Showing papers in "Water Practice & Technology in 2013"
TL;DR: Aerobic granular sludge technology can be regarded as the future standard for industrial and municipal wastewater treatment as discussed by the authors, and a growing number of institutes and universities focus their scientific research on this new technology.
Abstract: Aerobic granular sludge technology can be regarded as the future standard for industrial and municipal wastewater treatment. As a consequence, a growing number of institutes and universities focus their scientific research on this new technology. Recently, after extensive Dutch research and development effort, an aerobic granular biomass technology has become available to the market. Full scale installations for both industrial and municipal applications are already on stream, under construction or in design. The technology is distinguished by the name ‘Nereda®’ and based on the specific characteristics of aerobic granular sludge. It can be considered as the first mature aerobic granular sludge technology applied at full scale. It improves on traditional activated sludge systems by a significantly lower use of energy and chemicals, its compactness and its favorable capital and operational costs.
104 citations
TL;DR: In this paper, a method to recover struvite from digested sludge was developed at Stuttgart University, involving first an acidic dissolution of nutrients from digesting sludge followed by a precipitation step.
Abstract: Struvite precipitation for nutrient recovery from wastewater and sewage sludge has been attracting interest, due to the remarkable fertiliser quality of the product. A method to recover struvite from digested sludge was developed at Stuttgart University, involving first an acidic dissolution of nutrients from digested sludge followed by a precipitation step. The application was first tested in a pilot scale plant and recently upscaled to a semi-industrial size by constructing a recovery plant at a municipal wastewater treatment plant. The study reports on the technical features and the operation of the large-scale plant with a short overview on the pathway leading to the construction, as well as quality of the product.
25 citations
TL;DR: In this article, a pilot study was carried out in a waste water treatment plant to recover phosphorous by Struvite precipitation from anaerobic digester centrate by means of Ostara's Pearl technology with the objective to assess technically and economically the performance and reliability of this process treating sidestreams with different concentrations of phosphorous and also to assess the quality of the fertilizer obtained.
Abstract: A pilot study was carried out in a waste water treatment plant (WWTP) to recover phosphorous by Struvite precipitation from anaerobic digester centrate by means of Ostara's Pearl technology with the objective to assess technically and economically the performance and reliability of this process treating sidestreams with different concentrations of phosphorous and also to assess the quality of the fertilizer obtained. Different scenarios were studied: phosphorous inlet ranged from 31 to 150 mg PO4-P/L. The phosphorous removal varied from 60 to 81% depending on the influent, and the quality of the Struvite obtained was suitable to be used as a fertilizer. The economic assessment of implementing Struvite Pearl recovery process at full scale in WWTPs with anaerobic digestion (AD) and P-physicochemical or bio-P removal was carried out, taking into account investment (CAPEX) and operating costs (OPEX) of the Struvite recovery process and the economic savings due to phosphorous and ammonium removal in centrates. The results showed that with the current reagent strategies and investment costs, the Struvite recovery process was not economically feasible for WWTPs with AD and P-physicochemical removal. However, in the case of bio-P removal WWTPs with AD, the process can be an economic solution (pay back between 5 and 10 years, OPEX recovered due to the selling Struvite) which creates a high value re-cycled fertilizer and saves the environment due to the higher efficiency of the fertilizer usage.
22 citations
TL;DR: In this article, a description is given, of tools that were developed to aid the analysis of WDNs during situations of low or non-existent pressures, and testing of the tools revealed that they could represent network behaviour fairly accurately.
Abstract: On account of an ever increasing scarcity of potable water, ineffective water distribution networks (WDNs) and growing demand, several water distribution systems exhibit intermittent flow behaviour, either inevitably or under the deliberate action of operators, when they are expanded beyond their design capacities. This tendency is generally undesirable due to the fact that it leads to reduced service levels and consumer dissatisfaction. Moreover, due to inadequate system pressures and insufficient flows, the analysis of intermittent flow behaviour requires unconventional approaches, ultimately complicating network management. In this paper, a description is given, of tools that were developed to aid the analysis of WDNs during situations of low or non-existent pressures. Testing of the tools revealed that they could represent network behaviour fairly accurately.
17 citations
TL;DR: In this article, a study was conducted to produce Zinc chloride activated carbon from cassava peels which is a major solid waste from the cassava production process, and the results showed that CPAC could be adopted for treatment of cassava industry wastewater.
