Membrane filtration for tertiary treatment of biologically treated effluents from the pulp and paper industry.

Discharge waters from activated sludge processes in the pulp and paper industry and from a municipal wastewater treatment plant were filtered with various nanofiltration (NF) and low pressure reverse osmosis (RO) membranes. The purpose was to study flux, retention, and permeate quality after membrane filtration by using a high shear (CR-250/2) filter. The suitability of the achieved permeates for reuse at the industrial site is also discussed. The NF permeate was practically free from colour and organic compounds but contained significant amount of inorganic compounds e.g. chloride ions, especially when a high amount of sulphate containing discharge waters were filtered, in which case a low pressure RO membrane was needed to successfully remove monovalent anions. Organic compounds were almost completely retained by NF and RO membranes and organic carbon in the permeate was less than 10 mg/dm3 on average. The achieved permeate can easily be reused in paper production. Nanofiltration has a significantly higher flux and also a lower fouling tendency than reverse osmosis but it passes through monovalent ions when there is a high sulphate concentration in the water. Therefore, RO might be needed in such cases to produce excellent process water.     

Reuse potential analysis on WWTP effluent of industrial parks in Taiwan.

This study examined the reuse potential of the effluents discharged from several unified wastewater treatment plants (WWTPs) of industrial parks in Taiwan, with designed capacity exceeding 10,000 CMD. Parameters were selected based on the relevant reuse purposes. The "potential recycling percentage", R of the WWTP effluent was defined as the maximal percentage of pure water extractable by the "ideal reverse osmosis module" while the RO retentate still met local effluent standards and required no treatment. The analytical results demonstrated that the WWTP effluents had potential for recycling. A pilot plant was installed in one of the WWTPs. The treatment process included a sand filter, an ultrafiltration unit (UF) and a reverse osmosis module (RO). Results of this study demonstrated that the production quantity and quality are stable and appropriate for various purposes, including both industrial and domestic applications.     

Monitoring of coagulation performance and determination of coagulant dosage using a pilot in-line filter.

A rapid method using the pilot in-line filter to detect any change in coagulation performance was a proposed in this study. This method attempted to detect a change in coagulant dosage and mixing intensity by evaluating the filtrate quality of the in-line filter, which took the rapidly mixed water. Since the response time of this method was less than 10 min, it could be valuable to monitor the coagulation performance. The in-line filter was found more useful without underdrain. The in-line filter was more sensitive to a change in filtrate quality without underdrain than with underdrain. A new method, which combines a jar test with the in-line filter, was proposed to determine the coagulant dosage. This method reflected the actual plant situation more accurately than a jar test.     

Comparison of SAR (sodium adsorption ratio) between RO and NF processes for the reclamation of secondary effluent.

Secondary effluent reclamation and reuse has been considered as an alternative for agricultural irrigation water. Whilst all constituents in the reclaimed wastewater could affect plant growth and soil characteristics, the most important parameters for agricultural irrigation are salinity and SAR (Sodium Adsorption Ratio). Salinity affects the availability of crop water and sodium causes clay soils to disperse. Membrane technologies, especially NF (Nano-Filtration) and RO (Reverse Osmosis), have played in a key role reclaiming the secondary effluent. RO can remove monovalent and divalent cations simultaneously. However NF processes reject preferably divalent cations and most monovalent ions are allowed to pass through the NF membranes. This could make them have different SAR values for both NF and RO processes. Therefore the primary objective of this study is to examine if the SAR values of the reclaimed water could be changed while they undergo NF and RO processes. The measured SAR values of the secondary effluent, NF permeate, and RO permeate were 1.78, 4.67, and 0.72 respectively. The SAR value after NF (4.67) increased to more than twice that of the feed solution, whereas the SAR of the RO permeate decreased to 0.72. In general, the higher SAR the water has, the greater risk the soils have. Although the SAR value after NF was within the safe range, this increased SAR value will affect permeability of soil, thus limiting the reclaimed wastewater use for as agricultural irrigation water. Consequently, when the NF system is used for the reclamation of the secondary effluent, SAR has to be examined first because potentially it tends to increase the SAR value.     

