Final Settling Tanks Research Articles

PERENCANAAN INSTALASI PENGOLAHAN AIR LIMBAH (IPAL) PABRIK TEMPE DENGAN DIGESTER ANAEROBIK DAN BIOFILTER ANAEROBIK DI WILAYAH SEMARANG (Studi Kasus Pabrik Tempe Dampyak Gunung Pati Kota Semarang)

The tempe industry is a food industry that has the potential to pollute the environment from the liquid waste it produces. Liquid waste from the tempe processing process if it is immediately disposed of without going through the management process first will have an impact on environmental pollution. In Semarang City, precisely in Gunung Pati District, there is a medium-scale tempe processing factory. So far, the tempe factory's liquid waste is directly disposed of into a ditch behind the factory without processing the liquid waste first.This research is a quantitative research presented in the form of numbers and then explained in the form of descriptions. From the results of the wastewater quality test, the pollutant parameters BOD = 369 mg/L; COD = 28,000 mg/L; TSS = 0.991 mg/L; and pH = 4,3. According to the Regional Regulation of the Province of Central Java Number 5 of 2012 concerning Amendments to the Regional Regulation of the Province of Central Java Number 10 of 2004 this value still does not meet the requirements. The wastewater treatment plant that the researchers are planning is in the form of a holding tank; Equalization Tub; Anaerobic Digesters; Gas Holder; Initial Settling Tub; Anaerobic Biofilter using bioball filter media and steel nets as a barrier for bioballs where bacteria are grown; and Final Settling Tank. With an estimated effluent from the processing of BOD, COD, and TSS of 7.47225 mg/L; 189mg/L; and 0.00669 mg/L which means it meets the quality standard. From the planning results, it was obtained that the total budget plan for planning the tempe factory wastewater treatment plant was Rp. 111.280.021,49.

Efektivitas Instalasi Pengolahan Air Limbah Berdasarkan Parameter COD, BOD, TSS, pH (Studi Kasus Industri Tahu di Dusun Janten Ngestiharjo Kasihan Bantul)

The liquid waste generated from tofu production process contains high Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solid (TSS) as well as low pH levels or acidity. Therefore, the tofu waste needs to be treated before being discharged into the environment to prevent negative impacts on the surrounding environment. Thus, this study aimed to test the effectiveness of the tofu wastewater treatment plant by monitoring the parameters of COD, BOD, TSS and pH using the closed reflux titrimetry, gravimetri and pH meter methods. The sampling was carried out with triple sampling (triplo) at each testing point, which were the equalization tank, anaerobic baffle reactor tank, anaerobic filter tank, and final settling tank. The sample testing was conducted at the "Balai Laboratorium Kesehatan dan Kalibrasi Yogyakarta". The results of the testing were used to determine the reduction in COD and the increase in pH between the wastewater treatment plant tanks, and then the effluent of the wastewater treatment plant was compared with the wastewater quality standards. The results of this study indicate that the average reduction of COD in the effluent is 94%, BOD is 93%, and TSS is 87%. Based on these findings, it can be concluded that the effluent from the wastewater treatment plant is not yet effective in meeting the wastewater quality standards. However, it is worth noting that the pH parameter meets the wastewater quality standards, with an increase of +1.38 compared to the influent pH level. Therefore, in terms of this parameter, the wastewater treatment plant can be considered effective in raising the pH.

