Large Wastewater Treatment Plant Research Articles

Fueling of a marine-terrestrial ecosystem by a major seabird colony

Seabirds redistribute nutrients between different ecosystem compartments and over vast geographical areas. This nutrient transfer may impact both local ecosystems on seabird breeding islands and regional biogeochemical cycling, but these processes are seldom considered in local conservation plans or biogeochemical models. The island of Stora Karlsö in the Baltic Sea hosts the largest concentration of piscivorous seabirds in the region, and also hosts a large colony of insectivorous House martins Delichon urbicum adjacent to the breeding seabirds. We show that a previously reported unusually high insectivore abundance was explained by large amounts of chironomids—highly enriched in δ15N—that feed on seabird residues as larvae along rocky shores to eventually emerge as flying adults. Benthic ammonium and phosphate fluxes were up to 163% and 153% higher close to the colony (1,300 m distance) than further away (2,700 m) and the estimated nutrient release from the seabirds at were in the same order of magnitude as the loads from the largest waste-water treatment plants in the region. The trophic cascade impacting insectivorous passerines and the substantial redistribution of nutrients suggest that seabird nutrient transfer should be increasingly considered in local conservation plans and regional nutrient cycling models.

Technological characteristics of reject waters from aerobic sludge stabilization in small and medium-sized wastewater treatment plants with biological nutrient removal

Most studies on the impact of reject waters recycled from sludge processing in the multi-phase activated sludge process focus on anaerobic sludge treatment in large wastewater treatment plants, leaving apart the processes of aerobic sludge stabilization often used in smaller facilities in rural and suburban areas. The article presents the results of tests carried out in three small and medium-sized wastewater treatment plants with biological removal of biogenic compounds that use aerobic stabilization to process sludge. The research concerned the quantity and quality of reject waters generated in the process of aerobic stabilization and dewatering of sewage sludge and their impact on the multi-phase activated sludge process. The results showed that the average volume of generated reject waters ranged from 3.2 to 5% of the incoming wastewater volume. The average share of organic compounds and total nitrogen loads contained in reject waters did not usually exceed 5–10% of the loads in raw wastewater but reached almost 50% in the case of total phosphorus. Studies indicated that the composition of the supernatant from aerobic stabilization is strongly dependent on the course of the process. The best quality was obtained for cyclic operation of the aerobic stabilization tank with 16 h of aeration and 8 h of settling. The results also showed the negative impact of sudden discharges of reject waters from sludge processing to a multi-phase biological reactor, which can be reduced by using an appropriate equalization tank and pretreatment of the side stream to reduce the recirculation of phosphorus.

Screening for 32 per- and polyfluoroalkyl substances (PFAS) including GenX in sludges from 43 WWTPs located in the Czech Republic - Evaluation of potential accumulation in vegetables after application of biosolids

Highly persistent, toxic and bioaccumulative per - and polyfluoroalkyl substances (PFAS) represents a serious problem for the environment and their concentrations and fate remain largely unknown. The present study consists of a PFAS screening in sludges originating from 43 wastewater treatment plants (WWTPs) in the Czech Republic. To analyze an extended group of PFAS consisting of 32 PFAS, including GenX and other new replacements of older and restricted PFAS in sludge, a new method was optimized and validated using pressurized solvent extraction, followed by the SPE clean-up step to eliminate the observed matrix effects and LC-MS/MS. The results revealed high PFAS contamination of sewage sludge, reaching values from 5.6 to 963.2 ng g−1. The results showed that in the majority of the samples (about 60%), PFOS was the most abundant among the targeted PFAS, reaching 932.9 ng g−1. Approximately 20% of the analyzed samples contained more short-chain PFAS, suggesting the replacement of long-chain PFAS (especially restricted PFOA and PFOS). GenX was detected in 9 samples, confirming the trend in the use of new PFAS. The results revealed that significantly higher contamination was detected in the samples from large WWTPs (population equivalent > 50,000; p-value <0.05). Concerning the application of sludge in agriculture, our prediction using the respective PFAS bioconcentration factors, the observed concentrations, and the legislatively permitted management of biosolids in Czech Republic agriculture revealed that PFAS can cause serious contamination of cereals and vegetables (oat, celery shoots and lettuce leaves), as well as general secondary contamination of the environment.

