Secondary Clarifier Research Articles

Evaluation and improvement of wastewater treatment plant performance using BioWin

In this study, the activated sludge model implemented in the BioWin® software was validated against full-scale wastewater treatment plant data. Only two stoichiometric parameters (Yp/acetic and the heterotrophic yield (YH)) required calibration. The value 0.42 was used for Yp/acetic in this study, while the default value of the BioWin® software is 0.49, making it comparable with the default values of the corresponding parameter (yield of phosphorus release to substrate uptake \((Y_{PO_4 } )\)) used in ASM2, ASM2d, and ASM3P, respectively. Three scenarios were evaluated to improve the performance of the wastewater treatment plant, the possibility of wasting sludge from either the aeration tank or the secondary clarifier, the construction of a new oxidation ditch, and the construction of an equalization tank. The results suggest that construction of a new oxidation ditch or an equalization tank for the wastewater treatment plant is not necessary. However, sludge should be wasted from the aeration tank during wet weather to reduce the solids loading of the clarifiers and avoid effluent violations. Therefore, it is recommended that the design of wastewater treatment plants (WWTPs) should include flexibility to operate the plants in various modes. This is helpful in selection of the appropriate operating mode when necessary, resulting in substantial reductions in operating costs.

2 Steps to Clarity – Un-denitrifying Secondary Sedimentation Clarifiers

2 Steps to Clarity – Un-denitrifying Secondary Sedimentation Clarifiers

Flocculation-Flotation vs. MBR for High MLSS Secondary Clarification

Flocculation-Flotation vs. MBR for High MLSS Secondary Clarification

Using Existing Facility to Maximize the Wet Weather Treatment Capacity of the Akron, Oh Water Reclamation Facility: Optimizing Existing Secondary Clarifiers

Using Existing Facility to Maximize the Wet Weather Treatment Capacity of the Akron, Oh Water Reclamation Facility: Optimizing Existing Secondary Clarifiers

The Impact of Depth on Secondary Clarifier Performance – An Industrial Perspective

The Impact of Depth on Secondary Clarifier Performance – An Industrial Perspective

On The Relationship between Suspended Solids of Different Size, the Observed Boundary Flux and Rejection Values for Membranes Treating a Civil Wastewater Stream.

Membrane fouling is one of the main issues in membrane processes, leading to a progressive decrease of permeability. High fouling rates strongly reduce the productivity of the membrane plant, and negatively affect the surviving rate of the membrane modules, especially when real wastewater is treated. On the other hand, since selectivity must meet certain target requirements, fouling may lead to unexpected selectivity improvements due to the formation of an additional superficial layer formed of foulants and that act like a selective secondary membrane layer. In this case, a certain amount of fouling may be profitable to the point where selectivity targets were reached and productivity is not significantly affected. In this work, the secondary clarifier of a step sludge recirculation bioreactor treating municipal wastewater was replaced by a membrane unit, aiming at recovering return sludge and producing purified water. Fouling issues of such a system were checked by boundary flux measurements. A simple model for the description of the observed productivity and selectivity values as a function of membrane fouling is proposed.

Multispecies acute toxicity evaluation of wastewaters from different treatment stages in a coking wastewater-treatment plant.

Coking wastewater contributes approximately 5% of the total discharge volume of industrial wastewaters every year in China. The toxicity of coking wastewater to aquatic organisms is still unknown. The authors evaluated the toxicity of wastewater from different treatment stages in a coking wastewater treatment plant, South China, using 5 test species belonging to different trophic levels: luminous bacteria, green alga, a crustacean, duckweed, and zebrafish embryos. The raw influent displayed the highest toxicity to the test species, with toxic units ranging from 16.2 to 1176. The toxicity in the wastewater was then gradually removed by sequential primary treatment, biological fluidized-bed treatment, and secondary clarifier treatment. The toxic unit of the final effluent was reduced to 2.26 for the green alga (Pseudokirchneriella subcapitata) and to 0 for the other 4 organisms. Quantitative analysis of metals and polycyclic aromatic hydrocarbons (PAHs) and qualitative scanning by gas chromatography-mass spectrometry showed the presence of a variety of pollutants in the coking wastewaters. Multivariate statistical analysis revealed that the toxicity in the coking wastewater was correlated to the chemical oxygen demand, total nitrogen, ammonia nitrogen, volatile phenols, sulfide, metals (Cr, As, Sb, Hg, Pb, and Ni), and ΣPAHs. Based on the results, it is required to set a safety emission limit value for the discharge of coking wastewater to protect aquatic organisms in the receiving water bodies.