Occurrence and Removal of Microplastic in Sewage Treatment Facilities in Chungcheongbuk-do

Microplastics from sewage and wastewater treatment facilities can be discharged into rivers and oceans, and the treatment facilities themselves can be a point source of microplastic pollution. The microplastic detection status and methods were compared in Miwon, Cheongju, Jecheon, and Chungju sewage treatment facilities in Chungcheongbuk-do. Samples were collected from the inlet, filtration facility, and discharge of Miwon Sewage Treatment Facility, a Porous Substrate Bioreactor (PSBR) construction corporation. Additionally, the inlet, first settling tank, final settling tank and outlet samples were taken from three sewage treatment facilities (Cheongju, Jecheon, and Chungju), which use bioreactor transformation processes. In the results, raw water showed a range of 232-1,510 pieces/L, and effluent water showed a range of 0.7-6.7 pieces/L. All four sewage treatment facilities showed high treatment efficiency of 98.5-99.9%. The treatment processes showed high removal efficiency in the order of CNR (97.0%) > PSBR (95.9%) > NPR (91.5%) > SMART3 (70.3%). As a study was conducted on only one sewage treatment facility for each process, additional research is necessary.

Performance evaluation of a full-scale upflow anaerobic sludge blanket reactor coupled with trickling filters for municipal wastewater treatment in a developing country

Poor wastewater management remains a critical health and environmental challenge in most developing countries in Sub-Saharan Africa due to the lack of adequate infrastructure for collection and treatment. This study evaluated the performance and methane production of a full-scale upflow anaerobic sludge blanket (UASB) reactor of capacity 18000 m3/d, with post-treatment unit: trickling filters followed by final settling tanks for municipal wastewater treatment in Ghana. Data was collected on operational conditions and physicochemical parameters of wastewater (influent and effluent) over a period of 35 weeks in 2021 (from January to August). The influent biochemical oxygen demand to chemical oxygen demand (BOD:COD) ratio was 0.58 ± 0.16, indicating the presence of highly biodegradable compounds in the sewage. Operational conditions for the UASB reactors were observed to be within the optimal range for anaerobic systems, with an applied organic loading rate of 1.30 ± 0.79 kgCOD/m3/d. Generally, Plant performance was satisfactory with carbon removal at 93% for COD and 98% for BOD. Biogas yield was 0.2 m3/kgCOD removed, culminating in an average biogas production rate of 831.6 ± 292.7 m3/d. Average methane composition was 64.7 ± 11.9% of the biogas output, whilst an estimated 35% of the methane generated remained dissolved in the UASB effluent. The UASB reactor presents an efficient technology that can be implemented in developing countries for effective and sustainable wastewater management.

Biological treatment of slaughterhouse wastewater using Up Flow Anaerobic Sludge Blanket (UASB) - anoxic-aerobic system

Slaughterhouse wastewater (SWW) is heavily polluted wastewater. It contains high concentration of organic matters, suspended solids, nitrogen, phosphorus, oil and grease. Discharging of SWW without a proper treatment may cause many problems for the sewage network and municipal treatment plants. Thus, this study aims to investigate the treatability of SWW using a new treatment method consists of: Up-flow anaerobic sludge blanket (UASB) reactor, Anaerobic Anoxic and Oxic (A2/O), and Virginia Initiative Plant Method (VIP). The integrated process consists of UASB reactor, anoxic tank, aeration tank (UASBAA), and final settling tank, respectively.The value of the mixed liquor suspended solids (MLSS),and return activated sludge (RAS) flows from the final settling tank to the anoxic tank were 300% and 100% of the SWW inflow respectively. During the research the influence of HRT values in UASB, anoxic tank, and the aeration tank has been investigated on the efficiencies of pollutants removal that exist in SWW. The experiments proved that the suggested method achieved high removal efficiency of COD, BOD5, TS, TDS, TSS, NH4+, PO43−, and NO3−, respectively: 97.31%, 96.91%, 57.61%, 47.91%, 96.3%, 73.11%, 83.61%, 93.01%, at HRTs value of 24 h for UASB reactor; 12 h for anoxic tank: 24 h for aeration tank, and 3 h for final settling tank. The treated wastewater could be reused it in washing processes in the slaughterhouse or for the irrigation of industrial crops.

