Removal Efficiency Of Suspended Solids Research Articles

Polyvinylchloride Ultrafiltration Membranes Modified with Different SiO2 Particles and Their Antifouling Mechanism for Oil Extraction Wastewater

AbstractNovel low-cost and antifouling polyvinylchloride (PVC)–based membranes were fabricated with regular and hydrophilic nano-SiO2 particles as additives. The modified membranes exhibited significant improvements in mechanical properties, surface hydrophilicities, and antifouling performances in filtration of oil extraction wastewater. The addition of two types of nano-SiO2 particles increased the quantities of hydrophilic functional groups on the surface of the PVC membranes, which enhanced the resistance to adsorption of oily hydrophobic contaminants. Compared with the unmodified membrane, the membranes modified by regular and hydrophilic nano-SiO2 (at optimal addition of 1.5 g) presented more steady initial fluxes and higher flux recovery ratios in every filtration cycle. Meanwhile, both modified membranes exhibited high removal efficiencies of suspended solids (more than 98%) and oil components (up to 95%). These findings indicate that PVC membranes modified with two types of nano-SiO2 particles ha...

REDUCTION OF TOTAL SUSPENDED SOLIDS AND CHEMICAL OXYGEN DEMAND FROM PALM OIL MILL EFFLUENTS USING THE ELECTROCOAGULATION PROCESS

This study investigated the feasibility of electrocoagulation (EC) process on the treatment of palm oil mill effluent (POME). The effect of several parameters namely initial pH, current density, stirring speed and operating time on removal efficiency of total suspended solids (TSS) and chemical oxygen demand (COD) were investigated. The experiments were conducted batch wise using 400 mL of the POME per batch and pair of aluminum electrodes immersed in the reactor. At optimal initial pH value of 6, current density of 12 mA/cm(2), stirring speed of 100 rpm and operating time of 15 minutes, removal of 86% and 36.5% of TSS and COD was attained respectively. The EC treatment is found to be suitable as a preliminary treatment of POME.

Enhancement of Nutrient Removal in a Hybrid Constructed Wetland Utilizing an Electric Fan Air Blower with Renewable Energy of Solar and Wind Power

The sewage treatment efficiency of hybrid constructed wetlands (CWs) was evaluated under different ventilation methods. The removal efficiencies of biochemical oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP) in the vertical flow- (VF-) horizontal flow (HF) CWs using an electric fan air blower by the renewable energy of solar and wind power were higher than those by natural ventilation, excluding only suspended solids (SS). The TN treatment efficiency in the CW using the air blower especially increased rapidly by 16.6% in comparison with the CW employing natural ventilation, since the VF bed provided suitable conditions (aerobic) for nitrification to occur. The average removal efficiencies of BOD, SS, TN, and TP in the effluent were 98.8, 97.4, 58.0, and 48.3% in the CW using an electric fan air blower, respectively. The treatment performance of the CWs under different ventilation methods was assessed, showing TN in the CW using an electric fan air blower to be reduced by 57.5~58.6% for inlet TN loading, whereas reduction by 19.0~53.3% was observed in the CW with natural ventilation. Therefore, to increase the removal of nutrients in CWs, an improved ventilation system, providing ventilation via an electric fan air blower with the renewable energy, is recommended.

Effect of physical property of supporting media and variable hydraulic loading on hydraulic characteristics of advanced onsite wastewater treatment system