N2O emissions from secondary clarifiers and their contribution to the total emissions of the WWTP.

Recent studies have indicated that the emissions of nitrous oxide, N2O, constitute a major part of the carbon footprint of wastewater treatment plants (WWTPs). Denitrification occurring in the secondary clarifier basins has been observed by many researchers, but until now N2O emissions from secondary clarifiers have not been widely reported. The objective of this study was to measure the N2O emissions from secondary clarifiers and weigh the portion they could represent of the overall emissions at WWTPs. Online measurements over several days were carried out at four different municipal WWTPs in Finland in cold weather conditions (March) and in warm weather conditions (June-July). An attempt was made to define the conditions in which N2O emissions from secondary clarifiers may occur. It was evidenced that large amounts of N2O can be emitted from the secondary clarifiers, and that the emissions have long-term variation. It was assumed that part of the N2O released in secondary clarification was originally formed in the activated sludge basin. The emissions from secondary clarification thus seem to be dependent on conditions of the nitrification and denitrification accomplished in the denitrification-nitrification process and on the amount of sludge stored in the secondary clarifiers.

UV resonance Raman spectroscopy: a process analytical tool for host cell DNA and RNA dynamics in mammalian cell lines

AbstractBACKGROUNDRecent advances in Raman spectroscopy have resulted in the development of rapid, in situ Raman probes that can identify and allow the assessment of the quality of complex constituents in mammalian cell culture. One specific Raman technique, UV resonance Raman (UVRR) spectroscopy, has potential as a probe for residual cellular DNA and RNA in mammalian cell culture medium.RESULTSVariations in DNA and RNA UVRR spectral profiles of medium‐cellular footprint samples were identified and related to time of harvest and increased cell lysis that is associated with a loss in cell viability. Increased DNA and RNA were also observed in the cell culture supernatant in response to sodium butyrate treatment. Variation in DNA and RNA profiles as a result of both primary and secondary clarification methods during downstream bioprocessing could also be determined with UVRR spectroscopy.CONCLUSIONSThis study has demonstrated the utility of UVRR spectroscopy as a tool to monitor variations in residual DNA and RNA that may contaminate cell culture medium. Application of this technique has the potential for both improvement of recovery techniques and assurance of reliable clearance of DNA/RNA to acceptable safety levels. © 2014 Society of Chemical Industry

Impact of approach used to determine removal levels of drugs of abuse during wastewater treatment

In this study the levels of 19 drugs of abuse were estimated throughout a wastewater treatment plant using polar organic chemical integrative samplers (POCIS), 24h composite samples and grab samples. Overall removal efficiencies and removals in between each treatment unit were calculated using load data for each sampling technique as well as removals that take into account the hydraulic residence time distribution of the treatment plant (time-shifted mass balancing approach). Amphetamine-type stimulants, cocaine and its major metabolite, benzoylecgonine and opioid levels determined with 24h composite samples were generally comparable to those obtained with POCIS and grab samples. Negative mass balances resulting from the estimation of overall removal efficiencies by POCIS, day-to-day mass balancing of 24h composite and grab sample data did not occur when the hydraulic retention time (HRT) distributions of the plant were taken into account for calculation. Among the compounds investigated, cocaine exhibited the highest overall removal (90%) while codeine had the lowest with 13%, respectively. Sampling between the treatment units revealed that highest removal occurs during biological treatment as compared to primary or secondary clarification. Methylenedioxyamphetamine (MDA), fentanyl, dihydrocodeine and heroin were not detected in wastewater at any of the sampling locations at the treatment plant regardless of the sampling technique. The study demonstrates the benefits of applying the time-shifted mass balancing approach to the calculation of removals of drugs of abuse during wastewater treatment.