Impact of differences in speciation of organic compounds in wastewater from large WWTPs on technological parameters, economic efficiency and modelling of chemically assisted primary sedimentation process

The aim of the study was to supplement the information missing in the literature on the influence of organic compounds speciation (percentage of chemical oxygen demand (COD) fractions, readily biodegradable and non–biodegradable dissolved organic matter; slowly biodegradable and non‒biodegradable insoluble organic matter) in wastewater on chemically assisted primary sedimentation process and its potential impact on the energy and economic balance of the plant. The statistical modelling of the chemically assisted primary sedimentation process using artificial neural networks (ANN) was a novelty. It was also important to check the differences resulting from the use of coagulants, polyelectolites and their doses. For both large wastewater treatment plants (>500,000 people equivalent) located in the various regions of the country in Central Europe only ferric chloride had a positive balance. The addition of polyelectrolyte in the Wroclaw wastewater did not affect the chemically assisted primary sedimentation process but in the Bialystok wastewater it strengthened the process effect. In both plants only doses from 10 to 40 mgFe/dm3 are cost-effective. The results indicate that the addition of polyelectrolyte should be taken into account in this application and was correlated with the amount of colloidal COD fractions in wastewater. The developed ANN models reflected well the effectiveness of COD removal in both large WWTP while the sensitivity analysis of individual ANN models showed differences in the variables affecting the calculation process of both models, despite similar values of parameters characterizing wastewater in both wastewater treatment plants.

Linking Hydrobiogeochemical Processes and Management Techniques to Close Nutrient Loops in an Arid River

In this study, we explore opportunities to optimize food-energy-water (FEW) resources by closing nutrient loops in arid-land rivers. Specifically, we evaluate source and sink behavior of nitrogen as nitrate (NO3-N) in three characteristic channels in the Middle Rio Grande Basin (Delivery and Drain channels associated with agriculture and the main channel of the Rio Grande). All three channels are located downstream of a large wastewater treatment plant that is the main contributor of nutrients to this reach of the Rio Grande. We used a mass balance approach paired with stable isotope analysis to determine sources and processing of NO3-N within the channels over time (a year) and through space (along ~15 to 50 km reaches). Results indicated the growing season was an important period of sink behavior for the Delivery channel and the Rio Grande, but the Drain channel was a year-round source. Stable isotope analysis of 15N and 18O found a distinct nitrate signature in the Drain associated with biological processing, as well as Rio Grande sites impacted by agricultural outflow, but no equivalent signature was present in the Delivery channel. Based on our findings, we provide recommendations to help close nutrient loops in the study system and analogous aridland irrigation networks by 1) minimizing loss during the transfer of nutrients from wastewater facilities to agricultural areas, and 2) minimizing enrichment to downstream aquatic ecosystems by sequestering nutrients that escape the nutrient loop.

Upgrading a large and centralised municipal wastewater treatment plant with sequencing batch reactor technology for integrated nutrient removal and phosphorus recovery: Environmental and economic life cycle performance