A laboratory-scale study was carried out to investigate the effects of physical properties of the supporting media and variable hydraulic shock loads on the hydraulic characteristics of an advanced onsite wastewater treatment system. The system consisted of two upflow anaerobic reactors (a septic tank and an anaerobic filter) accommodated within a single unit. The study was divided into three phases on the basis of three different supporting media (Aqwise carriers, corrugated ring and baked clay) used in the anaerobic filter. Hydraulic loadings were based on peak flow factor (PFF), varying from one to six, to simulate the actual conditions during onsite wastewater treatment. Hydraulic characteristics of the system were identified on the basis of residence time distribution analyses. The system showed a very good hydraulic efficiency, between 0.86 and 0.93, with the media of highest porosity at the hydraulic loading of PFF ≤ 4. At the higher hydraulic loading of PFF 6 also, an appreciable hydraulic efficiency of 0.74 was observed. The system also showed good chemical oxygen demand and total suspended solids removal efficiency of 80.5% and 82.3%, respectively at the higher hydraulic loading of PFF 6. Plug-flow dispersion model was found to be the most appropriate one to describe the mixing pattern of the system, with different supporting media at variable loading, during the tracer study.

Removal of bacterial indicators and pathogens from domestic wastewater by the multi-soil-layering (MSL) system

This paper presents the performance and behavior of a multi-soil-layering (MSL) system to remove fecal contamination bacteria indicators and pathogens from domestic wastewater. The experimental setup was performed using a laboratory-scale MSL system (depth 30 × width 36 × height 65 cm). The MSL system was composed of soil mixture blocks (SMB) arranged in a brick-like pattern and surrounded by permeable gravel layers (PL). The SMB comprised sandy soil, charcoal, sawdust and metal iron at a dry weight ratio of 7:1:1:1. The hydraulic loading rate was 200 L m−2 day−1. Bacteriological analyses comprised total bacterial count at 22 and 37°C, fecal coliforms, total coliforms, Escherichia coli, streptococci, intestinal enterococci and pathogenic bacteria: Clostridium sp., Staphylococcus sp., Pseudomonas sp. and Salmonella sp. The best removal efficiency was achieved for Staphylococcus sp. by 1.42 log unit, while the lowest removal efficiency was found for E. coli by 1.01 log unit. The mean removal efficiencies of total suspended solids (SS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorous (TP) were 93, 86, 81, 78 and 80%, respectively. Based on these results, the MSL system could efficiently remove organic matter, phosphorus and nitrogen. However, the performance to reduce bacterial indicators and pathogens was still moderate.

반응표면분석법을 이용한 터널폐수 응집-혼화 공정의 주요인자 영향 분석 및 최적화

A coagulation-flocculation (CF) process using aluminum sulfate as a coagulant was employed to treat highly suspended solids in tunnel wastewater. Response surface methodology (RSM) based on a Box-Behnken design was applied to evaluate the effects of three factors (coagulant dosage, pH and temperature) on total suspended solids (TSS) removal efficiency as well as to identify optimal values of those factors to maximize removal of TSS. Optimal conditions of coagulant dosage and pH for maximum TSS removal changed depending on the temperature (). As temperature increased, the amount of coagulant dosage and pH level decreased for maximum TSS removal efficiency during the CF process. Proper adjustment of optimal pH and coagulant dosage to accommodate temperature fluctuations can improve TSS removal performance of the CF process.

Experimental Design of Electrocoagulation and Magnetic Technology for Enhancing Suspended Solids Removal from Synthetic Wastewater

Design of experiments (DOE) is one of the statistical method that is used as a tool to enhance and improve experimental quality. The changes to the variables of a process or system is supposed to give the optimal result (response) and quite satisfactory. Experimental design can defined as a test or series of test series by varying the input variables (factors) of a process that can known to cause changes in output (response). This paper presents the results of experimental design of wastewater treatment by electrocoagulation (EC) technique. A combined magnet and electrocoagulation (EC) technology were designed to increase settling velocity and to enhance suspended solid removal efficiencies from wastewater samples. In this experiment, a synthetic wastewater samples were prepared by mixing 700 mg of the milk powder in one litre of water and treated by using an acidic buffer solution. The monopolar iron (Fe) plate anodes and cathodes were employed as electrodes. Direct current was varied in a range of between 0.5 and 1.1 A, and flowrate in a range of between 1.00 to 3.50 mL/s. One permanent magnets namely AlNiCo with a magnetic strength of 0.16T was used in this experiment. The results show that the magnetic field and the flowrate have major influences on suspended solids removal. The efficiency removals of suspended solids, turbidity and COD removal efficiencies at optimum conditions were found to be more than 85%, 95%, and 75%, respectively.

