Removal Efficiency Of SS Research Articles

Re-use of water treatment works sludge to enhance particulate pollutant removal from sewage

This paper attempted to study the feasibility of reusing water treatment works sludge (“alum sludge”) to improve particulate pollutant removal from sewage. The main issues focused upon were: (1) the appropriate dosage of the alum sludge, (2) the appropriate operating conditions, and (3) the possible mechanisms for enhancement by adding alum sludge. Actual alum sludge and sewage were applied to a series of jar tests conducted under various conditions. It has been found that both the SS and COD removal efficiencies could be improved by the addition of the alum sludge, which was mainly attributed to the removal of relatively fine particles with a size of 48–200 μm. The appropriate dosage of the alum sludge was determined to be 18–20 mg of Al/L. Increasing the mixing speed or reducing the floc size of the alum sludge enhanced the SS and COD removal and the dispersed alum sludge could remove particulate contaminants with smaller size than the raw sewage. ToF–SIMS evidence revealed that the aluminum species at the surface of the alum sludge were effectively utilized for improving the SS and COD removal. It was postulated that the sweep flocculation and/or the physical adsorption might play key roles in the enhancement of particulate pollutant removal from sewage.

Equalization characteristics of an upflow sludge blanket – aerated biofilter (USB-AF) system

Equalization characteristics of the upflow sludge blanket-aerated bio-filter (USB-AF) were investigated with the fluctuated raw domestic sewage. Recycle of nitrified effluent from AF to USB triggered the equalization characteristics of the sludge blanket on both soluble and particulate organic matter. Increment of EPS in sludge blanket by nitrate recycle was detected and removal of turbidity and particulates increased at higher recycle ratios by bio-flocculation. Increased TCOD removal in the USB was due to both denitrification of recycled nitrate and entrapment of the particulate organic matter in sludge blanket. Capture of both soluble and particulate organic matter increased sludge blanket layer in the USB, which improved the reactor performances and reduced the organic load on the subsequent AF. Overall TCOD and SS removal efficiencies were about 98% and 96%, respectively in the USB-AF system. Turbidity in the USB effluent was about 44, 20 and 5.5 NTU, at recycle ratios of 0, 100 and 200%, respectively. Particle counts in the range 2-4 microm in the USB effluent were higher than those in influent without nitrate recycle, while particle counts in the range of 0.5-15 microm in the USB effluent decreased 70% at recycle ratio of 200%. The major constituent of EPS extracted from anaerobic sludge was protein and total EPS increased from 109.1 to 165.7 mg/g-VSS with nitrate recycle of 100%. Removal efficiency and concentration of T-N in the UBS-AF effluent was over 70% and below 16 mg/L, respectively.

Treatment of swine wastewater using MLE process and membrane bio-reactor

The aim of this study was to develop the optimum integrated treatment system for slurry type swine wastewater through field testing. Although composting and liquid composting are the most desirable processes to treat swine wastewater, inadequate composting has been blamed as critical non-point source pollutants. In the area with limited crop land and grass land, the most feasible method to handle slurry type swine wastewater would be that the solids portion from the solids/liquid separation process is treated by composting and then the liquid portion is treated by a series of wastewater treatment processes, including physicochemical treatment system and biological nutrient removal systems such as the modified Ludzack Ettinger (MLE) process and MLE process coupled with a membrane, to satisfy the different effluent criteria. When using the appropriate solids/liquid separation system, the removal efficiency of SS, COD(Cr), and TKN was 92.4%, 73.6%, and 46.0%, respectively and the amount of bulking agent required for composting and organic loading rate for the following wastewater treatment system can be reduced by 94.8% and 84.7%, respectively. When treating the effluent from solids/liquid separation process by MLE process, the optimal volume fraction for denitrification was 20% of total reactor volume and the optimum ratio of F/M and F(N)/M were increased with increase of C/N ratio. Since the effluent quality of MLE process is not enough to discharge, the DAF process was operated with addition of FeCl3 and cationic polyelectrolyte. The effluent from the DAF process was treated in the MLE process coupled with a crossflow ultrafiltration membrane to satisfy more stringent effluent criteria. When external carbon source is added to keep 6.0 of C/N ratio, the efficiency of denitrification is best. The optimum linear velocity and transmembrane pressure for MBR process was 1.8 m/sec and 2.1 atm, respectively. By addition of external carbon source, nitrogen compounds, especially NOx-N, were considerably removed. And by addition of powdered activated carbon, the removal efficiency of COD(Cr) and COD(Mn) and the membrane flux were increased dramatically.