Although nutrient removal and recovery from municipal wastewater are desirable to protect phosphorus resource and water-bodies from eutrophication, it is unclear how much environmental and economic benefits and burdens it might cause. This study evaluated the environmental and economic life cycle performance of three different upgraded Processes A, B and C with commercially available technologies for nutrient removal and phosphorus recovery based on an existing Malaysian wastewater treatment plant with a sequencing batch reactor technology and diluted municipal wastewater. It is found that the integration of nutrient removal, phosphorus recovery and electricity generation in all upgraded processes reduced eutrophication potential by 62–76%, and global warming potential by 7–22%, which, however, were gained at the cost of increases in human toxicity, acidification, abiotic depletion (fossil fuel) and freshwater ecotoxicity potentials by an average of 23%. New technologies for nutrient removal and phosphorus recovery are thus needed to achieve holistic rather than some environmental benefits at the expense of others. In addition, the study on two different functional units (FU), i.e. per m3 treated wastewater and per kg struvite recovered, shows that FU affected environmental assessment results, but the upgraded Process C had the least overall environmental burden with either of FUs, suggesting the necessity to use different functional units when comparing and selecting different technologies with two functions such as wastewater treatment and struvite production to confirm the best process configuration. The total life cycle costs of Processes A, B and C were 10.7%, 29.8% and 28.1%, respectively, higher than the existing process due to increased capital and operating costs. Therefore, a trade-off between environmental benefits and cost has to be balanced for technology selection or new integrated technologies have to be developed to achieve environmentally sustainable wastewater treatment economically.

Optimization of recovery and utilization pathway of chemical energy from wastewater pollutants by a net-zero energy wastewater treatment model

Recovering chemical energy from wastewater is an important route to reduce the electricity input in wastewater treatment plants (WWTPs), which can significantly decrease the carbon footprint of wastewater treatment. Existing evaluation models of energy self-sufficiency focused on macroscopic substance-energy flow and considered the overall energy balance of WWTPs but ignored the substance and energy conversion process via microbial metabolism. In this study, a net-zero energy (NZE) model was established based on microbial metabolism and energy balance to estimate the potential for chemical-energy recovery from wastewater pollutants and the optimization of metabolic substrate allocation, which was implemented in a large WWTP with anaerobic digestion. The results indicate that temperature and ΔCOD were key influence factors for specific energy consumption μ. The average energy self-sufficiency rate was 43.9% under the existing operations in the WWTP. The energy self-sufficiency rates with optimized substrate allocation ranged from 58.3% to 110.6%, with an average value of 78.8%. The energy self-sufficiency rates obtained in July and August were higher than 100%, indicating that the WWTP could achieve NZE status and output electric energy in July and August, but not in other months. Seasonal variation significantly affected the potential of chemical energy recovery from wastewater pollutants in the WWTP. The average reduction in greenhouse gas emissions with energy recovery under optimal operation conditions reached 76.4% in the WWTP studied herein. The enhanced anaerobic digestion efficiency and optimization of substrate allocation between catabolism and anabolism could increase the possibility of achieving NZE status based on the model.

Temporal-spatial variation and environmental risk assessment of pharmaceuticals in tributaries of the Han River watershed, South Korea

Eight compounds from three categories of pharmaceuticals [5 antibiotics, 2 non-steroidal anti-inflammatory drugs, and 1 anti-epileptics] were monitored at 24 sites in the tributaries of the Han River watershed in South Korea, 2016. The seasonal occurrence, temporal-spatial variation, potential compound source(s), and a risk assessment of this watershed, which is the largest drinking water source in the country, were investigated. Clarithromycin was detected most frequently (72.2%) with the greatest median concentration (0.151 ± 0.072 μg L−1), followed by carbamazepine and sulfamethoxazole. The seasonality of the pharmaceuticals was observed, with higher concentrations and detection frequencies in spring than in summer and autumn; this was possibly caused by lower levels of microbial activities associated with lower water temperatures than other seasons. In terms of geographical variation, urban areas had higher pharmaceutical concentrations than rural areas, which was attributed to the former's high population density and largest wastewater treatment plants (WWTPs) regardless of season. The total concentration and detection frequency of WWTPs were 12.4 and 2.5 times higher in downstream sites than upstream sites, thereby conveying that WWTPs were the main source for the presence of pharmaceuticals in tributaries. According to the results produced from calculations of the risk quotient (RQ) of aquatic organisms, clarithromycin and sulfamethazine were identified as posing relatively high ecological risk (RQ > 1) during the spring that was identified for this study. This study can provide policymakers with scientific support for prioritizing pollutant management and collections of global data on emerging pollutants.

