Reclamation Of Secondary Effluent Research Articles

Gravity-driven membrane system treating heavy metals-containing secondary effluent: Improved removal of heavy metals and mechanism

This study aimed at investigating the removal performance of the gravity-driven membrane (GDM) system in treating the heavy metals-containing secondary effluent, as well as evaluating the respective roles of Fe and Mn addition on the removal of heavy metals. GDM process with the formation of biocake layer exerted effective removals of Cr, Pb and Cd, with an average removal efficiency of 98%, 95% and 40%, respectively, however, after removing the biocake layer, the removal efficiencies of Cr, Pb and Cd reduced to 59%, 85% and 19%, respectively, indicating that the biocake layer played a fundamental role in removing heavy metals. With the assistance of Fe, the removal efficiency of heavy metals increased, and exhibited a positive response to the Fe dosage, due to the adsorption by the freshly generated iron oxides. On the contrary, the Mn involvement would result in the reduction of Cd removal due to the competitive adsorption of residual dissolved Mn2+ and Cd. Furthermore, the addition of a high dosage of Fe increased the diversity of eukaryotic communities and facilitated the elimination of heavy metals, however, the involvement of Mn would lead to a reduction in microbial diversity, resulting in a decrease of heavy metal removal efficiency. These findings are expected to develop new tactics to enhance heavy metal removal and promote widespread application of GDM technology in the fields of deep treatment of heavy metals-containing wastewater and reclamation of secondary effluent.

Pretreatment for the reclamation of rendering plant secondary effluent with NF/RO: UF flat sheet versus UF hollow fiber membranes

Rendering plants produce large amounts of wastewater that could be reused at the plant with adequate treatment. Membrane fouling is the main problem during the treatment of this type of wastewater by nanofiltration (NF) and reverse osmosis (RO). In order to reduce membrane fouling, the rendering plant secondary effluent was pretreated with two types of ultrafiltration (UF) membranes: MW as a flat sheet and ZW-1 as a hollow fiber membrane. The fouling on NF/RO flat sheet membranes (NF90, NF270, and XLE) was evaluated with the resistance-in-series model, while the fouling mechanisms were assessed with crossflow models. The UF, NF, and RO permeates were characterized to determine its suitability for reuse in the rendering plant. ZW-1 reduced the flux decline by 67.0% for NF270, 1.6% for NF90, and 38.0% for XLE; while MW reduced the flux decline by 72.4% for NF270, 50.1% for NF90, and 68.1% for XLE. The pretreatment with MW resulted in higher fouling reduction and a permeate that is appropriate for industrial reuse (washing purposes in the rendering plant). In terms of fouling resistance, NF270 and XLE membranes showed less fouling resistance during the treatment compared to NF90. The highest quality of permeate was obtained with XLE membrane, satisfying the water requirements for steam generation. The predominant fouling mechanisms for NF/RO were partial and complete pore blocking. The best combination for rendering plant secondary effluent reclamation was UF with MW membrane and RO with XLE membrane.

Biofiltration of feedwater to control organic fouling of low pressure membranes

ABSTRACTThe application of low pressure membrane (LPM) technology, i.e., ultrafiltration and microfiltration, for drinking water treatment and secondary effluent reclamation has increased rapidly over the past two decades. A major drawback in the use and operation of LPM processes is fouling due to the deposition of organic matter present in the feedwater on the membranes which leads to reduced water productivity necessitating membrane cleaning, process downtime and eventual membrane attrition. Pretreatment of feedwater using biological processes (particularly slow sand filtration and biological activated carbon) has been investigated as a simple and cost-effective means to control organic fouling of the membrane. In this paper, membrane fouling by the organic matter in drinking water and secondary effluent, the mechanisms of biological treatment systems, and the effectiveness of biological processes for fouling reduction are reviewed. It has been demonstrated that biological processes have great potential for controlling the organic fouling of membranes.