Tertiary filtration in small wastewater treatment plants.

Tertiary filtration can be proposed in small wastewater treatment plants with impact on protected water bodies. Rotating disk filters may be adopted, in respect to conventional sand filters, when low availability of space and low investment costs are the prevailing conditions. The overall objective of this research was to evaluate the filtration efficiency of rotating disk filters; to compare effectiveness with traditional sand filters; to analyse thoroughly the importance of particle size distribution in wastewater tertiary filtration. In the experimental activity, conventional wastewater quality parameters were investigated and particle size distribution (PSD) was characterized to discuss the filter effectiveness. The effect of design and operation parameters of tertiary filters were discussed related to particle removal curves derived from particles counts. Analysis of particle size distribution can be very useful to help comprehension of filtration processes, design of filtration treatments and to decide the best measures to improve filter performance.     

给水厂污泥脱水技术改造设计方案研究

针对以黄河水为原水的给水厂污泥进行了混凝及优选比阻调理试验,结果表明:当进行给水厂污泥脱水技术改造方案设计时,可以不经过混凝处理,直接利用电厂粉煤灰作为比阻调理剂。细粉煤灰的最佳投加率为20%,粗粉煤灰的最佳投加率为30%,使污泥比阻由1013数量级降至1010数量级,改善了污泥脱水性能,所得滤饼含水率仅为40%~50%,易于剥离,能耗低,所得滤液的色度、浊度、CODMn均达到可直接回用标准。当进行技改工程设计时,建议选用带式压滤机或板框压滤机,既适应粉煤灰调理剂,又可节约投资。     

Membrane bioreactor application in wastewater re-use from the effluent of Bali primary WWTP, northern Taiwan.

Two MBR pilot systems were constructed and tested in the Bali Primary WWTP. The pilot study shows that two MBR systems, i.e. the Green-MenBio system (MBR-1) and the Bio-MF system (MBR-2), can both fulfill the requirement of wastewater reclamation standard. The MBR-2 system is more economical compared with MBR-1 system. The cost of US dollars 0.10-0.16/m3 is estimated to reclaim the effluent of primary WWTP in Taiwan. The Bali Primary WWTP has the capacity of 1,320,000 cmd which is the biggest in Taiwan. The domestic wastewater of partial Taipei City and Taipei County are collected and transported to the Bali Primary WWTP. The effluent of the Bali Primary WWTP is then discharged into the ocean through two 3.8 m marine outfalls. The AO processes are installed in both MBR systems. More than 90% of the NH3-N can be removed through the AO and membrane processes. The outflow of the MBR systems (without RO) can reach the quality of COD <30 mg/l, BOD <10 mg/l, SS <5 mg/l, NH3-N <3 mg/L. The outflow of the MBR system is proposed to transport 40 km south to the Taoyuan County where four new industrial parks are to be constructed. Part of the reclaimed water is to be used on irrigation and another portion is to be sent to the industries after RO treatment.     

Removal of cyanobacterial metabolites through wastewater treatment plant filters

Wastewaters have the potential to proliferate excessive numbers of cyanobacteria due to high nutrient levels. This could translate to the production of metabolites, such as the saxitoxins, geosmin and 2-methylisoborneol (MIB), which can impair the quality of wastewater destined for re-use. Biological sand filtration was assessed for its ability to remove these metabolites from a wastewater. Results indicated that the sand filter was incapable of effectively removing the saxitoxins and in some instances, the effluent of the sand filter displayed greater toxicity than the influent. Conversely, the sand filter was able to effectively remove geosmin and MIB, with removal attributed to biodegradation. Granular activated carbon was employed as an alternative filter medium to remove the saxitoxins. Results showed similar removals to previous drinking water studies, where efficient removals were initially observed, followed by a decrease in the removal; a consequence of the presence of competing organics which reduced adsorption of the saxitoxins.     

Tertiary treatment of biologically treated piggery wastewater using vibratory shear-enhanced RO membrane.