Abstract: Industrial waste disposal is a worldwide problem. It is necessary to manage production facilities and systems properly to prevent environmental degradation. The major aim of this study was to produce Zinc Chloride activated carbon from cassava peels which is a major solid waste from the cassava production process. The wastewater from cassava processing was treated using a peroxide oxidation process before being subjected to adsorption using Cassava Peel Activated Carbon (CPAC) at different activation levels. Results from the study shows that CPAC at activation ratio of 1:1 was the most effective as all parameters after adsorption with the exception of suspended solids fell below FEPA interim standard on discharge. The CPAC at 2:3 activation ratio also met the discharge standards but after 8 hrs of contact time. The result shows that CPAC could be adopted for treatment of cassava industry wastewater. Decontamination efficiency of the CPAC was 100% for Ni, Cd, Cr and CN at all activation levels while BOD 5 removal for no activation, 1:3, 2:3, 1:1 ZnCl 2 activation levels were 78.8, 85.9, 87.9 and 92.9% respectively. The CPAC exhibited the lowest values for Ca removal efficiency of 8.9, 8.9, 10.1 and 10.1% for no activation, 1:3, 2:3 and 1:1 activation levels respectively. Colour removal efficiency values were 33.3, 41.7, 41.7 and 50.0% respectively after 8 hrs of contact time.
17 citations
TL;DR: The objective of this work was to study the prevalence of antibiotic resistance phenotypes among total coliforms (TC), E. coli, E. faecalis and Salmonella spp.
Abstract: The objective of this work was to study the prevalence of antibiotic resistance phenotypes among total coliforms (TC), E. coli, E. faecalis and Salmonella spp. in the sewage treated effluents generated from three sewage treatment plants in Penang Malaysia. Among the isolates tested, TC and E. coli occurred high resistance for cephalexin (100 and 90.47%), ampicillin (80.93 and 95.23%) and ciprofloxacin (19.06 and 14.3%) compared to E. faecalis (42.86, 71.4 and 4.7%) and Salmonella spp. (59.8, 47.46 and 14.3%) respectively. All E. coli strains, 76.18% of TC, 66.66% of E. faecalis and 35% of Salmonella spp. were multi-resistant.
16 citations
TL;DR: The research highlighted a major issue: the need to review the Norwegian standard used to classify pipes from visual inspection, which consists on the standard being too pessimistic in the pipe classification leading to a much more negative figure of the overall network need for rehabilitation that it is in reality.
Abstract: Strategic use of condition monitoring to support rehabilitation planning of the Oslo wastewater network is the topic presented. The paper describes the process followed from investigating the quality of the data, selecting the final dataset for models calibration and finally modeling the prediction of the deterioration process under selected rehabilitation strategies. The model applied for the analysis is termed GompitZ and it based on the probabilistic theory of Markov chains; it defines the relationship between the current state and the expected service time of sewer pipes using Close Circuit TV inspections as classification input. The research highlighted a major issue: the need to review the Norwegian standard used to classify pipes from visual inspection. The problem consists on the standard being too pessimistic in the pipe classification leading to a much more negative figure of the overall network need for rehabilitation that it is in reality. By classifying the pipes as much more close to collapse than thy actually are, brings also to a too high estimation of the investment needs for rehabilitation plans. The research is currently focused on further developing the GompitZ tool by introducing the concept of ‘risk’ in the ranking of segments for prioritizing rehabilitations in long-term simulations. The choice of the strategy to undertake would be then based on a trade-off between costs, conditions and risk.
12 citations
TL;DR: In this article, the principal component analysis with a multiple linear regression receptor model was employed in quantitative source apportionment of particulate-associated polycyclic aromatic hydrocarbons (p-PAHs) with regard to particle size distribution in road-deposited sediment.
Abstract: This study showcases the source apportionment of particulate-associated polycyclic aromatic hydrocarbons (p-PAHs) with regard to particle size distribution in road-deposited sediment. The principal component analysis with a multiple linear regression receptor model was employed in PAHs quantitative source apportionment. Results show that two major contributors to sorption at the size fraction of 1000–400 μm were tentatively identified as vehicle emission (63.3%) and wood combustion (36.7%). Three major contributors to the size fraction of 400–100 μm were identified as coal combustion (65.4%), crankcase oil/vehicle emission (25.5%), and coal tar (9.1%). Three major contributors to the size fraction of 100–63 μm were identified as tire debris (67.3%), crankcase oil (15.0%), and coal tar (17.6%). The potential contributors in the size fraction 63–0.45 μm were identified as multiple sources (87.9%) and atmospheric deposition (12.1%). In addition, the highest ∑ 16 PAHs concentration was found in the smallest size fraction of 63–0.45 μm, where the highest B a PE and TEF values also occurred.