Removal of Crotamiton from Reverse Osmosis Concentrate by a TiO2/Zeolite Composite Sheet

Reverse osmosis (RO) concentrate from wastewater reuse facilities contains concentrated emerging pollutants, such as pharmaceuticals. In this research, a paper-like composite sheet consisting of titanium dioxide (TiO2) and zeolite was synthesized, and removal of the antipruritic agent crotamiton from RO concentrate was studied using the TiO2/zeolite composite sheet. The RO concentrate was obtained from a pilot-scale municipal secondary effluent reclamation plant. Effective immobilization of the two powders in the sheet made it easy to handle and to separate the photocatalyst and adsorbent from purified water. The TiO2/zeolite composite sheet showed excellent performance for crotamiton adsorption without obvious inhibition by other components in the RO concentrate. With ultraviolet irradiation, crotamiton was simultaneously removed through adsorption and photocatalysis. The photocatalytic decomposition of crotamiton in the RO concentrate was significantly inhibited by the water matrix at high initial crotamiton concentrations, whereas rapid decomposition was achieved at low initial crotamiton concentrations. The major degradation intermediates were also adsorbed by the composite sheet. This result provides a promising method of mitigating secondary pollution caused by the harmful intermediates produced during advanced oxidation processes. The cyclic use of the HSZ-385/P25 composite sheet indicated the feasibility of continuously removing crotamiton from RO concentrate.

Nanofiltration/Reverse Osmosis as Pretreatment Technique for Water Reuse: Ultrafiltration Versus Tertiary Membrane Reactor

The potential for nanofiltration (NF) and reverse osmosis (RO) in secondary effluent reclamation is noteworthy, but both processes require extensive pre‐treatment to prevent membrane fouling and promote system longevity. In this study, performance of direct ultrafiltration (UF) and tertiary membrane bioreactors (tMBRs) as feed pre‐treatments were assessed on a pilot scale. Both technologies achieved high organic matter removal (87 and 93% for UF and tMBR, respectively). Differences in efficiencies were related to suspended biomass in the tMBR, which enhanced degradation of the dissolved organic substances (<5 mg/L) and also stabilized process performance by minimizing residual fouling. Whichever pre‐treatment was applied, RO reached higher rejection coefficients and low fouling levels. Nevertheless, lower normalized flux (12%) was achieved when the UF effluent was fed due to high concentration of organic substances. Membrane autopsies by scanning electron microscopy with dispersive X‐ray and Fourier transform IR spectroscopy revealed that organic fouling appears to be predominant on both NF/RO membranes. The main organic foulants identified were polysaccharides and proteins. Inorganic foulants mainly consisted of calcium, phosphorus, and iron. Complete removal of pharmaceutical active compounds was observed for RO, while NF presented moderate retention coefficients (94, 85, 70, and 27% for atenolol, paraxanthine, caffeine and clofibric acid, respectively).

Construction and validation of a long-channel membrane test cell for representative monitoring of performance and characterization of fouling over the length of spiral-wound membrane modules

The authors thank the German Federal Ministry of Education and Research (BMBF) for the financial support of the project “Fouling minimized reclamation of secondary effluents with Reverse Osmosis” (ReSeRO) under grant no. 02WA1076. Further, several people have given time and efforts on discussion of the introduced topic and are thus thanked Mr. A. Lerch (Chair of Water Supply Engineering, TU Dresden, Germany) for stimulating suggestions during the construction of the LCMTC, Mrs. J. Bruckner, Mr. G. Orzechowski and Mr. D. Diersche (Chair of Water Supply Engineering, TU Dresden, Germany) for their help regarding analysis and support on the setup of the test rig, respectively, Mr. D. Kreutzmann and Mr. M. Meinel for discussions on material strength and tensions, Mr. J. Friedrich (Institute of Lightweight Engineering and Polymer Technology, TU Dresden) for the supply of the PMMA model calculation on material strength and Mr. S. Bucs (KAUST) for his help with the Rhodamine B experiment.

Micropollutants removal from retentates generated in ultrafiltration and nanofiltration treatments of municipal secondary effluents by means of coagulation, oxidation, and adsorption processes

