu Bridge) location showed the maximum difference of the highest and lowest concentrations in the last decade. However, the recent water quality of this location was worse than other locations, because of the impact of the effluent from the WTP. In the upstream of the WTP, the Daejeon stream was relatively better than the other locations in organic pollution reduction, and this was caused by the investment for the management of the interceptors in three streams of Daejeon. According to the water quality standard of the stream water quality, the recent water quality of the three streams in Daejeon was acceptable within them in the most of the water quality items, but because the total phosphorus concentration of the upstream such as Daejeon stream, Yudeng stream, Gabchen 3 location did not reach the standard values, a better management of the interceptor was required in the upstream of WTP than its downstream. The upstream of WTP also required a better management of the interceptor than the downstream. The operation and management of WTP was required a high efficiency because the water quality of the effluent from the WTP incurred an adverse effect to the target water quality in the location of the total water pollution load management system.

Selection of an appropriate risk assessment tool for waste water risk abatement planning: an eThekwini case study

A Wastewater Risk Abatement Plan (WWRAP) has become an integral part in the operation of wastewater treatment plants across South Africa with the introduction of the Green Drop initiative. With each successive Green Drop season the WWRAP has become more of a focal point of the assessments and is intended to engender a more risk aware and risk averse philosophy into the operation of wastewater plants. The WWRAP, itself, is intended to be used as a tool to prioritize the deployment of limited resources and funds to achieve better compliance and management of wastewater treatment plants across the country. This is only effective if the method used for rating risk successfully identifies risks inherent on the plants. In essence the WWRAP will not achieve its objectives unless risks are properly identified. This paper explores the two successive WWRAPs produced by the eThekwini Municipality and the evolution of the risk rating systems employed. In 2011 the eThekwini Municipality's WWRAP was based on a modified risk matrix as proposed in the Draft Guidelines for the development of WWRAPs by DWA and the WRC. While the results of this assessment generally correlated with the Department of Water Affairs' Cumulative Risk Rating assessments, the rating system was based primarily on health targets and as a result was ineffectual as a tool for prioritization of resources. In 2012 with the next revision of the WWRAP there was a need to further ‘tweak’ the risk matrix used in order to more accurately reflect and identify risks on the various plants. This entailed increasing the complexity of the risk rating methodology and care was taken to ensure usability while still enhancing the efficacy of the risk assessment process. It was decided that ‘Administrative’ or ‘Reputational’ risk be taken into account when evaluating risk at the various plants and the risk assessment matrix was adjusted accordingly. It was decided that both administrative and reputational risk could be adequately represented by the influence that a particular risk had on the Affairs' potential Green Drop score. Multiple permutations and approaches were evaluated to determine which method would best reflect the ‘on the ground situation’. Using the new rating system, a total of 1,235 low risks were identified over the previous year's 913, medium risks numbered 223 over the 17 from 2011 and 105 high risks were identified for 2012 as compared to 2011 where no high risks were identified at all. The new rating system was thus deemed a more appropriate tool for the prioritization of resources for the municipality.

How can sludge dewatering devices be assessed? Development of a new DSS and its application to real case studies

A key issue in biological Waste Water Treatment Plants (WWTPs) operation is represented by the sludge management. Mechanical dewatering is a crucial stage for sludge volume reduction; though, being a costly operation, its optimization is required. We developed an original experimental methodology to evaluate the technical (dewatering efficiency) and financial (total treatment costs) performance of dewatering devices, which might be used as a DSS (Decision Support System) for WWTP managers. This tool was then applied to two real case studies for comparing, respectively, three industrial size centrifuges, and two different operation modes of the same machine (fixed installation vs. outsourcing service). In both the cases, the best option was identified, based jointly on economic and (site-specific) technical evaluations.