11 citations
TL;DR: In this article, a water-oil-surfactant simulation model had been established to simulate a surfactant enhanced aquifer remediation process, and a nonlinear optimization model was formulated for the minimum cost, and Kriging surrogate model was embedded into the optimization model as a constrained condition.
Abstract: Spillage of large amounts of Denser Nonaqueous Phase Liquids (DNAPLs) had resulted in serious pollution of groundwater resources throughout the world; a large number of studies had demonstrated surfactant-enhanced remediation is a more effective approach to remediate DNAPLs contaminations. In this paper, the remediation optimization process was carried out in three steps. Firstly, a water-oil-surfactant simulation model had been firstly established to simulate a surfactant enhanced aquifer remediation process. The Kriging surrogate model had been developed to get a similar input–output relationship with simulation model. In the final, a nonlinear optimization model was formulated for the minimum cost, and Kriging surrogate model had been embedded into the optimization model as a constrained condition. What is more, simulated annealing method was used to solve the optimization model and give the optimal Surfactant-Enhanced Aquifer Remediation strategy. The results showed Kriging surrogate model had reduced computational burden and make the optimization model easy to solve, and the optimal strategies gave an effective guide to contaminants remediation process.
10 citations
TL;DR: In this article, the authors discuss the technical approaches being evaluated in these projects and the lessons learned in the operation of the existing full-scale IPR facilities, as well as their own pilot-scale and demonstration-scale projects.
Abstract: While indirect potable reuse (IPR) has been used in southern California (USA) since the 1970s, the commissioning of the 265-megalitre-per-day Groundwater Replenishment System (GWRS) in Orange County (California) showed the region's commitment to utilizing reuse as a major source of potable water augmentation. The treatment process used at GWRS has become the benchmark on which California regulations were based and which other IPR facilities are measured against. As the cities of Los Angeles and San Diego move forward with their own IPR programs, they have commissioned pilot-scale and demonstration-scale projects to build on the lessons learned at the GWRS and to aid in developing future projects that are efficient, effective, and publicly supported. This paper will discuss the technical approaches being evaluated in these projects and the lessons learned in the operation of the existing full-scale facilities.
10 citations
TL;DR: In this article, the authors focused on the application of DTS in sewer systems with the aim of locating illicit connections, and especially on an automated way to analyze the large amount of data.
Abstract: Fibre-optic Distributed Temperature Sensing (DTS) is a widely used technique. The technique measures temperature with a high resolution and high frequency along cables with lengths up to kilometers. This paper focuses on the application of DTS in sewer systems with the aim of locating illicit connections, and especially on an automated way to analyze the large amount of data.
The automated procedure scans the data for sudden temperature changes that are not caused by rainfall. These changes are marked as possible illicit connections when temperature changes are significantly larger than noise levels in the measurements. By adding artificial spills to field measurements it is concluded that the procedure works for the defined spills. Also when applied to field measurements it is concluded that the automated procedure produces good results.
TL;DR: In this paper, the authors determined the autotrophic, heterotrophic and mixed denitrification rates via lab batch tests and determined the total nitrogen removal rate in a 6.5km long force main sewer via field study with calcium nitrate dosed at an average influent rate of 15.6 mg N/L.
Abstract: Discharging source-separated and nitrified urine into sewer helps to save cost and space in biological nitrogen treatment as in-sewer denitrification is induced. This unique denitrification process may become complicated in sewers with sulfide contamination as simultaneously autotrophic and heterotrophic denitrification possibly occur but may compete each other for nitrate in oxidation of sulfide and organics. The objective of this study is to estimate the mixed denitrification rate in a sulfide-contaminated sewer when nitrified urine (mainly nitrite and nitrate) is discharged. In this study two investigations were conducted: (1) determination of the autotrophic, heterotrophic and mixed denitrification rates via lab batch tests and (2) determination of the total nitrogen removal rate in a 6.5-km long force main sewer via field study with calcium nitrate dosed at an average influent rate of 15.6 mg N/L. The lab tests determined the rates of autotrophic, heterotrophic and mixed denitrification at 0.36 ± 0.06, 6.54 ± 0.04 and 1.99 ± 0.1 mg N/L/h, respectively, while the field study estimated the total in-sewer denitrification rate at 2.32 mg N/L/h in the sewer when sulfide was present. Simultaneously autotrophic and heterotrophic denitrification was found when sewage was contaminated with sulfide. However, nitrogen removal rate of heterotrophic denitrification was 3.3 times higher that of the mixed denitrification process. The results indicate that discharging source-separated and nitrified urine into sewer is meaningful to decentralized sewage treatment, especially when sulfide is absent in the sewer.