Application of chemical precipitation for piggery wastewater treatment

Several series of experiments were conducted to investigate the treatment of piggery wastewater using chemical precipitation (CP) where various types of coagulants such as aluminium sulfate (Al2(SO4)3), poly aluminium chloride (PAC), ferric chloride (FeCl3), ferric sulfate (Fe2(SO4)3), ferrous sulfate (FeSO4) and ferrous chloride (FeCl2) were used. Throughout the experiments, CP was found to achieve high removal efficiencies for organic compounds and nutrients (nitrogen and phosphorus) from the piggery wastewater. Experimental results showed the optimal doses of FeCl3, Fe2(SO4)3, FeCl2 and FeSO4 was 2.0 g/L, while 0.31 g/L and 2.5 g/L were the optimum dose for PAC and Al2(SO4)3, respectively. The pH range 4-5 resulted in the best performance to all coagulants except FeCl2 and FeSO4, whose optimum pH were more than 6. Percentage removal efficiencies for COD were in the ranges of 70-80%, 90-95% for SS, 80-90% for organic-N and TP. Those removal efficiencies were achieved within 5 min of operation. Three times of repetition in CP resulted in higher removal efficiencies for COD, SS and colour up to 74%, 99% and 94% respectively, in which Al2(SO4)3 was used as the coagulant. Removal efficiencies of various water quality parameters in a continuously operated reactor were similar to those of the batch experiments. Biodegradable ratios (BOD5/COD) increased up to 65% after the application of CP.

Treatment of agricultural wastewater in two experimental combined constructed wetland systems in a tropical climate

Two designs of experimental combined constructed wetland systems were constructed: vegetated (Scirpus grossus Linn) subsurface horizontal flow bed followed by a vegetated vertical flow bed and a vegetated vertical flow bed over an unvegetated horizontal flow sand bed. The systems were used to compare the nitrification/denitrification efficiency in a tropical climate which has temperatures above an average of 25 degrees C throughout the year. The effluent from a biogas digester of pig farm wastewater with TKN and COD concentrations of approximately 400 and 1,000 mg/L was fed every 4 hours intermittently. The effluent was recycled to the system with the ratio of 1:1 and the hydraulic loading rate was increased from 3 to 6 and 12 cm/d including recycled water. At higher hydraulic loading rates, nitrogen COD and BOD removal efficiencies were lower. The SS, TP and fecal coliform bacteria removal efficiencies were not clearly affected by the high hydraulic loading or the different layout of the system. Nitrogen uptake by plants was very low in relation to the nitrogen loading of the systems. In general, the removal efficiencies of both types were comparable but the system with a vertical flow over horizontal flow sand bed is more suitable for sites with limited land area, although its construction can be more difficult than the system with horizontal flow followed by a vertical flow bed.

Coarse media filtration - an alternative to settling in wastewater treatment

In this paper coarse media filtration has been analysed as an alternative to the traditional settling in primary, secondary and tertiary treatment of wastewater. Various filter media configurations were evaluated for enhanced primary filtration. It was found that a dual media configuration based on Kaldnes biofilm media (1 and K2modified) were most suitable when taking both separation efficiency as well as filter run time into consideration. SS removal efficiencies of around 75% were achieved in the dual Kaldnes primary filter at around 20 m/h without any chemical addition and around 85% at low dosage (1-2 mg/l) of a high MW cationic polymer FO4440SH. In the latter case COD was removed by around 70%. Further experiments were carried out on a multi-media Kaldnes-Filtralite-Sand (KFS) filter for enhanced primary treatment as well as for secondary filtration directly downstream of a high-rate moving bed biofilm reactor, resulting in an extremely compact secondary treatment process. The secondary KFS-filter gave SS-removal efficiencies around 90% (effluent SS < 15 mg/l) and filter run times of around 24 hrs at filtration rates of 10 m/h (sludge loading rates of around 1 kg/m2h) when a small dose (2 mg/l) of polymer was used. It is also demonstrated that the primary filter may also be utilised as a pre-denitrification reactor. A denitrification rate of 1.5 kg NO3-N(equiv.)/m3d was achieved when the filter was operated at a filtration rate of 5 m/h.