This study presents a good example for the tertiary treatment of biologically treated piggery wastewater using vibratory shear enhanced RO membrane (VSEP RO). Through a simple process combination, utilizing Bioceramic SBR(BCS) and VSEP RO, at Gimhae plant livestock wastewater is treated excellently to meet the strict effluent standards. Application of RO membrane directly to the biologically treated effluent has been successful without any pretreatment to reduce high suspended solids. The combination of VESP UF followed by RO filtration processes produced a higher recovery rate in the 3-week pilot test.     

Low energy/cost desalination: low dose and low mean ion resident time in concentrate stream of electro-dialysis reversal

Species, dose, and mean ion resident time (MIRT(c)) in the concentrate of electro-dialysis reversal (EDR) desalination are analysed. In the classical EDR, dimensions, flow, and velocity of dilute and concentrate are equal; Langelier saturation index (LSI) and CaSO4 saturation are used to control the scaling and fouling processes in concentrate, as such LSI < + 2.16 for preventing CaCO3 from fouling and CaSO4 saturation level < 200 for averting CaSO4 from precipitation. If LSI is more than allowable limit, acid is added in concentrate to keep CaCO3 continuously dissolving; if CaSO4 saturation level in concentrate is more than the allowable limit, sodium hexametaphosphate (SHMP) is added in concentrate to maintain CaSO4 dissolving. EDR, however, was successfully modernised to operate with the higher water recovery rate (R) without any anti-scalant and without acid; this new EDR operated with LSI at 2.29 and CaSO4 saturation level 358.9% at lower dose and lower MIRT(c). Dose and MIRT(c) are proposed to address the controlling process. Monographs for the acids and SHMP requirements, and for the desalting cost including desalting power, membrane surface area, and chemicals usage, are developed. By lowering R and polar reversal interval, EDR can be operated at MIRT(c) < 130 min; at MIRT(c0 < 130 min, desalting cost/ energy can be minimised by eliminating chemicals requirement.     

Determination and occurrence of organic micropollutants in reverse osmosis treatment for advanced water reuse

The growing demand on water resources has increased the interest in wastewater reclamation for multiple end-use applications such as indirect and direct potable reuse. In these applications, the removal of organic micropollutants is of a greater concern than in conventional wastewater treatment. This article presents a collection of data of trace organic micropollutants in an urban wastewater treatment plant (WWTP) in North East Spain using reverse osmosis (RO) membrane treatment. The RO rejection values of the organic molecules studied with a wide range of solute size and hydrophobicity were determined. Several chromatographic methods monitoring different endocrine disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs) were used. Results indicated that secondary effluents from this Spanish WWTP contained most of the studied organic compounds indicating incomplete removal of organics in the conventional treatment of the plant. However, the rejection of most micropollutants was high for all three RO membrane types (low energy, high rejection, fouling resistant) tested. It was observed that some selected micropollutants were less efficiently removed (e.g. the small and polar and the more hydrophobic) and the molecular weight and membrane material influenced removal efficiencies.     

Sewage reuse for aquaculture after treatment in oxidation and duckweed pond.

The benefits of treating sewage by pond systems offer, through a simple and low-cost technology, social and commercial benefits, from the waste raw materials. The objective of this work was to demonstrate an effective treatment of the sewage by using natural treatment systems, and use of treated wastewater for aquaculture. The study was conducted for the sewage generated from the IIT Kharagpur campus. After characterization of the sewage, laboratory scale experiments were conducted for treatment using oxidation pond and duckweed pond. Survival and growth of fishes were observed in the experimental ponds using treated sewage. Based on the experimental results, full-scale treatment plant was designed to meet the aquaculture water quality. From the economics of the proposed full-scale plant, and utilization of the treated sewage for aquaculture, it is estimated that, the amount of Rs. 20,0000 can be generated every year. This amount recovered from the aquaculture will be more than the operating cost of the treatment plant, hence, making the operation of sewage treatment plant self sufficient. Use of a UASB reactor as the first stage treatment before sewage passes to the oxidation pond, can be a more attractive alternative because of less land requirement as compared to the oxidation pond alone, and additional land can be made available for aquaculture to increase revenue.     