One important disadvantage of using ultrafiltration (UF) and nanofiltration (NF) for reclamation of secondary effluents from municipal wastewater treatment plants (WWTPs) is the necessity to dispose of the UF and NF retentates. Different advanced treatments including coagulation (iron and alum), oxidation (chlorine, permanganate and ozone) and powdered activated carbon (PAC) adsorption were compared for their efficiencies in removing 11 selected micropollutants and effluent organic matter (EfOM) from UF and NF retentates generated in the filtration of secondary effluents. Ozone exhibited better micropollutants and UV254 removal efficiencies than chlorine and permanganate. Similar abatement of organics was observed when the same specific oxidant dose was applied to UF and NF retentates. Coagulation preferentially removed high molecular weight compounds, being ineffective for the elimination of most micropollutants. In general terms, iron coagulation was more efficient than alum, since iron achieved higher DOC and UV254 removal at lower molar doses. In addition, PAC was an effective method for removing micropollutants, especially hydrophobic and aromatic compounds. The hybrid coagulation/ozonation process improved micropollutants and EfOM (DOC and UV254) removal. A specific ozone dose of 1mgO3mgDOC−1 was able to almost completely remove selected micropollutants from the UF retentate. The final effluent, which is likely more biodegradable and less toxic, could be recirculated to biological treatment processes in the WWTP, avoiding the continuous discharge of non-biodegradable micropollutants through the WWTP effluents.

Fouling mechanisms and primary foulant constituents in reverse osmosis membrane reclamation of a petrochemical secondary effluent

In this study, fouling in the system of reverse osmosis (RO) fed with ultrafiltration prefiltered petrochemical secondary effluent was studied by using a laboratory-scale RO setup. With the micro-analysis of the fouling layer, the residual organic foulants were found to be the primarily responsible elements for the evolution of irreversible fouling. After characterization of the dissolved organic matter in the wastewater with gas chromatograph-mass spectrometer, it had been identified that aromatic compounds and hydrocarbon compounds were the major chemicals. With the help of Fourier transformed infrared spectra, the aromatics were detected to be the predominant organic foulants found on the membrane surface. According to results of electron-dispersive X-ray microanalysis spectrometry, metal cations such as Fe3+ and Mg2+ also contributed to irreversible fouling to some extent. This study identified that reducing adsorption of the organics on the membrane surface is a more effective way or method to control membrane fouling in the reclamation of the secondary effluent.

A review of membrane fouling in municipal secondary effluent reclamation

Reclamation of municipal secondary effluent for non-potable purposes is considered vital in alleviating the demand for existing limited water supplies while helping to protect remaining water sources from being polluted. In recent decades, reverse osmosis and nanofiltration membrane technologies have become increasingly attractive for reclamation of municipal secondary effluent because they are highly efficient, easy to operate, and economical. However, membrane fouling is a major obstacle in the development of membrane technology in municipal secondary effluent reclamation. This paper reviews three types of membrane fouling in municipal secondary effluent reclamation, namely, effluent organic matter (EfOM) membrane fouling, microbial membrane fouling, and inorganic membrane fouling, as well as their correlation. Membrane fouling by EfOM and microbes are found to be severe, and they are significantly correlated. Most previous studies conducted laboratory-scale experiments of membrane fouling with model organic matters and bacteria, but these model organic matters and bacteria might still be unrepresentative. More studies on membrane fouling in municipal secondary effluent reclamation with actual wastewater are essential.

Effects of Operational and Cleaning Practices on Membrane Fouling during the Reclamation of Secondary Effluent from a Wastewater Treatment Plant

Effects of Operational and Cleaning Practices on Membrane Fouling during the Reclamation of Secondary Effluent from a Wastewater Treatment Plant

Fouling minimised reclamation of secondary effluents with reverse osmosis (ReSeRO)

Fouling minimised reclamation of secondary effluents with reverse osmosis (ReSeRO)

Fouling minimised reclamation of secondary effluents with reverse osmosis (ReSeRO)

Abstract A group of researchers from Israel and Germany investigates fouling minimized reclamation of secondary effluent of municipal waste waters for unrestricted irrigation. Countries with increasing water scarcity including Israel are forced to use secondary or tertiary effluents for irrigation. The quality of the effluents can be increased to the levels of drinking water with multistage membrane process where low pressure membranes, mostly ultrafiltration (UF) are used as a pretreatment to reverse osmosis (RO). The minimisation of the organic and biofouling on UF and RO membranes is achieved by different pretreatments including biofiltration, coagulation and adsorption on powdered activated carbon. The pretreatment options are considered separately and in various combinations. The reduced fouling will also be achieved by modification of the membrane surface by the manufacturer. This study incorporates field and lab experiments, the latter are performed for a better understanding of biofouling-induced ...