The PPL filtration treatment for highway runoff

The purpose of this research is to design a device which can treat highway runoff, especially runoff during initial rainfall with high pollution intensity, by connecting it with the draining grid sink of a drainage ditch on a highway, through which runoff flows. Porous polypropylene (PPL) particles were used as a treatment agent. The device treated highway runoff during initial rainfall by filtration and adsorption. It had a capacity to treat highway runoff in an area of 7.0 m x 20.0 m when rainfall intensity was up to 10 mm/hr. Two cases of rainfall intensity were set for the experiment: 5 and 10 mm/hr. The relationships between the efficiency of SS and COD removals and the rainfall intensity were investigated. Using artificial highway runoff with constant flow and SS concentration, results of 70% or more of SS removal with 5 mm/hr and 50% or more with 10 mm/hr were obtained. COD removal efficiency was about 90% of SS removal efficiency. This device was effective to remove non-point source pollutants in runoff on highways.

MICROBIAL AND COD REMOVAL IN A MUNICIPAL WASTEWATER TREATMENT PLANT USING COAGULATION FLOCCULATION PROCESS

ABSTRACT This study was designed to improve the removal efficiency of COD, SS, and microorganism at the S. Giovanni a Teduccio municipal wastewater treatment plant, Naples, Italy. The plant consists of screen, sand grinder, oil removal, coagulation, flocculation and sedimentation units, hypochlorite disinfection, mechanical dewatering, and thermal sludge conditioning. A series of Jar-test was conducted on twelve samples taken after screen using FeSO4 alone or together with Ca(OH)2 at 100 rpm rapid mixing for 1 min, 30 rpm for slow mixing for 20 min and 30 min for settling. 150 mg L−1 and 450 mg/L doses of FeSO4 were used at a pH interval in between 6 and 9. The removals of COD, TSS, Escherichia coli and total coliforms were measured ranging from 40 to 70%, 70 to 90%, 96 to 99% and 97 to 99%, respectively when FeSO4 was used alone at 150 mg L−1 and 450 mg L−1 doses and at pH 6, 7 and 8. Wastewater discharge standards could be safely obtained at 150 mg L−1 dose of FeSO4 with the use of 220 mg L−1 Ca(OH)2 at pH 8 in terms of COD and E. coli removals resulted in 65% and 98%, respectively, with less sludge production to be disposed. Additionally, none of influent and supernatant samples tested in this study was found to be acute toxic on 24 h-born Daphnia magna at 50% dilution.

Identifying an interfering factor on chemical oxygen demand (COD) determination in piggery wastewater and eliminating the factor by an indigenous Pseudomonas stutzeri strain.

This study attempted to demonstrate nitrite interference on chemical oxygen demand (COD) determination in piggery wastewater, and the capability of aerobic denitrification of the SU2 strain which is capable of promoting the efficiency of nitrogen and COD removal from piggery wastewater. This study was performed in a 17-litre reactor with a 30% packing ratio, with a ratio of immobilized SU2 cells to sludge of 100:1. The ratio of aeration to nonaeration was 4 : 1.5. Removal efficiency of COD was 86.8%. Removal efficiency of BOD and SS was higher than 90%, and removal efficiency of NH4+-N and TKN was almost 100%. NO2- -N interference is significant when its concentration in piggery wastewater exceeds 100 mg l-1. COD in piggery wastewater can be indirectly reduced following nitrite reduction by SU2 strain. Utilizing immobilized SU2 cells in coordination with an SBR system simultaneously reduces nitrite and COD concentrations.

Characteristics of Municipal Wastewater Treatment Using Non - Thermal Plasma in the Presence of Bromide Ion

Abstract – This study was carried out to find the possibility of the new physical and chemical municipal wastewater treatment such as denitrification of ammonia and degradation of organics by ionized gas in presence of bromide ion as a bench-scale reactor. Removal efficiencies of organics and SS were not related to bromide ion concentration but Removal efficiencies of organics and SS increased as the rate of influent gas flow were higher. With higher bromide ion concentration and lower influent gas flow rate, the higher removal efficiency of total nitrogen was obtained. Municipal wastewater treatment using non-thenna1 plasma in the presence of bromide ion could be considered as an effective method for the removal of organic matter and ammonia nitrogen.

Removal Efficiency of Three Cold-Climate Constructed Wetlands Treating Domestic Wastewater: Effects of Temperature, Seasons, Loading Rates and Input Concentrations

This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD&amp;gt; 75%), P (&amp;gt; 90%) and total and ammonia N (40-80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3-6 years of monitoring. Iron-rich sand from Bsh and Bs horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.