The impact of WWTP size and sampling season on the prevalence of antibiotic resistance genes in wastewater and the river system

There is a growing concern about the fate of antibiotic resistance genes (ARGs) during wastewater treatment and their potential impacts on the receiving water bodies. We hypothesised that the quantity of ARGs in effluents may be related to the size of wastewater treatment plants (WWTPs) and sampling season. To date, only several attempts have been made to investigate the impact of the above factors at the catchment scale. Therefore, the goal of the present study was to explore possible differences in the quantity of ARGs in treated wastewater from small, medium-sized and large WWTPs in the catchment of the Pilica River (9258 km2). The impact of treated wastewater on the concentration of ARGs was also determined along the river continuum from upland to lowland segments to the point of confluence with the Vistula (342 km).Treated effluent was sampled in 17 WWTPs, and river water was sampled in 7 sampling sites in four seasons. The concentrations of blaTEM, tet(A), ermF, sul1 and aac(6′)-Ib-cr genes, the integrase gene intI1 and the 16S rRNA gene were analysed by quantitative PCR. The physical and chemical parameters and nutrient concentrations (23 various parameters) in the analysed samples were determined. The highest absolute concentrations of the studied genes were noted in effluent samples from small WWTPs (p < 0.01). The concentration of ARGs (gene copies/mL) peaked in winter and spring samples (p < 0.04). The results of statistical analyses indicate that in small WWTPs, the absolute concentration of ARGs can be predicted based on the biochemical oxygen demand, in routine water analyses. However, none of the studied parameters supported predictions of ARG abundance in medium-sized and large WWTPs or in river water.

Energetic and environmental analysis of a wastewater treatment plant through static and dynamic monitoring activities

The article describes the results achieved in 5 years of monitoring of a large wastewater treatment plant (700,000 PE) in Southern Italy, which has a conventional activated sludge process scheme and electricity as exclusive energy source. The monitoring involved a preliminary phase ("static" monitoring) for the analysis of historical data on the main process-related variables, using the approach of normalization techniques. In the second monitoring phase ("dynamic" monitoring) the theoretical distribution of the energy load among the electromechanical units of the plant was first studied; then, an energy monitoring system was implemented on the most energy-consuming unit of the plant, a 500 kW turbo-blower, with the aim of analysing in detail its real-time performance and investigating potential correlations with other process parameters (wastewater flow rates and associated pollutant load). Results of the static monitoring suggest good overall performances, both from an energy and environmental point of view, even if the plant works close to the maximum hydraulic capacity due to the massive infiltrations. In particular, focusing on the energy performances, the plant consumes on average 0.17 kWh/m3, 28 kWh/PE/year and 0.66 kWh/kgCODremoved. The results of dynamic monitoring, on the other hand, indicate that the turbo-blower consumes 30% less energy than what initially estimated through the theoretical model, but its functioning does not seem to be influenced by the other process parameters; this latter result reveals an inadequate energy management of the most power-absorbing electromechanical units of the plant and the consequent need to adopt effective strategies for energy optimization.

Bioreactor Simulation with Quadratic Neural Network Model Approximations and Cost Optimization with Markov Decision Process

The efficient operation of activated sludge type wastewater treatment plants is an ongoing topic for the utility providers, where electric energy consumption shares are high, giving cca. 30 % of total operational costs. Intervention methods for intensification include fine tuning of aeration settings, sludge removal and the adjustment of recirculation rates. In order to analyze the effects of various process control strategies, activated sludge models (ASM) are used for the purpose of biokinetic modeling. In practice, most model simulators do not incorporate optimization and necessary auto-calibration of the latter, due to high computational demand of timeseries evaluation. In this paper, a new mathematical model is presented, which makes biokinetic simulations suitable for the use in decision support systems. Namely, the ASM model is approximated with a computanional inexpesive quadratic model solution, fed into a set of mass-balance corrected neural networks. Cost optimization is achieved with Markov decision process model. The developed method was illustrated for a case of Hungarian, large wastewater treatment plant. It was proven, the model is able to find better aeration schemes for the plant in aspect of cost of operation and nitrogen removal efficiency. The model can be used to find cost-optimal policies under arbitrary defined conditions. As a benefit, results can be implemented into industrial logic controllers.