Redesign of Anaerobic-Aerobic Biofilter for Domestic Wastewater Treatment Plant In Textile Industry

One of the textile industries in Pasuruan already has a Domestic Wastewater Treatment Plant (WWTP) with a capacity of 35 m3 /day. The treatment process combined physical, chemical, and biological processes using an anaerobic-aerobic biofilter. The domestic WWTP consists of a collection tank, equalization tank, anaerobic-aerobic biofilter tank, a filtration tank, and a chlorination tank. Existing conditions indicate that the domestic wastewater generated exceeds the capacity of the WWTP. Additional employees become one of the factors causing the increase in domestic wastewater discharge. Inadequate capacity has forced the company to bypass domestic waste into rivers. This biofilter was chosen because it could reduce high BOD values, have low operating costs, and operate efficiently. The anaerobic-aerobic biofilter reactor consists of a pre-settling tank, anaerobic tank, aerobic tank, and final settling tank. The evaluation results denoted that detention time in pre-settling, anaerobic, and settling units did not meet the design criteria. Thus, changing the design according to the design criteria. The redesign result of the anaerobic biofilter includes the pre-settling tank with a diameter of 2,5 m and a length of 3 m, an anaerobic tank with a diameter of 2,5 m and a length of 15 m, so that the total volume in the anaerobic reactor is 88.3 m3 . Then anaerobic bath with a diameter of 2,5 m and a length of 6 m and a final settling tank with a diameter of 2,5 m and a length of 1,5 m so that the total volume in the aerobic biofilter reactor is 36,7 m3 .

Risk assessment of a municipal extended aeration activated sludge treatment plant using physico-chemical and in vitro bioassay analyses

The present study involves physico-chemical profiling and toxicity assessment of wastewater and sludge samples collected from subsequent treatment stages of extended aeration activated sludge (EAAS) process based municipal wastewater treatment plant (WWTP). Wastewater samples were collected from inlet, aeration tank, final settling tank and outlet, while sludge samples were collected from sludge bed. All the samples were tested for their physico-chemical properties using titrimetry, multi elemental analysis and Gas chromatography and Mass spectrometry (GC–MS)(in scan and SIM (selective ion monitoring) modes). Toxicity testing was done using in vitro bioassays viz., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cytotoxicity, 7-ethoxyresorufin-O-deethylase (EROD) assay for dioxin-like behaviour and alkaline comet assay for genotoxicity, on human hepato-carcinoma HepG2 cell line. Post-treatment liquid samples showed 12 fold chemical oxygen demand (COD) reduction and met discharge standards for most of the tested parameters. However, detection of organic contaminants such as phenols, phthalates and polycyclic aromatic hydrocarbons (PAHs) and a correlated low toxicity reduction in liquid and sludge samples after treatment revealed the need for up-gradation of the existing testing and treatment technologies. • A multiplicity of organic contaminants detected in effluent and sludge. • 12 fold reduction in effluent chemical oxygen demand (COD) post-treatment. • Slight increase in toxicity of effluent and sludge observed after final clarifier stage. • Correlation observed in COD and the three bioassay results. • Combination of Physico-chemical and toxicity assessments more useful.

Pilot-scale study based on integrated fixed-film activated sludge process for cement industrial wastewater treatment

Due to the lack of freshwater resources in Egypt, cement wastewater treatment was performed to widen the range of the water used in irrigation to face the massive future water scarcity. In this study, integrated fixed-film activated sludge (IFAS) was used as a biological treatment method. A laboratory pilot was established as a simulation of the IFAS process. The scale-pilot consists of a primary sedimentation tank, an IFAS tank equipped with an air blower, and a final settling tank. Three experimental attempts were performed using 3 different bio-carriers. In the first trial, Luffa sponges were used as natural bio-carriers and polyurethane sponges (PU) as artificial bio-carriers in the second trial, in addition to a combination between Luffa and PU sponges as a hybrid bio-carrier in the third trial. After analyzing the physicochemical properties of wastewater at the national research center in Cairo, the removal efficiency of TSS (total suspended solids), COD (chemical oxygen demand) , BOD(biological oxygen demand), TN (total nitrogen), and TP (total phosphorous) was 94.5%, 87.8%, 90.8%, 75.9%, and 69.4%, respectively in case of using the combination between Luffa and PU sponges. It can be concluded that using IFAS process was effective for cement wastewater treatment and the effluent wastewater met the Egyptian code limitations for reuse in agriculture purposes.