Quantification method of N2O emission from full-scale biological nutrient removal wastewater treatment plant by laboratory batch reactor analysis

This study proposes a simplified method for the quantification of N2O emission from a biological nutrient removal wastewater treatment plant (WWTP). The method incorporates a laboratory-scale batch reactor which had almost the same operational (wastewater and sludge flow rates) condition of a unit operation/process of the WWTP. Cumulative N2O emissions from the batch reactor at the corresponding hydraulic retention times of the full-scale units (primary and secondary clarifiers, pre-anoxic, anaerobic, anoxic and aerobic basins) were used for the quantification of N2O emission. The analysis showed that the aerobic basin emitted 95% of the total emission and the emission factor (yield) reached 0.8% based on the influent nitrogen load. The method successfully estimated N2O emission from the WWTP and it has shown advantages in measurement time and cost over the direct field measurement (floating chamber) method.

CFD와 PIV test를 통한 원형 2차침전지 유입 및 유출배플 형상 최적화

The influent and effluent baffle configurations seriously affect the hydraulic characteristics of the secondary clarifier in wastewater treatment plant. In this study, those baffle configurations were optimized by computational fluid dynamics(CFD) analysis and particle image velocity(PIV) test in order to obtain uniform flow in inlet region and to minimize upflow velocity in outlet region of the secondary clarifier. Theoretical analysis using CFD showed that more uniform flow could be accomplished when the influent baffle was located closely to the inlet opening. Effects of effluent baffle configuration on the upflow velocity in the outlet region of the secondary clarifier were analyzed with four types of effluent baffles which are widely adopted for secondary clarifier design. From the CFD analysis, McKinney baffle(EB-2) was estimated to be the most effective for restraining the upflow velocity in the outlet region and these trends were identified by PIV tests. In addition, the McKinney baffle showed the most uniform overflow velocity distribution around the weir.

Use of talc for filamentous bulking control in effluent treatment plant

One of the main existing operational problems in activated sludge effluent treatment processes is the poor sedimentation of the biological sludge in the secondary clarifiers. This poor settleability of the sludge is, generally, associated with excessive growth of filamentous bacteria in the bioreactor causing sludge filamentous bulking. In Brazil, many pulp and paper mills have faced problems related to sludge filamentous bulking in their effluent treatment plants experiencing a significant reduction in COD and BOD removal efficiency and a loss of suspended solids in the treated effluent. The addition of talc to increase floc density for the control of filamentous bulking has been studied. The objective of this study was to test the use of talc for the control of filamentous bulking. The bio-sludge used was obtained from a recycling paper mill and had an abundance of filamentous bacteria Type 021N. The experiment consisted of five bioreactors operating batch wise with sludge age of ten days. Different talc applications were used: 0%, 25%, 50%, 75% and 100% in relation to the total suspended solids in the aeration tank. The following analyses were carried out to monitor the system: suspended solids, sludge volumetric index (SVI) and chemical oxygen demand. Successive additions of talc contributed for the reduction of IVL. Dosages of 75% and 100% showed to be most efficient to improve settleability of the sludge. The presence of talc did not interfere with biological activity of the sludge. However, it was observed an increase of the total suspended solid concentration in the aeration tank. The addition of talc had a temporary effect on sludge settleability, so it was necessary to add repeatedly talc in the reactor in order to maintain a low sludge volumetric index.

Occurrence and removal of benzotriazole ultraviolet stabilizers in a wastewater treatment plant in China.

Benzotriazole ultraviolet stabilizers (BZT-UVs) have previously been found in sludge from wastewater treatment plants (WWTPs), which might be potential sources of BZT-UVs to the surrounding environment. In this work, the occurrence and fate of seven emerging 2-hydroxyphenyl substituted BZT-UVs were investigated in a Chinese WWTP. This group of hydrophobic BZT-UVs possess log Kow values ranging from 4.31 to 7.67 which could be associated with their fate in WWTPs. Field samples including 24 h flow composites of influent, effluent and grab sludge samples from different treatment processes were collected and analyzed. Concentrations of BZT-UVs dissolved in aqueous-phases were in the range of 4.88±1.35 (UV-234) to 34.5±12.4 ng L(-1) (UV-P) in the primary influent, while only UV-P and UV-328 were detected in the final effluent at concentrations of 10.5±6.59 and 2.74±1.73 ng L(-1), respectively. Considering the amount of target BZT-UVs adsorbed to total suspended solids (TSS), the daily mass flux in the primary influent of the WWTP ranged from 22.3 g day(-1) (UV-P, 7.99%) to 74.0 g day(-1) (UV-234, 26.5%). Total removal efficiency of the integrated treatment process ranged from 89.7% for UV-P to 99.7% for UV-234 suggesting nearly complete removal. Organic solid sedimentation in primary and secondary clarifiers was the dominant elimination route for BZT-UV analogues, which constituted 96.3% of the total removal efficiency. Advanced treatment (using ultraviolet disinfection) in this plant might further contribute to the high removal efficiencies (ranging from 19.6% to 77.3%).