Polyhydroxyalkanoates (PHAs) Production: A Feasible Economic Option for the Treatment of Sewage Sludge in Municipal Wastewater Treatment Plants?

Sludge is a by-product of municipal wastewater treatment plants (WWTPs) and its management contributes significantly to the operating costs. Large WWTPs usually have anaerobic sludge digesters to valorize sludge as methane and to reduce its mass. However, the low methane market price opens the possibility for generating other high value-added products from the organic matter in sludge, such as polyhydroxyalkanoates (PHAs). In this work, the economic feasibility of retrofitting two types of WWTPs to convert them into biofactories of crude PHAs was studied. Two cases were analyzed: (a) a large WWTP with anaerobic sludge digestion; and (b) a small WWTP where sludge is only dewatered. In a two-stage PHA-production system (biomass enrichment plus PHAs accumulation), the minimum PHAs cost would be 1.26 and 2.26 US$/kg PHA-crude for the large and small WWTPs, respectively. In a single-stage process, where a fraction of the secondary sludge (25%) is directly used to accumulate PHAs, the production costs would decrease by around 15.9% (small WWTPs) and 19.0% (large WWTPs), since capital costs associated with bioreactors decrease. Sensitivity analysis showed that the PHA/COD (Chemical Oxygen Demand) yield is the most crucial parameter affecting the production costs. The energy, methane, and sludge management prices also have an essential effect on the production costs, and their effect depends on the WWTP’s size.

Pulsed electric field application reduces carbapenem- and colistin-resistant microbiota and blaKPC spread in urban wastewater

Wastewater flows from metropolitan areas, especially those with healthcare inputs, can serve as transport reservoirs for the dissemination of clinically-relevant antimicrobial resistant bacteria (ARB) such as carbapenem- (CR) and colistin-resistant (CoR) strains. Pulsed electric field (PEF) is an emerging wastewater management tool for reducing bacterial loads without generating environmentally harmful byproducts, but it's ability to reduce ARB and their genetic determinants is not well reported. We collected 86, 10-L raw wastewater influent samples from a large metropolitan wastewater treatment plant in Columbus, Ohio and subjected them to low (34 kV cm−1 for 67 μsec) and high (36 kV cm−1 for 89 μsec) PEF treatment. We quantified the PEF effectiveness by measuring concentrations of total coliform bacteria, CR and CoR bacteria, and the epidemic carbapenemase gene, blaKPC, before and after PEF treatment. Utilizing marginal linear regression models with generalized estimating equations, we observed that low and high PEF treatment resulted in a 1.94 (95% CI 2.06–1.81; P < 0.001) and 2.32 (95% CI 2.46–2.18; P < 0.001) log reduction of total coliform bacteria concentrations, respectively. Low and high PEF treatment produced similar log reductions between CR E. coli (2.01 (95% CI 2.15–1.86; P < 0.001); 2.14 (95% CI: 5.30–4.61; P < 0.001)) and CR Enterobacteriaceae concentrations (1.55 (95% CI 1.70–1.41; P < 0.001); 1.86 (95% CI 2.05–1.68; P < 0.001)), and resulted in a 1.15 log (95% CI 1.38–0.93, P < 0.001) and 1.28 log (95% CI 1.54–1.03, P < 0.001) reduction of absolute blaKPC concentrations. Log CoR E. coli concentrations were reduced by 2.47 (95% CI 2.78–2.15; P < 0.001) and 2.52 (95% CI 2.91–2.15; P < 0.001) and CoR Enterobacteriaceae by 2.24 (95% CI 2.52–1.95; P < 0.001) and 2.50 (95% CI 2.89–2.11; P < 0.001) following low and high PEF application. PEF can be applied for wastewater management as an independent treatment method, particularly at critical control points, such as an on-site management of wastewater from hospitals or other healthcare facilities, or in series with other conventional methods to reduce total bacterial loads and concentrations of clinically-relevant ARB.