Perencanaan Instalasi Pengolahan Limbah Cair Rumah Sakit Aliyah 3 Kota Kendari

The purpose of this study was to determine the amount of liquid waste discharge at the hospital. Data from the number of hospital patient beds is 54 beds, so the activities taking place in Aliyah Hospital 3 in Kendari city produces a maximum discharge of liquid waste of 3.78/day. The form and design of processing liquid waste which is a rectangle with anaerobic- aerobic bio filter treatment system. Liquid waste processing with anaerobic-aerobic bio filter process consists of several parts namely the oil separator tank, equalization tank, early settling tank, anaerobic bio filter tank, aerobic bio filter tank, final settling tank and equipped with a chlorinated contractor tub. As for the size of each tank, which is like an oil separator tank (0,9 m × 0,5 m × 0,7 m), equalization tank (2,6 m × 1,3 m × 1,1 m), early settling tank (1,6 m × 0,8 m × 0,9 m), anaerobic bio filter tank (2,5 m × 1,3 m × 1,4 m), aerobic bio filter tank (1,8 m × 1 m × 1 m), final settling tank (1,8 m × 0,7 m × 0,7 m) and chlorinated tank (0,6 m × 0,3 m × 0,4 m). This process system was chosen because it is in accordance with the amount of liquid waste treatment system is safe, inexpensive and easy to operate.

Perencanaan Desain Instalasi Pengolahan Air Limbah dengan Metode Biofilter Anaerob – Aerob

Planning design of wastewater treatment plant in a market is needed to improve the quality of water that will be discharged so it doesn’t pollute the environment and the near. The goal of this study is to determine the discharge of wastewater will be treated and the design of treatment basin in the wet lods area of Mandonga Traditional Market. Result of wastewater is 7.88 m3/day with a waste concentration of pH 7, BOD 64.2 mg/day, and TSS 2.130 mg/day. Wet Lods Wastewater Treatment Plant in Mandonga Traditional Market has 6 compartments such as a control tub with the fine filter addition which has a volume of 0.072 m3/day, the initial settling tank has a volume of 1 m3/day, anaerobic biofilter has a volume of 1.83 m3/day, aerobic tubs have a volume of 0.42 m3/day, the final settling tank I has a volume of 1.1 m3/day and the final settling tub II has a volume of 1.1 m3/day.

Perencanaan Instalasi Pengolahan Limbah Cair Rumah Sakit Aliyah 3 Kota Kendari

The purpose of this study was to determine the amount of liquid waste discharge at the hospital. Data from the number of hospital patient beds is 54 beds, so the activities taking place in Aliyah Hospital 3 in Kendari city produces a maximum discharge of liquid waste of 3.78/day. The form and design of processing liquid waste which is a rectangle with anaerobic- aerobic bio filter treatment system. Liquid waste processing with anaerobic-aerobic bio filter process consists of several parts namely the oil separator tank, equalization tank, early settling tank, anaerobic bio filter tank, aerobic bio filter tank, final settling tank and equipped with a chlorinated contractor tub. As for the size of each tank, which is like an oil separator tank (0,9 m × 0,5 m × 0,7 m), equalization tank (2,6 m × 1,3 m × 1,1 m), early settling tank (1,6 m × 0,8 m × 0,9 m), anaerobic bio filter tank (2,5 m × 1,3 m × 1,4 m), aerobic bio filter tank (1,8 m × 1 m × 1 m), final settling tank (1,8 m × 0,7 m × 0,7 m) and chlorinated tank (0,6 m × 0,3 m × 0,4 m). This process system was chosen because it is in accordance with the amount of liquid waste treatment system is safe, inexpensive and easy to operate.