TL;DR: In this article, major ions were analyzed for twenty-five groundwater samples collected from diverse aquifer in Baishan mining, northern Anhui province, China, and the results showed that the diverse samples have vary ions inheriting from aquifer, samples from Sandstone aquifer (SA) is characterized by the high concentration of Na + + K +, for the feldspar weathering is dominant; Ordovician limestone aquifer waters have abundance Ca 2+ and Mg 2+, for dissolution of calcite and dolomite obviously; the dissolution
Abstract: Major ions were analyzed for twenty five groundwater samples collected from diverse aquifer in Baishan mining, northern Anhui province, China. Conventional graphical and multivariate statistical approach were completed to identify the hydro-geochemical process and water-rock interaction, that be combined with the Cluster Analysis (CA) and Fisher discriminant analysis to recognize the sealed samples, the result showed: the diverse samples have vary ions inheriting from aquifer, samples collected from Sandstone aquifer (SA) is characterized by the high concentration of Na + + K + , for the feldspar weathering is dominant; Ordovician limestone aquifer (OA) waters have abundance Ca 2+ and Mg 2+ , for the dissolution of calcite and dolomite obviously; the dissolution of calcite and other calcareous concretions are dominant in Taiyuan formation water (TA) and Quaternary aquifer (QA) for the high ratio of Ca 2+ /Mg 2+ , otherwise the varied content of SO 4 2– and HCO 3 − could distinguish the two aquifer water. Twenty five groundwater samples, containing six sealed samples, had been subdivided in to four groups by the CA, what are corresponded with four aquifers. Fisher discriminant functions were obtained and the efficiency was acceptable for the error rate 4% in all twenty five samples.
TL;DR: In this paper, the authors studied the physicochemical and microbiological characteristics of influent and effluent generated by the sewage treatment plant of Jodhpur city, India and found that high ambient temperature, long photoperiod and high intensity of light can be considered as the major factors for the removal of fecal indicators during the treatment.
Abstract: The objective of this study is to find out physico-chemical and microbiological characteristics of influent and effluent generated by the sewage treatment plant of Jodhpur city. The treatment plant was constructed in the year 2003–2004 and based on waste stabilization pond (WSP) system. The treatment capacity of the plant is 45 ML/d. Relationship between different physico-chemical and microbiological parameters were studied. After the treatment of wastewater in WSP, average removal of BOD, COD, TSS and TKN were 84.1, 53.4, 79.7 and 61.7% respectively. Average removal of Total Coliforms (TC), Fecal Coliforms (FC), E. coli and Fecal Streptococci (FS) were 2.79 logs, 2.47 logs, 1.65 logs and 1.58 logs respectively. Maximum efficiency of fecal bacteria removal was found during the summers (2.7 to 4.0 log units) and minimum in winters (1 to 1.8 log unit). Further correlation of temperature, pH and biological oxygen demand with TC, FC, E. coli and FS were studied. Among all these parameters temperature shows highest correlation with microbiological parameters as follows: TC (−0.85), FC (−0.62), E. coli (−0.65) and FS (−0.75). High ambient temperature, long photoperiod and high intensity of light can be considered as the major factor for the removal of fecal indicators during the sewage treatment. After treatment pH, BOD, COD, TSS and TKN were found within the permissible limit of Central Pollution Control Board, India. The observed values of fecal indicator organisms are higher than the permissible limit of World Health Organization (WHO). There are no maturation ponds in the treatment plant; construction of maturation ponds will provide better removal of fecal coliforms.
TL;DR: In this paper, the effects of environmental factors, roof materials and age of roof on some metals usually found in Domestic Roof-Harvested Rainwater (DRHRW) from southern Nigeria were investigated.
Abstract: The effects of environmental factors, roof materials and age of roof on some metals usually found in Domestic Roof-Harvested Rainwater (DRHRW) from southern Nigeria were investigated. Samples were collected in Ibadan (residential), Lagos (industrial) and Port-Harcourt (gas-flaring). Four roof types (corrugated-iron-sheet, long-span-aluminium, asbestos and step-tiles) and three ages of roof ( 10 years in service conditions) were considered. Sample preparations, handling and analysis were carried out using standard procedures. Enrichment-Factor, Transfer-Factor and Pollution-Load-Index were estimated to identify roof polluting severity, rate of transfer of each metal detected into the DRHRW as well as atmospheric contribution to the overall pollution effects observed. Metal enrichment was generally low indicating low metal transfer into DRHRW from the sites. Occasional moderate enrichment was recorded for Fe, Cu, Zn, Ca and Mg suggesting their natural presence in the environment. Extremely high enrichment observed for Pb and Cd in industrial and gas-flaring rainwater samples as compared with residential indicated that metal contaminations in these locations are higher compared to residential samples which serve as background. Rate of metal transfer from roof material to rainwater was generally low. Thus, the possible source of the metal contaminants found in DRHRW in the areas investigated was the atmosphere. Mean Pollution-Load-Index of 0.95, 0.99 and 1.06 for rainwater samples in Ibadan, Lagos and Port-Harcourt areas respectively suggested higher pollution load in gas-flaring than residential and industrial regions. Pollution-Load-Index applied to age and roof-type indicated that long-span-aluminium and asbestos roofs that are less than 5 years could contaminate rainwater.