Roughing filtration as an effective pre-treatment system for high turbidity water

Effective water treatment is the prime goal of every water treatment facility. Chakwal Water Treatment Plant in Pakistan has been treating high-turbidity surface water through crude coagulation, sedimentation and slow sand filtration since the early 1980s. The process has always been tedious in terms of high coagulant dosage, large volumes of sludge and short filter runs especially after wet spells. A laboratory-scale study was conducted to see if roughing filtration, as the pre-treatment process, would help in reducing coagulant dose and sludge volume and improving effluent quality. Results indicated that up-flow rouging filtration with media grades decreasing in the direction of flow could reduce wet weather raw water turbidity (by more than 90%) and coagulant dose. Overall, the plant could save over US $54,000 annually in terms of coagulant cost only. Longer filter runs, improved product water quality leading to lower chlorine dose requirement, would be additional benefits.     

净水厂生产排泥水处理工艺研究与设计

通过对净水厂生产排泥水的产生和水质特性进行分析,确定沉淀池排泥水和滤池反冲洗废水为净水厂排泥水的主要组成,结合设计干泥量的计算确定排泥水处理规模,在分析排泥水处理系统工艺流程布置特点的基础上对排泥水收集、调节、浓缩和脱水工艺进行分析,并对其中排水池、排泥池、浓缩池、平衡池、脱水工艺和场地布置的设计要点进行总结。     

反渗透工艺处理电厂循环冷却排污水

针对电厂循环冷却排污水浊度高 ,含盐量高的水质特点 ,采用反渗透工艺进行处理 ,出水含盐量小于 2 0mg/L ,满足锅炉预脱盐补充水的要求。介绍了反渗透工艺及其预处理工艺 ,并对该工艺处理成本和工程运行问题进行了分析     

Membrane Process Design for the Reduction of Wastewater Color of the Mazandaran Pulp-Paper Industry, Iran

The aim of this study is evaluate the use of membrane bioreactor for wastewater treatment Mazandaran pulp and paper Industry. The qualification of wastewater is case study and Characteristics of this industry wastewater were determined by different experiments such as: COD, BOD, Color, densitometry, viscometry and TG/DTA analyzer. Also, the color creating agents in the investigated wastewater was characterized. Then In this study, flux, retention, and permeate quality of various Nanofiltration and low-pressure reverse osmosis membranes were investigated at two temperatures and by using a low shear (DSS Labstak M20®) and a high shear (CR250/2) filter. The overall aim was to study the suitability of Nanofiltration in purification of the discharge water from external activated sludge processes in the pulp and paper industry for reuse in the paper manufacturing process and to compare the results to Nanofiltration of paper machine process waters. The discharge waters were nanofiltered at a higher flux than paper machine process waters. The permeate was almost free of color and organic compounds but contained significantly more inorganic compounds than the permeate from the filtration of process waters. To successfully remove monovalent anions and inorganic carbon from the discharge water a low-pressure reverse osmosis membrane such as the TFC ULP membrane is needed. With that membrane the permeate flux is lower than for Nanofiltration membranes but the permeate quality is significantly better when considering inorganic ions such as sodium, chloride, nitrate and inorganic carbon (bicarbonate). The permeate flux was two times higher in the high shear filter than in the low shear filter but the retentions were significantly lower. The result of this study: decrease pollutants parameter in Tajan Rivers that is effluent because attention to surface water quality has limited in Iran.     

Application of immersed MF (IMF) followed by reverse osmosis (RO) membrane for wastewater reclamation: A case study in Malaysia.

A pilot scale membrane plant was constructed and monitored in Shah Alam, Malaysia for municipal wastewater reclamation for industrial application purposes. The aim of this study was to verify its suitability under the local conditions and environmental constraints for secondary wastewater reclamation. Immersed-type crossflow microfiltration (IMF) was selected as the pretreatment step before reverse osmosis filtration. Secondary wastewater after chlorine contact tank was selected as feed water. The results indicated that the membrane system is capable of producing a filtrate meeting the requirements of both WHO drinking water standards and Malaysian Effluent Standard A. With the application of an automatic backwash process, IMF performed well in hydraulic performance with low fouling rate being achieved. The investigations showed also that chemical cleaning is still needed because of some irreversible fouling by microorganisms always remains. RO treatment with IMF pretreatment process was significantly applicable for wastewater reuse purposes and promised good hydraulic performance.     