Perencanaan Desain Instalasi Pengolahan Air Limbah dengan Metode Biofilter Anaerob – Aerob

Planning design of wastewater treatment plant in a market is needed to improve the quality of water that will be discharged so it doesn’t pollute the environment and the near. The goal of this study is to determine the discharge of wastewater will be treated and the design of treatment basin in the wet lods area of Mandonga Traditional Market. Result of wastewater is 7.88 m3/day with a waste concentration of pH 7, BOD 64.2 mg/day, and TSS 2.130 mg/day. Wet Lods Wastewater Treatment Plant in Mandonga Traditional Market has 6 compartments such as a control tub with the fine filter addition which has a volume of 0.072 m3/day, the initial settling tank has a volume of 1 m3/day, anaerobic biofilter has a volume of 1.83 m3/day, aerobic tubs have a volume of 0.42 m3/day, the final settling tank I has a volume of 1.1 m3/day and the final settling tub II has a volume of 1.1 m3/day.

Application of effective microorganisms technology on dairy wastewater treatment for irrigation purposes

Due to the massive amounts of freshwater consumed in dairy industries, as a result, thousands of liters of wastewater were produced as one liter of milk produces 10 liters of wastewater which represents a major threat to the surrounding environment and aquatic life. The application of a promising technology called “effective microorganism (EM)” was the key solution due to its low operating cost, low technology, and eco-friendly condition. Three different effective microorganisms were used, such as Bacillus bacteria (EM1), Staphylococcus bacteria (EM2), and EM stoste + Molasses (EM3). EM1 and EM2 were isolated from the dairy wastewater by using streaking for isolation on an agar plate process, while EM3 was prepared by mixing 12 % EM stoste, 6% molasses, and 82% distilled water. A laboratory pilot consists of aeration and final settling tanks, both tanks followed by an activated carbon filter. Four trials were performed, the first trial was without any EM, the second trial was adding EM1 with a dose of 50 ml to the aeration tank, the third trial was EM2 with a dose of 50 ml to the aeration tank, finally adding EM3 with a dose of 30 ml to the aeration tank. Results showed that using Bacillus bacteria (EM1) was the most effective trial as it was effective in reducing TSS (total suspended solids), BOD (biological oxygen demand), COD (chemical oxygen demand), TN (total nitrogen), and TP (total phosphorous) concentrations by removal efficiency of 93%, 96.2%, 95.9%, 94%, and 64%, respectively which were below the limitations of the Egyptian code for reuse for irrigation purposes.

Performance of Combined A/O Moving-Bed Biofilm Reactors for Biological Nutrients Removal from Domestic Wastewater under Different Gas/Water Ratios

In this experimental research, the continuous-upflow lab-scale combined A/O Moving-Bed Biofilm Reactors (MBBRs), with 50% A/O volume ratio and 100% internal NO3− recycling ratio, were constructed to treat 60 L/day of domestic wastewater in Basra Province (Southern Iraq) under full nitrification-denitrification processes. The A/O treatment system consists of Plexiglas square anoxic reactor with effective volume (15 litters), Plexiglas square aerobic reactor with effective volume (30 litters), and 250-litter Plexiglas square primary and final settling tanks. Cylindrical K1 plastic Kaldnes carriers with density of 0.93 g/cm3 were added to both reactors with 60% filling ratio to achieve the process of biofilm attaching. The A/O treatment system was operated under the batch mode for four weeks for development of biofilm; then the system was operated in continuous-upflow mode with total hydraulic retention time (HRT) equal to 18 hours and five different gas : water ratios (5 : 1,7 : 1,10 : 1,15 : 1, and 20 : 1) in order to investigate the effect of gas : water ratio on the total performance of A/O system. The study results illustrated that gas : water ratio has no effect on the removing of NH4+-N and COD, while it significantly affects the removing of TP and TN. The optimum value of gas : water ratio is 7 : 1, with the average value of removal efficiency (R%) of TP, TN, NH4+-N, and COD being 84.49%, 78.67%, 97.27%, and 95.56%, respectively. Under this value of gas : water ratio, the average values of dissolved oxygen (DO) in both aerobic MBBR and anoxic MBBR are 3.96 mg/L and 0.181 mg/L, respectively.