TL;DR: The use of wastewater resulted in disease spread in roots and fruits (by cross-contamination) and further exploitation is necessary for microbial load reduction with wastewater application.
Abstract: Municipal wastewater may be used in agriculture but requires a careful monitoring of several hygiene parameters. The impact of direct application of treated wastewater in plant growth and development in hydroponically grown cucumber was studied. Cucumber seedlings used under 5 treatments of nutrient solution, which were basic nutrient solution (control), primary (PA) and secondary (SA) wastewater with or without nutrient solution enrichment (NS). The use of PA ± NS reduced plant height, leaf number and flowers produced as well as leaf size in cucumber plants but increased stem diameter. When SA ± NS used, no similar changes observed. The increased fruit number and fresh weight, when PA and SA used, resulted in increased yields as marked at the first week. The NS enrichment in PA reduced (up to 25%) plant yield while no differences observed in total fruit number among the treatments. No differences observed in plant biomass, root length and leaf chlorophyll levels among the treatments. The leaf photosynthetic rate and stomatal conductance increased in plant grown in PA ± NS and SA, but they did not differ in SA ± NS. The use of wastewater resulted in disease spread in roots and fruits (by cross-contamination). Further exploitation is necessary for microbial load reduction with wastewater application.
TL;DR: In this paper, multivariate statistical methods including factor and cluster analysis have been presented for identification of groundwater mixing status in the Renlou coal mine, northern Anhui Province, China.
Abstract: Identification of groundwater mixing and calculation of the mixing ratios between aquifers are important work for hydrological studies and safety of coal mining. In this study, multivariate statistical methods including factor and cluster analysis have been presented for identification of groundwater mixing status in the Renlou coal mine, northern Anhui Province, China. The methods include three steps: identification of hydraulic connection between aquifers by using factor score plots in combination with Q-mode cluster analysis, selection of end members and mass balance calculation for revealing mixing ratios. The hydraulic connection between loose layer and limestone aquifers have been identified in the Renlou coal mine, and three representative end member water samples, as well as mixed samples have been identified. Moreover, the mixing ratios for mixed samples are also calculated. The results indicate that the methods can be used for identification of mixing and quantification of mixing ratios in groundwater systems.
TL;DR: In this paper, the authors examined the effect of irrigation with several type of treated domestic wastewater on production of carnations and found that nutrients and micro-elements contained in treated wastewater had as a result positive effect on characteristics of carnation.
Abstract: The reuse of domestic wastewater for irrigation of floriculture crops is a very promising option in water-scarce areas. On the other hand, there are concerns about the effect of that kind low-quality water on plant growth. The present work examined the effect of irrigation with several type of treated domestic wastewater on production of carnations. Potted plants were irrigated with primary treated, secondary treated and tertiary treated wastewater as well as with water and water with fertilizer. The results shown that carnations can be irrigated with treated wastewater as the growth and quality of plant is equal or better compared with water. Furthermore, it was found that nutrients and micro-elements contained in treated wastewater had as a result positive effect on characteristics of carnations.
TL;DR: In this paper, the authors evaluated a proposed system of water reuse at a Kraft pulp and paper plant in Brazil, based on a survey of water quality required by its consumption points, supplied by its water treatment plant.
Abstract: The reuse of wastewater by the pulp and paper industry reduces environmental impacts by contributing to raw water conservation, thereby making a greater volume of fresh water available for nobler purposes, and reducing wastewater treatment. This study evaluated a proposed system of water reuse at a Kraft pulp and paper plant in Brazil, based on a survey of water quality required by its consumption points, supplied by its water treatment plant. Results after ultrafiltration included: turbidity of 0,3 NTU and pH 7,5, average values of BOD 66,4 mg/L, COD 9,6 mg/L and the colour of 280,5 ppm Pt were measured after ultrafiltration. The ultrafiltered wastewater was considered available for reuse, and its quality was compared with that of the water supplied by the water treatment plant, which provided for the classification of potential reuse points. Water colour was identified as the limiting factor for reuse; thus the reuse points were two Kraft paper machines, and the water flow to the liquid ring formations that generate the vacuums inside nineteen pumps for these two machines. The advantages of this proposal for water reuse include: ultrafiltered water quality sufficient for the vacuum pumps, the small distance between the point of reused water generation and the paper machines section, and the reused water has no contact with the final product. The calculated cost and return time for the water reuse system was US$ 607.020,00 in 15 years.