Agricultural recycling of the by-product concentrate of livestock wastewater treatment plant processed with VSEP RO and bio-ceramic SBR.

One of the problems in a reverse osmosis process for livestock wastewater treatment is disposal of the by-product concentrate. The agricultural recycling of the concentrate is more cost saving than a further treatment. Application of the concentrate reduces the chemical fertilizer amendment. The agricultural recycling of the concentrate from the Kimhae livestock wastewater treatment plant, processed with the VSEP RO and bio-ceramic SBR, was studied. The concentrate includes non-biodegradable humic ubstance and residual inorganic ions (NH4+, NO3-, PO4(3-), K+, etc.). The contents of N, P and K were 1,650, 382 and 2,059 mg L(-1), respectively. The total acidity of humic acids extracted from the concentrate was 5.17 cmol(+) g(-1), composed of 2.38 cmol(+) g(-1) of carboxylic group and 2.79 cmol(+) g(-1) of phenolic hydroxyl group. Coliforms and E. coli were not detected in the concentrate. The yield of rice plant with the concentrate applied to it resulted in similar production to that with chemical fertilizer applied. The water extractable nitrate content of the concentrate-applied land did not exceed that of chemical fertilizer applied, at soil depths of 30 and 60 cm. The percolated amount of nitrate into the water table in arable land with the concentrate applied showed a similar level to that treated with the chemical fertilizer.     

Removal of contaminants and pathogens from secondary effluents using intermittent sand filters

Intermittent infiltration percolation of wastewater through unsaturated sand bed is an extensive treatment technique aimed at eliminating organic matter, oxidizing ammonium and removing pathogens. The main purpose of this study was to determine the depuration efficiencies of a sand filter to remove contaminants from secondary wastewater effluents. Elimination of pathogenic bacteria (total and faecal coliforms, streptococci) and their relationship with the filter depth were investigated. Results showed a high capacity of infiltration percolation process to treat secondary effluents. Total elimination of suspended solids was obtained. Mean removal rate of BOD(5) and COD was more than 97 and more than 81%, respectively. Other water quality parameters such as NH(4)-N, TKN and PO(4)-P showed significant reduction except NO(3)-N which increased significantly in the filtered water. Efficiency of pathogenic bacteria removal was shown to mainly depend on the filter depth. Average reductions of 2.35 log total coliforms, 2.47 log faecal coliforms and 2.11 log faecal streptococci were obtained. The experimental study has shown the influence of the temperature on the output purification of infiltration percolation process.     

Experiences of nitrogen and phosphorus removal in deep-bed filters at Henriksdal sewage works in Stockholm

Deep-bed down-flow two-media filters were used in pilot plant studies with filtration of secondary settled wastewater. FeSO₄ or FeCl₃ was applied as a precipitation agent, and NaAc·3H₂O was chosen as a carbon source when denitrification was desired. The concentration of PO₄-P in the filtrate from the pilot plant study never exceeded 0.05 mg PO₄-P/l when iron salts were dosed. The curves showing the concentration of P-tot and PO₄-P in the filtrate as a function of the quotient between the dosage of iron and the concentration of PO₄-P in the influent to the filter followed approximately an exponential relationship. The total nitrogen reduction over the filter bed increased from an average of 2.3 mg (NO₃+NO₂-N/l at the beginning of each experiment to an average of 4.3 mg (NO₃+NO₂)-N/l towards the end of the lest. When only secondary settled wastewater, suspended solids, primary settled wastewater, iron salts, or sodium acetate was added, at a hydraulic load of 10 m/h, the time before clogging became 100 h, 10 h, 10 – 15 h, 20 – 40 h, and 20 – 40 h, respectively. Almost the entire pressure drop was located on the surface of the filter bed and 0.25 metre down in the expanded clay layer.