Erratum to: On-line evaluating the SS removals for chemical coagulation using digital image analysis and artificial neural networks

Chemical coagulation is one of the most important processes for industrial wastewater treatment plants to remove the suspended solids (SS), which depend significantly on particle characteristics. A digital image analysis system was set up in this study for the on-line measurements of particle characteristics, including particle size distribution, equivalent diameter, total area, total volume, and the fractal dimension in the both coagulation and flocculation periods in chemical coagulation. Two real industrial wastewaters, textile wastewater and landfill leachate, were used for conducting the coagulation and flocculation processes with different polyaluminum chloride dosages in a batch reactor. The artificial neural network (ANN) models were used to construct the correlations between the monitoring data acquired and the SS removal efficiencies. The experimental results indicated that the ANN models were able to precisely predict the SS removal efficiencies and effluent SS concentration after the chemical coagulation, with the correlation coefficient (R 2) of 0.96–0.97 for real landfill leachate and R 2 of 0.93–0.97 for real textile wastewater, which provided significant benefits for the control of chemical coagulation.

전기응고법을 이용한 오염 수 정화

수중에서 인, 질소의 함유농도는 부유고형물의 농도에 비례하여 증가하기 때문에 부유고형물의 제거는 유기물과 함께 질소, 인을 동시에 제거할 수 있다. 부유고형물은 수중에 미분체를 투입하면 투입된 미분체와 부유고형물 사이에는 반데르발스 힘과 같은 인력이 작용하여 응집이 형성되고 이 응집덩어리는 자성을 띠게 된다. 이와 같은 자성응집덩어리를 자력에 의해 형성된 자성 매트릭스에 직접 부착시켜 분리 제거함으로써 오수를 세정할 수 있다. 본 자료는 자성분리기술과 관련하여 오수 내의 부유고형물의 제거특성에 대한 것을 실험적으로 평가하고 부유물의 제거효율에 대하여 규명하고자 한다. A magnetic fluid separation technology was confirmed to be very effective to remove the suspended solids from contaminated water. We have surveyed on the effects of operating variables on the characteristics of suspended solids(SS) removal investigated through the test runs using magnetic powder. Magnetic flocculation here formed by adsorbing fine magnetites on the surface of suspended solid was observed. The strength of magnet was of significance in determining the SS removal efficiency.

Research on the Biomass and the Backwash Sludge of Biofilter

Biomass change and removal efficiencies of suspended solids (SS) along the process in the filter were investigated. As the normal operation of the biofilter process was often influenced by the blockage, the SS and the particle size of the backwash sludge along the process were also analysed, in order to find at which position the filter is easily blocked and what causes the blockage. The results showed that the bottom of upward flow biofilter had a higher removal efficiency of SS, with the removal rate of over 70%. The biomass and the height of the filter had an obvious regularity and the biomass increased as height of the filter increased, but the biomass at the lower middle of the filter decreased with the increasing height of the filter. At the same time, the SS and the particle size of the backwash sludge along the process in the filter also indicated the similar results.

On-line evaluating the SS removals for chemical coagulation using digital image analysis and artificial neural networks

Chemical coagulation is one of the most important processes for industrial wastewater treatment plants to remove the suspended solids (SS), which depend significantly on particle characteristics. A digital image analysis system was set up in this study for the on-line measurements of particle characteristics, including particle size distribution, equivalent diameter, total area, total volume, and the fractal dimension in the both coagulation and flocculation periods in chemical coagulation. Two real industrial wastewaters, textile wastewater and landfill leachate, were used for conducting the coagulation and flocculation processes with different polyaluminum chloride dosages in a batch reactor. The artificial neural network (ANN) models were used to construct the correlations between the monitoring data acquired and the SS removal efficiencies. The experimental results indicated that the ANN models were able to precisely predict the SS removal efficiencies and effluent SS concentration after the chemical coagulation, with the correlation coefficient (R 2) of 0.96–0.97 for real landfill leachate and R 2 of 0.93–0.97 for real textile wastewater, which provided significant benefits for the control of chemical coagulation.