TL;DR: In this article, a selection of WDUs were acquired and a series of standardised tests were performed on a variety of food groups to assess whether the output of these units would represent a potential food resource for rats in sewers.
Abstract: Sewer Rats ( Rattus norvegicus ) are opportunist occupiers of parts of underground sewerage networks. Their occupation in part depends upon their ability to scavenge food particles from faecal matter in the sewer flow. Food Waste Disposal Units, also called Garbage Grinders or Waste Macerators, are relatively uncommon in the United Kingdom (UK) but may become more common as pressure is put on other methods of waste disposal. Since these units put undigested food into the sewer network, some assessment needed to be made on any potential impacts on the sewer rodent population. This is important since policy relating to the acceptance of waste disposal units (WDUs) was based upon outputs. A selection of WDUs were acquired and a series of standardised tests were performed on a variety of food groups to assess whether the output of these units would represent a potential food resource for rats in sewers.
These results are presented graphically in the text, and show that a large proportion of the output would be available to rats.
TL;DR: In this article, the authors optimize the biodegradation of polyvinyl alcohol (PVA) containing actual textile wastewater for a sustainable treatment solution, where the maximum aeration was essential to achieve a high degradation rate, where as stirring enhances further degradation and foam control.
Abstract: The aim of this work was to optimize the biodegradation of polyvinyl alcohol (PVA) containing actual textile wastewater for a sustainable treatment solution. The isolated microbial consortia of effective PVA degrader namely Candida Sp. and Pseudomonas Sp., which were responsible for symbiotic degradation of chemical oxidation demand (COD) and PVA from desizing wastewater. In the process optimization, the maximum aeration was essential to achieve a high degradation rate, where as stirring enhances further degradation and foam control. Batch experiments concluded with the need of 16 lpm/l and 150 rpm of air and stirring speed respectively for high rate of COD and PVA degradation. Optimized process leads to 2 days of hydraulic retention time (HRT) with 85–90% PVA degradation. Continuous study also confirmed above treatment process optimization with 85.02% of COD and 90.3% of PVA degradation of effluent with 2 days HRT. This study gives environment friendly and cost effective solution for PVA containing textile wastewater treatment.
TL;DR: In this paper, the influence of sampling strategy on the quality of locally calibrated UV-VIS probe measurements in combined sewer overflows (CSO) and the receiving river was studied. But, the results showed that the use of the global calibration led to errors of at least 30 and 45% for CSO load and river concentration of chemical oxygen demand (COD), respectively.
Abstract: The presented work studies the influence of the sampling strategy on the quality of locally calibrated UV-VIS probe measurements in combined sewer overflows (CSO) and the receiving river. Results indicate that UV-VIS spectrometers are not able to provide reliable measurements of water quality in urban stormwater without being calibrated to local conditions with laboratory analyses of water samples. The use of the global calibration (supplied by the manufacturer) led to errors of at least 30 and 45% for CSO load and river concentration of chemical oxygen demand (COD), respectively. Even with reliable local calibration, COD loads contained significant uncertainties close to 20%. Uncertainties in COD load and concentration decrease below 30% if more than 15–20 samples (i.e. 3 and 4 stormwater events) are sampled for local calibration. The effort and associated sampling costs to gain more than 15–20 samples are much less effective, since load and concentration uncertainties remain relatively stable with an increasing number of samples used for the calibration. The presented analysis aims at supporting practitioners in the planning, operation and calibration of UV-VIS spectrometer probes.
TL;DR: In this paper, an analytical campaign was conducted on different drinking water treatment lines in order to characterize filter backwash water and assess the impact of recycling this water at the head of the plant, which may increase the concentration of parameters such as turbidity, suspended solids, metals from coagulants and protozoa.