Inhibition of the nitrification process in activated sludge by trivalent and hexavalent chromium, and partitioning of hexavalent chromium between sludge compartments

The input of wastewater treatment plants (WWTPs) may contain high concentrations of Cr(III) and Cr(VI), which can affect nitrogen removal. In the present study the influence of different Cr(III) and Cr(VI) concentrations towards activated sludge nitrification was studied. To better understand the mechanisms of Cr(VI) toxicity, its reduction, adsorption and uptake in activated sludge was investigated in a batch growth system. Quantification of Cr(VI) was performed by speciated isotope dilution inductively coupled plasma mass spectrometry. It was found that Cr(VI) concentrations above 1.0mgL−1 and Cr(III) concentrations higher than 50mgL−1 negatively affected nitrification. Speciation studies indicated almost complete reduction of Cr(VI) after 24h of incubation when Cr(VI) concentrations were lower than 2.5mgL−1, whereas for Cr(VI) added to 5mgL−1 around 40% remained unreduced. The study of the partitioning of Cr in the activated sludge was performed by the addition of Cr(VI) in concentrations of 2.5 and 5.0mgL−1. Results revealed that Cr was allocated mainly within the intercellular compartments, whereas intracellular and adsorbed Cr represented less than 0.1% of the Cr sludge concentrations. Cr(VI) was reduced in all compartments, the most efficiently (about 94%) within the intracellular and intercellular fractions. The extent of reduction of adsorbed Cr was 92% and 80% for 2.5 and 5.0mg of Cr(VI) L−1, respectively. The results of present investigation provide a new insight into the toxicity of Cr species towards activated sludge nitrification, which is of significant importance for the management of WWTPs in order to prevent them from inflows containing harmful Cr(VI) concentrations.

The Use of Simulation Modelling for Optimisation of Phosphorus Removal in Sewage Treatment under Varying Influent Loading

A validated ASM2 model (STOAT) for the Changzhou WWTP was used to evaluate operational problems encountered in most wastewater treatment plants, during the transitional period from winter to summer. Favourable operating conditions which can achieve both TN and TP effluent concentrations under varying influent loading without the use of either chemical polishing or external carbon sources were established. Further, the use of 1.5 h wastage pump run time and 4.5 h cycle time was found better than the 3 h wastage pump run time and the 6 h cycle time as practiced in most WWTPs, as the latter is sufficient to allow second TP release, whereas the former is found to improve effluent TP by approximately 73%. The model was applied to troubleshoot another WWTP successfully. The finding in this study will improve the management of wastewater treatment plants for better and consistent effluent quality at a reduced capital cost.

A comprehensive method for the evaluation of biological nutrient removal potential of wastewater treatment plants

An evaluation method based on the supply and demand of carbon source in the biological nutrient removal (BNR) process, combined with an index of difficulty of nutrient removal (DNR), was put forward to achieve comprehensive assessment and analysis of the BNR potential of wastewater treatment plants (WWTPs). Twenty-five full-scale municipal WWTPs with different BNR processes were evaluated over a period of 12 months in Shanghai (China). Statistical analysis results showed that the DNR index had significant positive correlation (r > 0.790, p < 0.01) with total nitrogen, total phosphorus concentrations in the effluent, and yielded higher correlation coefficient with BNR efficiency than the C/N and C/P ratios that were conventionally used to estimate carbon source supply conditions. According to the WWTPs ranking by DNR evaluation, the number of WWTPs with low, medium, high, and extremely high DNR level was 8, 10, 6, and 1 among the 25 WWTPs, respectively. The developed method can evaluate and analyze the BNR potential scientifically and objectively, and the ranking results can be used to guide level-to-level management, upgrading, and optimization of WWTPs under different discharge standards.

Monitoring Urban Wastewaters’ Characteristics by Visible and Short Wave Near-Infrared Spectroscopy

On-line monitoring of wastewater parameters is a major scientific and technical challenge because of the great variability of wastewater characteristics and the extreme physical-chemical conditions that endure the sensors. Wastewater treatment plant managers require fast and reliable information about the input sewage and the operation of the different treatment stages. There is a great need for the development of sensors for the continuous monitoring of wastewater parameters. In this sense, several optical systems have been evaluated. This article presents an experimental laboratory-based approach to quantify commonly employed urban wastewater parameters, namely biochemical oxygen demand in five days (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), and the ratio BOD5:COD, with a visible and short wave near infrared (V/SW-NIR) spectrometer (400–1000 nm). Partial least square regression (PLSR) models were developed in order to quantify the wastewater parameters with the recorded spectra. PLSR models were developed for the full spectral range and also for the visible and near infrared spectral ranges separately. Good PLSR models were obtained with the visible spectral range for BOD5 (RER = 9.64), COD (RER = 10.88), and with the full spectral range for the TSS (RER = 9.67). The results of this study show that V/SW-NIR spectroscopy is a suitable technique for on-line monitoring of wastewater parameters.