Engineered silver nanoparticle (Ag-NP) behaviour in domestic on-site wastewater treatment plants and in sewage sludge amended-soils

Untreated sludge from small-scale on-site domestic wastewater treatment systems (septic tanks) was spiked with 20, 60 and 100 nm silver nanoparticles (Ag-NPs) to investigate Ag-NP behaviour in these systems that are widely distributed in rural areas. In addition, the release of Ag-NPs from a previously spiked clay-rich loam reference soil (LUFA 2.4) was evaluated, in the presence and absence of untreated sludge, to simulate the common practice of sludge disposal by spreading on agricultural land. Single particle ICP-MS was used to determine Ag-NP size distribution and the results were compared with total Ag (Ag-NP and ionic) measured in acid digested samples. As documented previously for large municipal scale wastewater treatment plants, Ag-NPs are found to be overwhelmingly (~98%) retained in the sludge in these small-scale systems. The Ag-NP retention efficiency on the LUFA reference soil amended with sludge is approximately 10 times greater than that of LUFA soil alone (in the absence of sludge). For soil spiked with 60 nm Ag-NPs, the calculated average diameter of Ag-NPs in the supernatant, after 24 h was 45 ± 3 nm (dissolution rate 7.2E−06 mol/m2·h for 60 nm Ag-NP), smaller than that of supernatant from the combined sludge/soil system (52 ± 2 nm), indicating lower Ag-NP dissolution rates in the sludge-amended soil. This study provides new information about the leachability of Ag-NPs from septic tank sludge and suggests that the effluent and sludge from septic tanks are potential sources of both nano- and dissolved ionic-Ag to environmental waters.

Performance evaluation of submerged membrane bioreactor for model textile wastewater treatment

Submerged Membrane bioreactor (SMBR) is one of the last techniques that allow a high quality of treated industrial effluents by coupling biological treatment and membrane separation. Thus, this research was an effort to evaluate performance of a SMBR treating a model textile wastewater (MTWW). Different SMBR operating parameters like mixed liquor suspended solids (MLSS) and Dissolved oxygen concentration, hydraulic retention time (HRT), and nutrients addition (N and P) have been investigated. MTWW (influent to the SMBR) was generated using the reactive azo-dye, Novacron blue FNG (100mg/L feed concentration). Results of MTWW treatment using SMBR under optimal operating conditions (MLSS, 4.2-13.3g/L; HRT, 4 days; pH, 6.9-7.2; conductivity, 400-900 µS/cm and temperature, 19.4-22.2 °C) showed that COD and blue colour treatment performances are between 94-98% and 30-80%, respectively. It is concluded that SMBR can be used in large scale textile wastewater treatment plants to improve effluent quality in order to meet effluent discharge standards.

Assessing environmental impacts of large centralized wastewater treatment plants with combined or separate sewer systems in dry/wet seasons by using LCA

Rainfall can affect influent flow rate and compositions of wastewater, and thus further affect wastewater treatment performance and the effluent quality. This study aims to study the influence of rainfall on the environmental impacts of centralized wastewater treatment plants. The correlations between rainfall, and influent flow rate and compositions of wastewater in wet and dry seasons with two sewer systems, i.e. combined and separate sewer systems, were primarily established. Environmental impacts were assessed with life cycle assessment (LCA) to understand the temporal environmental burdens in wet and dry seasons. Functional units as per m3 treated wastewater (FU1) and as per kg PO43-eq. removed (FU2), respectively, were used to evaluate impacts of wastewater treatment to the environment. Strong correlation between rainfall and the influent flow rate was found in the wastewater treatment plants with either a combined sewer system (with Pearson correlation coefficient r at 0.66) or a separate sewer system (with r at 0.84), where r represents the strength of the association between two variables. The rainfall effect is more obvious on the eutrophication potential and global warming potential than on other environmental indicators while sewer system, i.e. combined or separate, seems not important in the two cases studied. Both wastewater treatment plants (WWTPs) show a lower environmental burden in the wet season than in the dry season partially due to the dilution of wastewater by using FU1. The WWTP receiving high strength wastewater, however, demonstrates higher environmental impacts in the wet season by using FU2 than FU1, due to the less efficient treatment caused by heavy rainfall. Meanwhile, it is found that environmental impacts from the WWTP receiving low strength wastewater have no difference when using either FU1 or FU2. The results indicate that the environmental burdens particularly eutrophication and global warming caused by WWTPs are dependent on the correlations of rainfall intensity with wastewater quantity and quality instead of combined or separate sewer system. This could be used to guide a stricter control of eutrophication in a more sensitive season in more vulnerable receiving waters.