Abstract: Analytical campaigns were conducted on different drinking water treatment lines in order to characterize filter backwash water and assess the impact of recycling this water at the head of the plant. The pollutants identified in this water are essentially in the form of particles. Recycling this water may consequently increase the concentration of parameters such as turbidity, suspended solids, metals from coagulants and protozoa. On the other hand, no release of pesticides nor significant generation of disinfection by-products was observed during filter backwash with chlorinated water, in the conditions applied in France for chlorination. A modeling approach based on the mass balance of Cryptosporidium oocysts was applied to estimate the impact of recycling on oocysts concentration in the inlet water. A risk of infection was then assessed for each recycling scenario. A similar approach was also applied for amoebae, which have the capacity to colonize filter media, and for metal residues from coagulants. The results of this study demonstrate that two different situations have to be considered separately: • In the case of treatment lines composed of separate sedimentation and filtration steps, recycling at the head of the treatment process, even with no treatment, has no significant consequence on the microbial quality of the inlet water, and generates no additional health risk for the consumer. • In the case of treatment lines with no sedimentation step (direct filtration or UF used alone), recycling untreated water generates an excess of risk for the consumer which is not acceptable. Adding a coagulation / sedimentation step in the recycling circuit is sufficient in that case to keep the risk within acceptable limits.
TL;DR: In this paper, a plant-wide approach to modeling and simulation of a full-scale activated sludge (AS) wastewater treatment plant (WWTP) is presented, and the calibration strategy, verification and predictive capacity of the model are discussed.
Abstract: In last decade the focal point of the activated sludge (AS) modelling shifted from a secondary-treatment to a plant-wide level. This new approach offers more possibilities, therefore demands more effort and expertise from a modeller. This paper presents a plant-wide approach to modelling and simulation of a full-scale AS wastewater treatment plant (WWTP). The construction and routine operational data of the full-scale Central WWTP in Gliwice (Poland) were used in this study to develop an integrated model of the water and sludge lines of the plant. The core of the plant model was the Activated Sludge Model No.1 (ASM1), which combined with sub-models of the other processes, was implemented in the WEST ® Software version 3.7.6. The calibration strategy, verification and predictive capacity of the model are discussed. The calibrated model permitted acceptable accuracy of the simulation, yet limited data restrained its scope. Thus, the obtained mathematical description of the plant is a preliminary yet sound basis for a more versatile model. The model limitations and opportunities for its further applications and development are discussed.
TL;DR: In this article, a soft sensor for volatile solids (VS) is developed using data from an industrial process and compared with the results from a simulation study where feed flow and biogas production rate are used for modelling VS.
Abstract: The lack of instrumentation in anaerobic digestion processes is a key bottleneck as sensors and analysers are necessary to reduce uncertainty related to the initial conditions, kinetics and the input concentrations of the process. Without knowledge of the process conditions, the process is inevitably difficult to control. This paper looks into the potential for developing a soft sensor for volatile solids (VS), an important variable that is currently only monitored offline. A VS inferential sensor is developed using data from an industrial process and compared with the results from a simulation study where feed flow and biogas production rate are used for modelling VS.
TL;DR: The potential of these natural coagulants were obtained by means of jar test study with initial turbidities of 192 NTU (High) and 28 NTU(Low).
Abstract: Coagulation being a cost-effective method is best suited for water treatment in rural areas. Natural coagulants suited for the simultaneous removal of turbidity and hardness were investigated. In this study, the seeds of Strychnos Potatorum , the pads of Cactus Opuntia and mucilage extracted from the fruits of Coccinia Indica in synthetic turbid water were used to promote coagulation. The mechanism of turbidity removal by the use of natural coagulants was based on adsorption and charge neutralization. In addition, the adsorption mechanism of hardness removal in hard water conforms to both Langmuir and Freundlich adsorption models. Therefore, for hard water the natural coagulants tend to adsorb hardness and form a net like structure followed by turbidity removal by sweep flocculation. The potential of these natural coagulants were obtained by means of jar test study with initial turbidities of 192 NTU (High) and 28 NTU (Low). It was found that the natural coagulants can be more efficiently used for high turbid waters. Hardness removal efficiency was found to increase with the increase in coagulant dosage.
TL;DR: In this paper, a new method was used to start Arak activated sludge WWTP up, which took in advantages of the other methods, such as less loading, less foam forming, no bacteriologic and chemical problems, better process control, using less seed, saving costs in sludge transport and avoiding relevant problems.
Abstract: Starting up a wastewater treatment plant (WWTP) is one of the most important stages of operation. A new method was used to start Arak activated sludge WWTP up, which took in advantages of the other methods. Primarily just one of the basins was in the lane and wastewater entered the plant part by part. At first 1/30, second week 1/15, third week 1/6, and fourth week 1/3 of total inflow came to the plant. Observing little progress of biomass gain, some sludge from a similar treatment plant was added to the system, as seed. This procedure continued so the MLSS of the system, attained the 1/3 total design MLSS which was design MLSS of one basin. In the next two weeks, by using developed sludge of the self-system the second and third basins came in the lane and inflow increased to 2/3 and total flow, respectively. Finally after two months of beginning the start-up and one month after adding the seed total desired biomass was developed and the plant started to waste sludge. Because of cold weather start-up period took a longer time than expected. But even before developing biomass environment friendly results were achieved. After attaining design MLSS, BOD5 and COD removal from 40% and 60% increased to 90% and TSS removal from 70% reached to 96%. Less loading, less foam forming, no bacteriologic and chemical problems, better process control, using less seed, saving costs in sludge transport and avoiding relevant problems were the main advantages of this method.