Improvement of Final Settling Tanks Performance by Using Chemical Additions

Biological treatment in wastewater treatment plants WWTPs consists of two main tanks, aeration tank and final settling tank. Aeration process using in return activated sludge system is very costly and it is required to operate WWTPs with low dissolved oxygen (DO) concentration in aeration process without risking poor effluent quality. To apply this study, a plant model for the addition of chemicals must be made with the necessary calibration of this model. Laboratory experiments were started between November 2017 and June 2018. This paper will discuss the impact of DO concentration on sludge properties by using a pilot plant model WWTP and find the optimum doses of Hydrogen peroxide H2O2 concentration with using low DO concentration to achieve good sedimentation. In this study the DO set-point was changed every 3 weeks between 0.5 mg/l and 4.5 mg/l for a few months. Experiments were carried out to The optimal ratio and dosage of H2O2 /Fe+2 was 5 as 30/6 mg/l. BOD, COD, TSS and VSS removal efficiency by using H2O2 /Fe+2 were 91%, 89% 90% & 89%, respectively with DO = 1.5 mg/l at an increased rates were 21.3%, 25.4%, 20% & 12.7%, respectively. Results of paper proves that the addition of optimum H2O2 will save 2 mg/l of DO concentration and providing a high cost of using electricity and mechanical equipment compared to the non-use of H2O2.

SBR 및 MBR 공정을 이용한 분뇨폐수에서의 질소제거 특성

There are two treatment processes that are currently applied to ships are the biological treatment process using the activated sludge and the electrochemical treatment. However, neither of them are able to remove both nitrogen and phosphorus due to their limited ability to remove organic matters, which are main causes of the red tide. This study was conducted to identify the characteristics of nitrogen removal factors from manure wastewater by replacing the final settling tank in SBR (Sequencing Batch Reactor) process and applying immersion type hollow fiber membrane. SBR process is known to have an advantage of the least land requirement in special environment such as in ship and the immersion type hollow fiber membrane is more stable in water quality change. As the result, the average in the cases of DO (Dissolved Oxygen) is 2.9(0. 6~3.9) mg/L which was determined to be the denitrifying microorganism activity in anaerobic conditions. The average in the cases of ORP (Oxidation Reduction Potential) is 98.4~237.3 mV which was determined to be the termination of nitrification since the inflection point was formed on the ORP curve due to decrease in the stirring treatment after the aeration, same as in the cases of DO. Little or no variation in the pH was determined to have positive effect on the nitrification. T-N (Total Nitrigen) removal efficiencies of the finally treated water were 71.4%, 72.3% and 66.5% in relatively average figures, thus was not a distinct prominence. In being applied in ships in the future, the operating conditions and structure improvements are deemed necessary since the MEPC (Marine Environment Protection Committee). 227(64) ship sewage nitrogen is less than the standard of 20 Qi/Qe mg/L or the removal rate of 70%.

Implementation of CFD modeling in the performance assessment and optimization of secondary clarifiers: the PVSC case study