Settling basin design in a constructed wetland using TSS removal efficiency and hydraulic retention time

Using total suspended solid (TSS) removal efficiency and hydraulic retention time (HRT) as design parameters a design guideline of a settling basin in a constructed wetland (CW) was suggested; as well as management of sediment and particle in the settling basin. The CW was designed to treat the piggery wastewater effluent from a wastewater treatment plant during dry days and stormwater runoff from the surrounding paved area during wet days. The first settling basin (FSB) in the CW was theoretically designed with a total storage volume (TSV) of 453m3 and HRT of 5.5hr. The amount of sediment and particles settled at the FSB was high due to the sedimentation and interception of plants in the CW. Dredging of sediments was performed when the retention rate at the FSB decreased to approximately 80%. Findings showed that the mean flow rate was 21.8m3/hr less than the designed flow rate of 82.8m3/hr indicating that the FSB was oversize and operated with longer HRT (20.7hr) compared to the design HRT. An empirical model to estimate the length of the settling basin in the CW was developed as a function of HRT and desired TSS removal efficiency. Using the minimum tolerable TSS removal efficiency of 30%, the length of the FSB was estimated to be 31.2m with 11.8hr HRT.

Effects of Co-current and Cross Flows on Circular Enhanced Gravity Plate Separator Efficiencies

This study compares the effects of flow on oil and suspended solids removal efficiencies in circular enhanced gravity plate separator equipped with coalescence medium. Coalescence medium acts to capture rising oil droplets and settling solid particles and assist in the coalescence of oil and coagulation of solid. The circular separator uses an upflow center-feed perforated-pipe distributor as the inlet. The co-current flow is achieved using 4 increasing sizes of frustum, whereas cross flow uses inclined coalescence plates running along the radius of the separator. The different arrangement gave the cross flow separator a higher coalescence plan area per operational volume, minimal and constant travelling distance for the oil droplets and particles, lower retention time, and higher operational flowrate. The cross flow separator exhibited 6.04% and 13.16% higher oil and total suspended solids removal efficiencies as compared to co-current flow.

Development of a down-flow hanging sponge reactor for the treatment of low strength sewage

The process performance of a down-flow hanging sponge (DHS) reactor for treating low strength sewage (biochemical oxygen demand (BOD) 20-50 mg/L) was investigated in Bangkok, Thailand. The hydraulic retention time (HRT) was set at 4 h during the start-up period and was reduced to 1.5 h in a stepwise manner. Throughout the 300-day operational period, the DHS reactor shows high performance with respect to the removal of total suspended solid (>90% total suspended solid removal efficiency). No clogging of sponge media was observed in response to the self-digestion phenomena of the biofilm. At a HRT of 1.5 h, the BOD removal efficiency was sufficiently high (about 85%). The pathogen Escherichia coli and other coliform bacteria were removed almost completely as well (removal was 99.4% and 98.1%, respectively). Regarding the retained sludge activity measurement, the nitrite oxidation rate was higher than the ammonium oxidation rate (0.031 and 0.022 gram of nitrogen per gram of volatile suspended solids per day, respectively). In the 300 days of operation, the amount of excess sludge production was negligible. Thus, no sludge treatment system is required. Introduction of the DHS system in developing countries is recommended because this system requires a relatively small area, and has low electricity consumption and operation costs.