TL;DR: In this paper, an early warning system (EWS) called EPIGONE is proposed to detect dry weather overflows in the vicinity of throttle structures in sewer systems. But it is not suitable for large scale deployment.
Abstract: This study presents the development of an Early Warning System (EWS) called EPIGONE focusing on the detection of dry weather overflows in the vicinity of throttle structures in sewer systems. Throttle structures are considered as vital parts of a sewer system as they are control sections limiting flow rates to a designed operational value. Because these structures are by definition prone to potential clogging or blockages, a close follow-up of the daily operation by an EWS facilitates increased vigilance or even alarm. Primary goal of EPIGONE is to alert operators and thus allow fast intervention in case of suspected failures of these structures within a settled timeframe. EPIGONE combines overflow water level measurements with rainfall radar information to determine Combined Sewer Overflow (CSO) activity during dry weather as this dual condition will indicate malfunctioning. This combination of measurements was found to be the most cost effective set-up to deploy on a large scale. Water level data are recorded and logged on-site and sent to a central controller via GSM/GPRS, where an algorithm determines dry weather overflow conditions. Rainfall radar data are used as criterion to decide on dry weather conditions. From there on alarms are sent out to multiple recipients via e-mail and/or text messages (SMS). Next to this, it is obvious that this system can also be used for ‘regular’ wet weather CSO monitoring.
TL;DR: In this article, a dual-media biological filtration is used to achieve effluent concentrations of total suspended solids (TSS) ≤ 2 mg/L and NO 3 -N ≤ 5 mg/l in a municipal wastewater treatment plant.
Abstract: Operation of a pilot-scale dual-media biological filter as post-denitrification step in a municipal wastewater treatment plant was investigated for 28 months. In order to identify key design parameters, filtration rate, external carbon dosing concentration and strategy as well as backwash frequency were varied. The results show that dual-media biological filtration is able to achieve effluent concentrations of total suspended solids (TSS) ≤2 mg/L and NO 3 -N ≤ 5 mg/L. TSS removal also leads to a reduction of particulate bound phosphorus and chemical oxygen demand without dosing any precipitant. Soluble reactive phosphorus is required for growth of the denitrifying bacteria and reduced from 0.4 to 0.3 mg/L in the filter effluent, corresponding to approximately 0.02 g P/g NO x -N removed. Depending on NO x -N loading and carbon dosage, average denitrification rates of 0.5–1.0 kg NO x -N/m 3 *d were achieved in different operational phases. Seasonally varying nitrite formation and breakthrough in the filter effluent were observed and could not be controlled by adjusting carbon dosage and backwash frequency. Effective operational strategies to prevent nitrite breakthrough at NO x -N loads in the range of 1–2 kg NO x -N/m 3 *d and high influent O 2 levels are therefore needed.
TL;DR: In this article, a new inventory system has been developed to estimate GHG emissions by domestic WWTP, resulting from direct and indirect activities, and the inventory is started for Imhoff tanks, which constitute 12 percent of all domestic treatment plants in Malaysia.
Abstract: Domestic wastewater treatment plant (WWTP) is one of the entities that emit the greenhouse gas (GHG) to the environment because of microbial breakdown of the organics in human waste, and the use of electricity to operate the treatment plant itself. The first GHG inventory in Malaysia has provided a good foundation for the development of a more comprehensive national inventory. However, due to the lack of detail data from actual plant, Malaysia can only produce imprecise estimates for domestic wastewater. Therefore, there is a need to develop a proper database since based on various real plant characteristics and operating conditions, the actual values of GHG emissions from domestic wastewater in Malaysia could be different from other countries. In this study, a new inventory system has been developed to estimate GHG emissions by domestic WWTP, resulting from direct and indirect activities. Referring to the Intergovernmental Panel on Climate Change approach in 2006, the inventory is started for Imhoff tanks, which constitute 12 percent of all domestic treatment plants in Malaysia. The inventory gives preliminary overview on estimation of GHG emissions from onsite domestic treatment plant when treating wastewater for different Population Equivalent (PE) and Biological Oxygen Demand (BOD) loading.