Rheology Measurements for Online Monitoring of Solids in Activated Sludge Reactors of Municipal Wastewater Treatment Plant

Rheological behaviour of recycled sludge from a secondary clarifier of a municipal wastewater treatment plant was studied by using the rate controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device NV. The tests (hysteresis cycles) were performed under continuous flow conditions and following an ad hoc measurement protocol. Sludge shear stress versus shear rate curves were fitted very satisfactorily by rheological models. An experimental equation correlating the solid concentration of sludge to relative viscosity and fitting satisfactorily flow curves at different Total Suspended Solids (TTS%) was obtained. Application of the empirical correlation should allow the monitoring of the proper functioning of a wastewater treatment plant measuring viscosity of sludge.

Novel method for sludge blanket measurements

The most widely used methods for sludge blanket measurements are based on acoustic or optic principles. In operation, both methods are expensive and often maintenance-intensive. Therefore a novel, reliable and simple method for sludge blanket measurement is proposed. It is based on the differential pressure measurement in the sludge zone compared with the differential pressure in the clear water zone, so that it is possible to measure the upper and the lower sludge level in a tank. Full-scale tests of this method were done in the secondary clarifier at the waste water treatment plant in Hecklingen, Germany. The result shows a good approximation of the manually measured sludge level.

Мікробоценози стічних вод Львова на різних етапах очищення

The aim of this work was to investigate some physiological groups of microorganisms which are components of wastewater microbiocenoses. Microorganisms were grown in Petri dishes containing 20–30 ml agar selective medium and in 25 ml tubes at a temperature +30 ºC. The selective media were: wort agar for microscopic fungi and yeasts, Hutchinson medium for the cellulose-destroying microorganisms, starch-ammonium medium for microorganisms that can utilize mineral nitrogen forms, Postgate B medium for sulfate-reducing bacteria, Vinogradsky medium for nitrifying bacteria, Ashby medium for the nitrogen-fixing bacteria, Chapek medium for the actinomycetes. 1 mM Cr (VI) (104 mg/l) in the form of К2Cr2О7 was added to the medium. The number of colonies was determined by the Koch method. We studied wastewater microbocenoses of Lviv city at various stages of purification. We showed that the quantitative and qualitative composition of microorganisms differed significantly in primary and secondary clarifiers, the aerotank and sludge at different stages of sewage treatment. In the initial stages of purification, in the primary sump, bacteria that reached the treatment plant with sewage were found. Nitrifying bacteria (7.1 × 106colony forming units (CFU)/ml), nitrogen-fixing bacteria (9.0 × 106CFU/ml), and fungi (3.4 × 106 CFU/ml) dominated. The qualitative composition of microorganisms in primary clarifiers and the aerotank was similar, but their number in the aerotank was significantly higher than in the primary sump: 1.5 × 107 CFU/ml of nitrifying bacteria, 1.4 × 107CFU/ml of nitrogen-fixing bacteria, 6.7 × 106CFU/ml of fungi. The ratio of different physiological groups of microorganisms in the active sludge changed significantly. The predominant microorganisms were those that assimilate mineral forms of nitrogen (65%), their number was 1.6 × 108CFU/ml. In the secondary clarifier, the largest group was cellulose-destroying microorganisms (6.0 × 105CFU/ml). However, their numbers in the secondary sump were lower compared to their numbers in the aerotank and sludge (1.5–3.9 × 106CFU/ml). Among the representatives of various physiological groups of bacteria a significant number of chromium-resistant strains was detected. The largest number of chromium-resistant strains was detected in the active sludge and aerotank, which is probably due to the recirculation of microorganisms in the wastewater treatment. The highest percentage of Cr (VI) resistant microorganisms was among sulphate-reducing bacteria. An increase in the percentage of chromium-resistant microorganisms occurred together with the lowering of the total number of microorganisms of a certain physiological group. These microorganisms could prove useful for the development of biotechnological methods wastewater treatment to eliminate chromium compounds, which are highly toxic to living organisms.