Removal efficiency of three cold-climate constructed wetlands treating domestic wastewater: Effects of temperature, seasons, loading rates and input concentrations

This paper outlines the influence of temperature, flow rate and input concentrations on the treatment efficiency of organic matter and nutrients in constructed wetlands (CWs). Three integrated 10 PE systems with horizontal subsurface flow (HSF) treating domestic wastewater are described. Particular attention is devoted to: (1) aerobic pre-treatment in vertical-flow filters, (2) filter media with high phosphorus (P) sorption capacity, and (3) the treatment efficiency during winters. Aerobic pre-treatment followed by CW units including P sorption media removed most organic matter (BOD> 75%), P (> 90%) and total and ammonia N (40–80%). P retention was relatively stable in wetland filters, both with lightweight aggregates and ferruginous sand during 3–6 years of monitoring. Iron-rich sand from Bsh and Bs, horizons of ferro-humic podzols was efficient for P sorption, but removal efficiencies of COD, TOC and SS were negative. The differences in efficiency between cold and warm periods were less than 10 percentage points for all parameters. It is anticipated that temperature effects are partially compensated by the large hydraulic retention time. The findings suggest that HSF systems do not require vegetation.

Optimised particle separation in the primary step of wastewater treatment

Since the pollutants in wastewater to such a large extent are associated with particles, enhanced particle separation in the primary step of wastewater treatment should be aimed at. Space restrictions demand pretreatment options will a small “foot-print”. In this paper it is shown that coagulation with metal salts is very efficient but leads to excessive sludge production. It is demonstrated how the use of cationic polymers may reduce the sludge production considerably without ruining the SS-removal efficiency and also how improved flocculation, either chemically, by the addition of flocculants or physically, by improvement of settling tank design, may lead to better particle separation as well as smaller “foot-print” of the plant. As an alternative to primary settling, primary filtration in coarse, floating filters are discussed as well.

Optimised particle separation in the primary step of wastewater treatment

Since the pollutants in wastewater to such a large extent are associated with particles, enhanced particle separation in the primary step of wastewater treatment should be aimed at. Space restrictions demand pretreatment options will a small “foot-print”. In this paper it is shown that coagulation with metal salts is very efficient but leads to excessive sludge production. It is demonstrated how the use of cationic polymers may reduce the sludge production considerably without ruining the SS-removal efficiency and also how improved flocculation, either chemically, by the addition of flocculants or physically, by improvement of settling tank design, may lead to better particle separation as well as smaller “foot-print” of the plant. As an alternative to primary settling, primary filtration in coarse, floating filters are discussed as well.

Treatment of domestic wastewater mixed with crushed garbage and garbage washing water by advanced gappei-shori johkaso

By using an advanced anaerobic filter-contact aeration Gappei-shori Johkaso (AFAJ), a small-scale wastewater unit used in Japan, experiments of the treatment of the wastewater mixed with domestic wastewater and disposer wastewater which came from washing water of crushed garbage by disposer were made. After the introduction of disposer wastewater into domestic wastewater, BOD, TN and SS loads increased to 1.7 times, 1.1 times and 1.7 times, respectively. Results showed that in the 5-person-use type AFAJ, no remarkable decrease appeared to the BOD and SS removal efficiencies after introduction of disposer wastewater into domestic wastewater, however, TN removal efficiency decreased significantly. As a result, effluent BOD and TN concentrations were much higher than 20 mg·l−1. On the other hand, the 7-person-use type AFAJ, whose volume was 35 % bigger than that of the 5-person-use type AFAJ, could treat the above wastewater to be less than 20, 10 and 20 mg·l−1, respectively. In addition, it was shown that not many changes took place in the kinds and occurrence frequencies of protozoa and metazoa after the addition of the disposer wastewater, which suggested that the addition of disposer wastewater had increased the BOD and SS loads while it did not lead to much change in the component of the domestic wastewater.

Treatment of domestic wastewater mixed with crushed garbage and garbage washing water by advanced Gappei-Shori Johkaso

By using an advanced anaerobic filter-contact aeration Gappei-shori Johkaso (AFAJ), a small-scale wastewater unit used in Japan, experiments of the treatment of the wastewater mixed with domestic wastewater and disposer wastewater which came from washing water of crushed garbage by disposer were made. After the introduction of disposer wastewater into domestic wastewater, BOD, TN and SS loads increased to 1.7 times, 1.1 times and 1.7 times, respectively. Results showed that in the 5-person-use type AFAJ, no remarkable decrease appeared to the BOD and SS removal efficiencies after introduction of disposer wastewater into domestic wastewater, however, TN removal efficiency decreased significantly. As a result, effluent BOD and TN concentrations were much higher than 20 mg·1-1. On the other hand, the 7-person-use type AFAJ, whose volume was 35 % bigger than that of the 5-person-use type AFAJ, could treat the above wastewater to be less than 20, 10 and 20 mg·1-1, respectively. In addition, it was shown that not many changes took place in the kinds and occurrence frequencies of protozoa and metazoa after the addition of the disposer wastewater, which suggested that the addition of disposer wastewater had increased the BOD and SS loads while it did not lead to much change in the component of the domestic wastewater.