Evaluation of sewage sludge production and utilization in Greece in the frame of integrated energy recovery

The objectives of this work were to provide an overview of municipal activated sludge units in Greece, to determine the sludge annual production rates and to examine potential for energy utilization of dewatered sludge. 37 wastewater treatment plants, serving a population equivalent of 1.6 million, located throughout Greece, were investigated during this study, in order to determine the sludge production rate after secondary and tertiary wastewater treatment processes. The average sludge production amount was estimated at 0.04 kg dry matter per capita per day, corresponding to an average wastewater production rate of 246 L per capita and day. Tertiary processes resulted to higher amounts of sludge production; nevertheless, such processes are often required aiming to the reclamation of secondary effluents with a high reuse and acceptability potential. Considering the disposal cost of produced sludge, energy utilization could be a promising alternative method for efficient sludge management. Utilization of the energy content of the sludge was examined by using three options, consisting in anaerobic digestion of dewatered sludge, incineration, and anaerobic digestion followed by residue incineration; it was found that excess energy production reached to high values in the case of combined anaerobic digestion and incineration, while single anaerobic digestion resulted to the lowest power production rates.

Relating organic fouling of reverse osmosis membranes to adsorption during the reclamation of secondary effluents containing methylene blue and rhodamine B

Dyes fouling of reverse osmosis (RO) membranes and its relation to adsorption had been investigated by using a crossflow RO filtration setup. Methylene blue (MB) and rhodamine B (RB) were used as model organic foulants. The calculated amount of the irreversible sorption was related to the irreversible flux decline. The characteristic fouling kinetics was accounted by Langmuir–Hinshelwood (L–H) kinetics model for initial fouling, with the fouling rate constant k = 0.0556 μm s −1 min −1 and k = 0.0181 μm s −1 min −1 for MB and RB fouling RO membrane CPA2, respectively. And the subsequent fouling was attributed to the growth of a dye cake. A remarkable correlation was obtained between the quantified irreversible sorption and irreversible flux decline under the solution chemistries investigated. In the presence of divalent cation, the extent of flux decline was related to the competition model.

Fouling behavior and foulant characteristics of reverse osmosis membranes for treated secondary effluent reclamation

Despite considerable research effort undertaken by the scientific community, membrane fouling is still a major technical hurdle that needs to be addressed to enhance the cost-effectiveness of operating reverse osmosis (RO) system for wastewater reclamation. In this study, fouling behaviors (i.e. the rate and extent of flux decline and fouling reversibility) of a laboratory-scale RO system fed with ultrafiltration (UF) prefiltered secondary effluent were studied at two operationally important permeate recovery levels. The associated fouling mechanisms were delineated with the aid of microscopic analysis of the fouling layer characteristics (i.e. composition, morphology and the fouled membrane surface properties). There was a remarkable correlation between the different fouling behaviors observed and the characteristics of fouling layers developed. Organic fouling by carbohydrates and protein-like matters was found to be primarily responsible for the flux loss observed at the first-stage RO with a recovery of 55%. More severe organic fouling together with inorganic precipitation of calcium phosphate and calcium carbonate which resulted in a more drastic and irreversible flux loss was observed at the second-stage RO with a higher recovery of 70%. The membrane fouling potential of effluent organic matter (EfOM) was found to increase greatly with increasing permeate recovery. When permeate recovery was increased to 75% which corresponds to a feed water concentration factor of 4, the fouling potential was increased to 10 times its original value. This study identified the need for more effective organic fouling control at the second-stage RO.

Impact of anti-scalant on fouling of reverse osmosis membranes in reclamation of secondary effluent

The objective of the study was to evaluate the impact of anti-scalant on fouling of reverse osmosis (RO) membranes in reclamation of secondary effluent which was produced by a conventional activated sludge process at Kranji Water Reclamation Plant with the capacity of 151,000 m3/d. The study was carried out using a RO pilot plant with the capacity of 2.4 m3/h. The RO plant was in 2:1 configuration and was operated at 75% recovery and at membrane flux of 17 l m(-2) h(-1). Pilot trials were conducted with and without anti-scalant. Compositions of feed and concentrate streams were analyzed and the pilot data were normalized. The results of the study showed that the plant operation was stable during the first few days after stopping dosage of anti-scalant but after 3-6 days of operation the membranes were fouled. The time lag effect of anti-scalant without dosage was not reported previously and could be potentially beneficial to save chemicals. The membrane fouling was more serious at the second stage due to the formation of calcium phosphate scale when the pilot plant was operated without anti-scalant. The flux of fouled membranes could be completely recovered after clean-in-place (CIP) with citric acid, indicating that scaling dominated the fouling of the RO membranes. These findings in the study could be applied to select an appropriate anti-scalant for prevention from formation of calcium phosphate scale in the RO operation.