Performance of inorganic coagulants in treatment of backwash waters from a brackish aquaculture recirculation system and digestibility of salty sludge

In this work two inorganic coagulants, FeCl3 and polymeric aluminum sulfate (PAS) were tested for treating backwash waters from a drumfilter of a brackish RAS with a salinity level of 17.0g/L. Their performances in terms of removal of total suspended solids (TSS), turbidity, total organic carbon (TOC), total phosphorus (TP) and reactive phosphorus (RP) were investigated. The results show that the removal efficiencies of total suspended solids (TSS), turbidity, total phosphorus (TP) and reactive phosphorus (RP) at the brackish conditions are higher than these in fresh condition with the same dosage of FeCl3 reported in literature. Moreover, dosing PAS caused a 9% decrease in biochemical oxygen demand (BOD5) of backwash waters, compared to that of the control group without adding PAS. The effects of FeCl3 and PAS as well as the effect of compatible solutes on biomethane potential (BMP) of the sludge from the RAS were examined. The results of BMP tests show that addition of glycine betaine (GB) 0.50g/L, trehalose (T) 0.50g/L and the combination 0.25gGB/L plus 0.25gT/L enhanced BMP of the sludge by 9.0%, 11.6% and 10.3%, respectively, compared with that of the control group without addition of compatible solutes. However, inorganic coagulants, FeCl3 and PAS, reduced BMP of the sludges from the sieve of the brackish RAS by 5.3% and 15.1%, respectively. Particularly, PAS (2.4gAl/L) significantly lessened BMP. Therefore, PAS may not be a proper coagulant for concentrating sludges if anaerobic digestion is going to be adopted as a sludge post treatment approach to achieve sludge reduction and energy recovery. However, FeCl3 may be a potential coagulant to further coagulate and flocculate backwash waters from marine RAS without substantially affecting the anaerobic digestibility of sludge produced by addition of FeCl3.

Coagulation of highly turbid suspensions using magnesium hydroxide: effects of slow mixing conditions.

Laboratory experiments were carried out to study the effects of slow mixing conditions on magnesium hydroxide floc size and strength and to determine the turbidity and total suspended solid (TSS) removal efficiencies during coagulation of highly turbid suspensions. A highly turbid kaolin clay suspension (1,213 ± 36 nephelometric turbidity units (NTU)) was alkalized to pH 10.5 using a 5 M NaOH solution; liquid bittern (LB) equivalent to 536 mg/L of Mg(2+) was added as a coagulant, and the suspension was then subjected to previously optimized fast mixing conditions of 100 rpm and 60 s. Slow mixing speed (20, 30, 40, and 50 rpm) and time (10, 20, and 30 min) were then varied, while the temperature was maintained at 20.7 ± 1 °C. The standard practice for coagulation-flocculation jar test ASTM D2035-13 (2013) was followed in all experiments. Relative floc size was monitored using an optical measuring device, photometric dispersion analyzer (PDA 2000). Larger and more shear resistant flocs were obtained at 20 rpm for both 20- and 30-min slow mixing times; however, given the shorter duration for the former, the 20-min slow mixing time was considered to be more energy efficient. For slow mixing camp number (Gt) values in the range of 8,400-90,000, it was found that the mixing speed affected floc size and strength more than the time. Higher-turbidity removal efficiencies were achieved at 20 and 30 rpm, while TSS removal efficiency was higher for the 50-rpm slow mixing speed. Extended slow mixing time of 30 min yielded better turbidity and TSS removal efficiencies at the slower speeds.

Performance evaluation and a sizing method for hydrodynamic separators treating urban stormwater runoff.

This study reports on 6 years of performance monitoring of stormwater hydrodynamic separators in Korean urban catchments. One hundred and thirty-seven storm events were monitored in four hydrodynamic separators of two different types from 2006 to 2012. Mean values of the event average removal efficiencies of total suspended solids (TSS) for the four hydrodynamic separators were 43.69, 8.54, 42.84, and 14.35% with corresponding mean values of the event average surface overflow rates of 28.62, 40.07, 16.02, and 38.81 m/h, respectively. The low TSS removal efficiency was due to the high instantaneous surface overflow rates frequently occurring throughout a storm event and the abundance of fine particle fractions in the inflow (median particle diameter <75 μm). The Weibull function was used to simulate particle size distribution (PSD) in the runoff and the simulated PSD functions were further applied to the discrete settling theory to develop curves of TSS removal efficiency, as a function of surface overflow rate and median particle size of the inflow. The developed curves should be useful in determining the design peak flow rate and the size of a hydrodynamic separator for a stated goal of TSS removal efficiency.