The water industry and especially the wastewater treatment sector has come under steadily increasing pressure to optimize their existing and new facilities to meet their discharge limits and reduce overall cost. Gravity separation of solids, producing clarified overflow and thickened solids underflow has long been one of the principal separation processes used in treating secondary effluent. Final settling tanks (FSTs) are a central link in the treatment process and often times act as the limiting step to the maximum solids handling capacity when high throughput requirements need to be met. The Passaic Valley Sewerage Commission (PVSC) is interested in using a computational fluid dynamics (CFD) modeling approach to explore any further FST retrofit alternatives to sustain significantly higher plant influent flows, especially under wet weather conditions. In detail there is an interest in modifying and/or upgrading/optimizing the existing FSTs to handle flows in the range of 280-720 million gallons per day (MGD) (12.25-31.55 m(3)/s) in compliance with the plant's effluent discharge limits for total suspended solids (TSS). The CFD model development for this specific plant will be discussed, 2D and 3D simulation results will be presented and initial results of a sensitivity study between two FST effluent weir structure designs will be reviewed at a flow of 550 MGD (∼24 m(3)/s) and 1,800 mg/L MLSS (mixed liquor suspended solids). The latter will provide useful information in determining whether the existing retrofit of one of the FSTs would enable compliance under wet weather conditions and warrants further consideration for implementing it in the remaining FSTs.

Critical modeling parameters identified for 3D CFD modeling of rectangular final settling tanks for New York City wastewater treatment plants

New York City Environmental Protection is in the process of incorporating biological nitrogen removal (BNR) in its wastewater treatment plants (WWTPs) which entails operating the aeration tanks with higher levels of mixed liquor suspended solids (MLSS) than a conventional activated sludge process. The objective of this paper is to discuss two of the important parameters introduced in the 3D CFD model that has been developed by the City College of New York (CCNY) group: (a) the development of the 'discrete particle' measurement technique to carry out the fractionation of the solids in the final settling tank (FST) which has critical implications in the prediction of the effluent quality; and (b) the modification of the floc aggregation (K(A)) and floc break-up (K(B)) coefficients that are found in Parker's flocculation equation (Parker et al. 1970, 1971) used in the CFD model. The dependence of these parameters on the predictions of the CFD model will be illustrated with simulation results on one of the FSTs at the 26th Ward WWTP in Brooklyn, NY.

Development of a flocculation sub-model for a 3-D CFD model based on rectangular settling tanks

To assess performance and evaluate alternatives to improve the efficiency of rectangular Gould II type final settling tanks (FSTs), New York City Department of Environmental Protection and City College of NY developed a 3D computer model depicting the actual structural configuration of the tanks and the current and proposed hydraulic and solids loading rates. Fluent 6.3.26™ was the base platform for the computational fluid dynamics (CFD) model, for which sub-models of the SS settling characteristics, turbulence, flocculation and rheology were incorporated. This was supplemented by field and bench scale experiments to quantify the coefficients integral to the sub-models. The 3D model developed can be used to consider different baffle arrangements, sludge withdrawal mechanisms and loading alternatives to the FSTs. Flocculation in the front half of the rectangular tank especially in the region before and after the inlet baffle is one of the vital parameters that influences the capture efficiency of SS. Flocculation could be further improved by capturing medium and small size particles by creating an additional zone with an in-tank baffle. This was one of the methods that was adopted in optimizing the performance of the tank where the CCNY 3D CFD model was used to locate the in-tank baffle position. This paper describes the development of the flocculation sub-model and the relationship of the flocculation coefficients in the known Parker equation to the initial mixed liquor suspended solids (MLSS) concentration X0. A new modified equation is proposed removing the dependency of the breakup coefficient to the initial value of X0 based on preliminary data using normal and low concentration mixed liquor suspended solids values in flocculation experiments performed.

Enhancement of settling tank capacity using a new type of tube settler

The effectiveness of a newly developed lamellar settler was confirmed by onsite experiments. The device had inclined parallel plates arranged in a vertical direction in a settling tank. This vertical arrangement method enables many more plates to be set compared to the conventional horizontal arrangement. As an original and distinctive innovation, both the right and left edges of the plates were closed, for removing the clear water between the plates, The tube settler modules were installed in a final settling tank of a sewage treatment plant. Tests conducted over a 9 months period showed that the system operated successfully and under normal operation conditions, the new device could treat almost the same flow rate as that treated by a conventional tank, 5,000 m(3)/day. For storm water, the new tube settler was demonstrated to enhance the settling tank capacity by up to 3 times.