Intensification of a Pond System by Fibrous Carriers

A study was carried out on the intensification of a pond system, consisting of an anaerobic pond, a facultative pond and a polishing pond, in Anda City, Heilongjiang Province, by fibrous carriers packed in the anaerobic pond, by means of which the performance of the pond system was remarkably improved with higher removal capacities and efficiencies for SS, BOD5, COD, TN, TP and bacteria, compared with the conventional system. The mechanism for the intensified effect was found to be ascribed to the increase of biomass in the form of biofilm attached to the surface of the fibrous carriers and more even distribution of the biomass in the pond. A mathematical model based on the complete mixed flow pattern was developed both for the intensified and conventional anaerobic pond, and the organic degradation rate constant value K in the former was found to be much greater than that in the latter. The microbial communities in both the ponds were also observed.

Comparative Studies on the Primary Treatment of Municipal Wastewater for Ocean Disposal

The objective of this study is to evaluate the effectiveness of primary treatment on municipal wastewater before it is discharged into the ocean. A series of filter papers of specified pore size was applied to measure the removal of organics and solids in wastewater through various primary treatment processes. For plain sedimentation, the removal of suspended solids was always less than 50% while COD and BOD removals were 23-41% and 15-27%, respectively. For chemical coagulation with the addition of poly aluminium chloride (PAC), 70% SS removal was obtained with a PAC dose of 30 mg/l. If polyelectrolyte is added (about 1 mg/l), the dosage of PAC can be reduced to around 10 mg/l to maintain the SS removal efficiency at the same level. For air flocculation treatment by preaeration followed by sedimentation, the most achievable removal of solids from wastewater of more than 80% was obtained at an aeration rate of 0.5-1.0 Nl air/l. In particular it is more effective for smaller solids than for larger solids in wastewater. On organic removal, about 15-40% removal in terms of COD or BOD was obtained by treating wastewater with either plain sedimentation or air flocculation and sedimentation processes. The efficiency of organic removal from wastewater increased to about 60% by utilizing chemical coagulation and sedimentation treatment. Based upon the characteristics of tested municipal wastewater, in order to maintain the SS removal at 65% or above as regulated, the treatment processes of chemical coagulation or air flocculation followed by sedimentation should be employed.

Performance of a New Equipment for Treating Domestic Wastewater

A fixed-bed aeration reactor system was developed for on-site and small-scale wastewater treatment. The reactor was packed with horizontal plates as support materials. There was no clarifier in the system. Three operational regimes were tested, which were a 6 hours total cycle, 8 hours total cycle and 12 hours total cycle. Experimental results showed the reactor can treat household wastewater efficiently. Removal efficiencies of BOD and SS were 88% for the BOD loading rate of 0.12 kg-BOD/m3·d or 5.2 g-BOD/m2·d. Effluent BOD and SS concentrations were means of 18 mg/l and 6 mg/l during the whole time operation. Suspended solids efficiently sedimented on the horizontal support plates in a short settling time. Equations were developed to predict BOD consumption and sludge production as a function of influent soluble BOD and suspended solids. Useful design and operating parameters are identified for future evaluations of the fixed bed aeration reactor.

Water Quality Improvement of Secondary Effluent by an Oxidation Pond with Subsequent Sand Filtration Treatment

A series of oxidation ponds and subsequent sand filtration experiments was performed to improve the water quality of secondary effluent containing organics and nutrients. The results show that the main reaction mechanism in the oxidation pond is the fixation of inorganic nutrients by algae. T-N and T-P concentrations in pond effluent decrease to 80 % and 77 % of influent respectively owing to the sedimentation of the particulate fraction. A sand filtration experiment on the pond effluent was conducted. At a filtration rate higher than 5 m/day, physical filtration mainly takes place, and clogging of the sand filter occurs within 1–3 days. However, at a rate lower than 1 m/day, the process of decomposition of deposits is also observed, and the run length becomes longer (&amp;gt; 20 days). The removal efficiency of SS is very high, ranging from 97 to 100 %. The total removal efficiency by an oxidation pond with sand filtration treatment is 24 to 37 % in T-N and 32 to 75 % in T-P. The most rational filtration rate for good performance seems to be 0.5 m/day because of its long run length. The effect of fish (Rhinogobius brunneus) on this treatment becomes obvious, prolonging the run length by 20 % or more due to feeding on the deposits.