Sustainable design of large wastewater treatment plants considering multi-criteria decision analysis and stakeholders’ involvement

The typical treatment scheme of a large municipal wastewater treatment plant (LWWTP) is almost always the result of design based on technical and economic criteria. Once a threshold in terms of population equivalent (PE) is reached, it is possible that additional sludge thermal treatment might be required. Aspects such as greenhouse gas (GHG) emissions and land use for the construction of the WWTP or the service landfill are considered marginal in current design practice; in a world that requires increasingly attention to the environment, these criteria cannot be ignored when defining the treatment scheme of a LWWTP. With the intent of providing a sustainable approach to design, this study aims to identify the best treatment scheme for a LWWTP with a 720,000 PE size. Methodologically, the study involves the development of an approach based on multi-criteria decision analysis (MCDA). Six alternative treatment schemes were considered; two simplified schemes, without primary sedimentation, with extended aeration activated sludge processes and aerobic sludge stabilization; four full schemes, with primary sedimentation and anaerobic sludge digestion. Some schemes differ for the organic loading rate applied; others for the use of sludge incineration. Subsequently, six evaluation criteria (ECs) such as GHG emissions, electricity consumption, running costs, WWTP planimetric area, surface for the service landfill, as well as WWTP as biorefinery have been considered. The weighting of the ECs involved the participation of the main stakeholders in such a decision-making process, following a bottom-up approach. The resolution of the MCDA problem allowed the identification of the full scheme based on primary sedimentation, biological activated sludge at low organic load (0.210 kgBOD5/kgVSS/d) and anaerobic sludge digestion as the best solution. The sensitivity analysis, able to indirectly take into account the multitude of decision makers involved, allowed corroborating the results. The obtained treatment scheme was different from that generally adopted in current design practice for LWWTPs.

Dishwashing detergents and their effects on respiration inhibition of activated sludge

Nowadays, many households in the Czech Republic have a dishwasher. Their use releases the remnants of the dishwashing detergents used therein into the sewerage network. These substances affect the activity and also the lifetime of microorganisms in wastewater treatment plants (WWTP). Research is focused on respiration inhibition of microorganisms contained in activation sludge from WWTP and their affected by dishwashing detergents. In view of Regulation No 259/2012 of the European Parliament and of the Council concerning the limitation of the total phosphorus content of dishwashing detergents (into force on 1 January 2017), there have been significant changes in the structure of these detergents. The article describes the effect of selected dishwashing detergents on respiratory inhibition of activation sludge from a large municipal WWTP Ostrava and a small municipal WWTP Michálkovice. Both of these WWTPs are owned by OVAK (Ostrava waterworks and sewerage). Subsequently, the research is focused on the comparison of obtained results. The highest variation in values were measured for sample 3, where the inhibition measured when testing a sludge from a large WWTP differed by up to 60% from that measured when testing a sludge from a small WWTP. The research also evaluates possible causes of respiration inhibition of microorganisms when testing specific sample solution.

Occurrence, seasonal variation, and environmental impact of phthalic acid esters in a large wastewater treatment plant located in Guangzhou, China

Occurrence, seasonal variation, and environmental impact of phthalic acid esters in a large wastewater treatment plant located in Guangzhou, China

Analysis of COD Fractions in Raw Wastewater Flowing into Small and Large Wastewater Treatment Plants

Analysis of COD Fractions in Raw Wastewater Flowing into Small and Large Wastewater Treatment Plants