PERFORMANCE EVALUATION OF EXISTING WASTE WATER TREATMENT PLANT

Dairy industry is one of the major industries causi ng water pollution. In India, dairy industry genera tes about 6-10 L of wastewater/L of milk processed, depending upon the process schem e and products manufactured. Poorly treated wastewa ter with high levels of pollutants caused by poor design, operation or main tenance of treatment systems creates major environm ental problems, when such waste water is discharged to surface water or on la nd. Considering the above stated implications an at tempt has been to evaluate the performance of wastewater treatment plant (WWTP) at KMF dairy, Gulbarga. Samples were collected from s even points; Raw waste water [P1] to Secondary clarifier [P6] including th e treated effluent [P7] to evaluate the performance of WWTP. Parameters analyzed for evaluation of performance of WWTP are pH, Acidity, Alkalinity, COD, BOD 5 @ 20° C, TS. Tests were performed to find the fate of pollutants in WWTP. The present study sthat COD removal efficiency of WWTP was found to be 49.89% and BOD 5 removal efficiency of WWTP was found to be 74.07%. Though COD efficiency is high but its concentration in the treated effluent exceeds the limit prescribed by the regulatory auth orities. Hence it is recommended to redesign the WW TP to achieve better performance.

A Study on the Improvement of Membrane Separation and Optimal Coagulation by Using Effluent of Sewage Treatment Plant in Busan

The objectives of this paper are the characterization of the pretreatment of wastewater by microfiltration (MF) membranes for river maintenance and water recycling. This is done by investigation of the proper coagulation conditions, such as the types and doses of coagulants, mixing conditions (velocity gradients and mixing periods), pH, etc., using jar tests. The effluent water from a pore control fiber (PCF) filter located after the secondary clarifier at Kang-byeon Sewage Treatment Plant (K-STP) was used in these experiments. Two established coagulants, aluminum sulfate (Alum) and poly aluminum chloride (PAC), which are commonly used in sewage treatment plants to treat drinking water, were used in this research. The results indicate that the optimal coagulation velocity gradients (G) and agitation period (T) for both Alum and PAC were 200-250 <TEX>$s^{-1}$</TEX> and 5 min respectively, but the coagulation efficiencies for both Alum and PAC were lower at low values of G and T. For a 60 min filtration period on the MF, the flux efficiencies (<TEX>$J/J_0$</TEX> (%)) at the K-STP effluent that were coagulated by PAC and Alum were 92.9 % and 79.9 %, respectively, under the same coagulation conditions. It is concluded that an enhanced membrane process is possible by effective filtration of effluent at the K-STP using the coagulation-membrane separation process.

소규모하수처리시설의 이차침전조 내통길이 변화를 통한 탈수여액의 처리

The purpose of this study is to evaluate a de-watering filtrate treatment and the possibility of securing biological treatment capacity by changing the structure of the secondary clarifier. Accordingly, the column test was conducted to determine the effect of polymer in the de-watering filtrate on sludge sedimentation. Also, the characteristics of de-watering filtrate processing was evaluated through batch test and continuous processing operation. The results showed that sludge settling velocity increased with higher polymer concentration, and that effluent SS concentration was found to decrease. Regarding processing characteristics of de-watering filtrate, the removal efficiency of TSS and TBOD5 increased as the length of secondary clarifier was longer. Also, comparing injections into anoxic tank and secondary clarifier, de-watering filtrate by continuous infusion treatment process showed stability in both conditions. Therefore, by modifying the structure of secondary clarifier, efficient processing of de-watering filtrate is expected to be possible and processing capacity of small sewage treatment plants is considered to be improved.