Ecohydraulic-driven real-time control of stormwater basins

Control of stormwater basins can be a competitive measure to improve the ecohydraulics of urban rivers by increasing the removal efficiency of particles and agglomerated contaminants like heavy metals and by decreasing hydraulic peak flows. In this paper, we present a simulation study that evaluates the potential of ecohydraulic-driven real-time control of stormwater basins to improve water quality and decrease hydraulic stress in the receiving water body. Nine different static and dynamic control scenarios were analysed based on a detailed hydraulic and quality model of an existing small urban catchment equipped with a stormwater basin at its outlet. Under dynamic control, an outlet valve was manipulated to increase retention time. The removal efficiency for suspended solids could be significantly increased by all control strategies and the hydraulic peaks were reduced by at least 50%. At the same time, overflow of the basin is avoided to prevent flooding. The developed dynamic control strategies proved to be advantageous as they provide significantly higher removal efficiency for suspended solids and a possible flexible adaptation to future demands. The findings of this study have been confirmed by field experiments.

MINIMIZATION OF CHEMICAL RISK BY USING RECOVERED ALUMINIUM FROM METALLURGICAL SLAG AS COAGULANT IN WASTEWATER TREATMENT

Secondary aluminium production inherently generates significant amounts of slag of variate composition and including dangerous compounds. Consequently, a care treatment of the resulted slag is imperatively necessary for preventing the environment pollution and for recovering valuable materials even if present in low amounts. The aluminium recovering procedure is based on a chemical and hydrometallurgical slag treatment, leading to the technical grade aluminium sulphate (AS), possible to be used for the chemical treatment of wastewaters, or for processing the resulted primary and secondary sludge from treatment plants. To check such a possibility, lab-scale tests have been performed by using the recovered AS from different sorts of slag coming from small or large metallurgical units of Romania. A municipal wastewater was separately treated with commercial AS and with recovered AS, the optimal dose and pH being established by mean of the standard Jar-test. The short time well mixing of wastewater allow a good dispersion of the added AS and micro-flocculation. The subsequent slow and longer mixing allows formation of large flocks easy to be separated by a gravitational method (sedimentation). The experimental results indicate no major differences in the removal efficiency of chemical oxygen demand (COD), phosphorous, and total suspended solids (TSS) between the used recovered vs. commercial AS. The recovered AS from metallurgical slag is proved as being a valuable coagulant, contributing to agglomeration of suspended solids and colloids, and to the adsorption of various dissolved chemicals or dyes from wastewaters.

Sludge reduction and performance analysis of a modified sludge reduction process

A modified sludge process reduction activated sludge (SPRAS) technology was developed by inserting a sludge process reduction (SPR) module, composed of an aeration tank and a settler, before the activated sludge system was proposed in this study. Compared with the anaerobic/anoxic/aerobic (AAO) process, the SPRAS resulted in a remarkable decrease in sludge production by 76.6%; sludge decay owing to lengthy solids retention time (about 121.5 d) could be the major cause. During the 217-day operation, the oxidation-reduction potential (ORP) (from 54 to -198 mV) and pH (from 7.8 to 5.0) at the bottom of the SPR settler gradually decreased, and low ORP and pH were in favor of sludge reduction in the SPRAS system. The insertion of the SPR module improved the removal efficiencies of suspended solids, chemical oxygen demand and ammonium nitrogen, and total nitrogen concentration in the effluent was reduced from 23.89 ± 4.82 to 14.16 ± 3.98 mg/L by 50% influent bypassing the SPR module. These results indicated that the SPRAS process could produce much less excess sludge and guarantee better effluent quality than the AAO process.