Development of novel backwash cleaning technique for reverse osmosis in reclamation of secondary effluent

The objective of the study was to further develop a novel cleaning technique for reverse osmosis in reclamation of municipal secondary effluent. This technique is a new backwash method via direct osmosis (DO) by intermittent injection of the high salinity (HS) solution without stopping of high pressure pump and it is environment and membrane friendly technique. In the study, DO-HS trials were carried out with a UF-RO pilot system which was operated on site with the secondary treated effluent as the raw feed. Different operating conditions for DO-HS treatment in the actual process were investigated. It was found that the operation for implementation of the DO-HS cleaning technique developed was easy. For the first time, the actual profiles of HS concentration, DO backwash flow rate, brine flow rate and permeate pressure during DO-HS treatment have been demonstrated. It was observed that turbidity of the brine stream during DO-HS treatment at 3 NTU was 5 times higher than that before DO-HS treatment. The results from this study have confirmed the previous hypothesis with DO-HS treatment that there would be a strong driving force for DO backwash to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal plant operating conditions in terms of RO feed flow rate, HS concentration and HS injection time are ready for the DO-HS method to be adopted and validated in a long-term continuous plant operation.

Membrane Fouling in the Reclamation of Secondary Effluent with an Ozone-Membrane Hybrid System

The current research is a pilot scale study on membrane fouling in an ozone-ceramic membrane hybrid system, aiming at the reclamation of secondary effluent which contains abundant organic substances and bacteria. Compared with the microfiltration process with 30 mg O3/L feed, the microfiltration without ozone sustained for a longer period of time and produced greater filtrate volume, while all other conditions were kept constant. The results of size exclusive chromatography (SEC) show that the number of large molecules increases after ozonation; this part of organic molecules may contribute more to 0.1 µm membrane fouling. Other evidence proves that ozone brings about the lysis of bacteria. This may account for the increase in the number of large organic molecules after ozonation.

Secondary effluent reclamation: combination of pre-treatment and disinfection technologies

A study was carried out to evaluate the efficiency of secondary effluent additional treatment, using a combination of pre-treatments (ring filter, physico-chemical and infiltration-percolation) followed by disinfection methods (chlorine dioxide, peracetic acid and ultraviolet light). Three different indicator microorganisms were determined: E. coli, total coliforms and somatic bacteriophages. The results show better efficiency of physico-chemical and infiltration-percolation processes. Bacteriophages were eliminated to a lesser extent than bacterial indicators in all the treatment systems. Chlorine dioxide and peracetic acid seems to be more efficient in disinfection than ultraviolet light when a ring filter is the pre-treatment used. For the same doses and contact times, the efficiency of the disinfection methods is higher when the pre-treatment used is the physico-chemical or the infiltration-percolation system. The final effluent quality from the physico-chemical treatment train and the infiltration-percolation treatment train, followed by the disinfectants, achieves an E. coli content that allows the reuse in most of the uses described in the Spanish legislation for wastewater reuse.

The effect of coagulation on the toxicity and mutagenicity of reclaimed municipal effluents

The objectives of this work were the assessment of the effectiveness of coagulation on the reclamation of secondary effluents and the evaluation of the quality of reclaimed waters by the examination of their ecotoxic and mutagenic properties. Aluminum coagulants resulted in higher removal of organic content, than iron coagulant, reaching up to 40%; the removal of heavy metals, such as zinc and copper was enhanced by the addition of a low strength anionic flocculant. The toxicity of pre-concentrated samples to the bacteria Vibrio fischerii was related to the heavy metal content, especially zinc and copper, indicating the significance of the metals bioavailability and their potential interactive effects. The secondary effluents exhibited mutagenic effects on strain TA 98; these effects were increased during coagulation with ferric chloride (both in absence and presence of flocculant). However, the addition of aluminum coagulants resulted in a decrease of mutagenic potential of secondary effluents, due to the extended removal of organic matter.