Biologically Treated Sewage Effluent Research Articles

Comparison of Membrane-Based Treatment Methods for the Removal of Micro-Pollutants from Reclaimed Water

Dual membrane hybrid systems generally produce reclaimed water for non-potable uses by blending microfiltered biologically treated sewage effluent (BTSE) and reverse osmosis (RO) permeate. This reclaimed water is found to contain a significant amount of micro-pollutants, which possibly cause toxicity effects to aquatic organisms and plants when exposed to it. Therefore, removing such pollutants from the reclaimed water before reaching the community is highly emphasized nowadays. The currently used treatment of the RO treatment of microfiltered BTSE is energy intensive and not cost effective. This paper focuses on less costly and efficient membrane-based hybrid treatment systems such as the microfiltration-adsorption (MF-GAC) hybrid system, Nano filter (NF) and RO in the removal of micro-pollutants from the microfiltered BTSE. Both the MF-GAC hybrid system and NF (with NTR 729HF membrane) removed 70 to 95% of micropollutants from microfiltered BTSE. The removal depends on the hydrophobicity, charge, and size of the micropollutants. RO was excellent in removing more than 90% of pollutants, while MF was inefficient, as the latter primarily depends on the size exclusion mechanism. Based on the finding, it is suggested to treat only a portion of microfiltered BTSE through the MF-GAC or NF membrane before blending with RO permeate to enhance the removal of micro-pollutants from reclaimed water. The development of sustainable hybrid systems for the removal of all micropollutants of different chemical and physical properties is the key for the water reclamation.

Cleaning efficiency of the fouled forward osmosis membranes under different experimental conditions

Forward Osmosis (FO) has been attracting increasing attention due to the advantages that offers when compared to other desalination processes. In our previous study, influence of different parameters on the performance of diluting seawater through wastewater reuse was successfully investigated. In the FO and reverse osmosis (RO) hybrid process, FO membrane fouling is one of the critical issues. In this study influence of various operating conditions (DS concentration, FS pH, crossflow rates and pressure) on fouling behavior and cleaning efficiency were extensively evaluated. The synthetic wastewater (SWW) that simulates effluent organic matter and generally found in the biologically treated sewage effluent (BTSE) was used as FS.At higher FS pH the system attaints the maximum membrane-particle interaction by formations of the small aggregates that promote membrane fouling with lower cleaning efficiency. Different cross-flow rates showed a big influence on membrane fouling and cleaning behavior. By rising flow rate from 400 mL/min to 700 mL/min the generated shear forces cause less deposition and higher cleaning efficiency of the FO membrane. Membrane materials play an important role in membrane-particle interactions consequently on controlling membrane fouling and cleaning behavior in the FO process. Moreover, the elevated DS concentration boosts fouling of the FO membrane and diminishes cleaning efficiency.

Specific Anaerobic Fluidized Bed Bioreactors as Pretreatment to Microfiltration in Domestic Wastewater Treatment for Reuse

Practical use of an anaerobic granular activated carbon (GAC) fluidized bed bioreactor (FBBR) as pretreatment to microfiltration was experimentally verified. A nature starch based cationic flocculants (GF) was employed in this study for testifying its impact on the performance of GAC–FBBR. The GAC–FBBR with and without addition of GF was evaluated in terms of dissolved organic carbon (DOC) removal from biologically treated sewage effluent (BTSE). With only a daily addition of 200 mg GF to GAC– FBBR and a depth of GAC of 500 mm, the biomass of GAC increased from 1.5 g/L to 4.2 g/L within operation period of 30 days while the system resulted in 5% better DOC removal. The results indicate that the GAC–FBBR as pretreatment could effectively remove the dissolved organics and improve the critical flux. Compared with the critical flux of BTSE with submerged microfiltration (SMF) alone (20 L/m2.h), the pretreatment by GAC–FBBR successfully increased the critical flux to 30 L/m2.h. Moreover, the addition of GF into GAC–FBBR could help in raising the critical flux to 35 L/m2.h.

Use of nanofiltration and reverse osmosis in reclaiming micro-filtered biologically treated sewage effluent for irrigation

Micro-filtered, biologically treated sewage effluent (BTSE) generally has high sodium adsorption ratio (SAR) and sodium (Na) and chloride (Cl) concentrations. Therefore it cannot be directly used for irrigating sensitive crops. A study was conducted on a micro-filtered BTSE from a Sydney water treatment plant to determine whether the BTSE can be treated using nanofiltration (NF) and reverse osmosis (RO) to bring these risk parameters within safety limits. The study showed that using NF and RO alone could not produce the required ratio of SAR. Furthermore, NF alone did not remove the necessary levels of Na and Cl ions while RO did. However, blending equal proportions of NF permeate and RO permeate obtained from a two stages hybrid treatment system consisting of NF followed by RO resulted in a product quality suitable for irrigation in terms of the above mentioned risk factors. Utilizing NF prior to RO reduced the RO membrane fouling as well. Both NF and RO removed most of the pharmaceutical and personal care products from the feed water and this may subsequently protect soil and ground water from potential hazards.

Experimental evaluation of microfiltration–granular activated carbon (MF–GAC)/nano filter hybrid system in high quality water reuse

In order to achieve high quality water reuse, a dual membrane hybrid system (combining microfiltration–granular activated carbon (MF–GAC)) adsorption hybrid system followed by nanofiltration (NF)) was used. This system׳s performance was evaluated in terms of organic matter, pharmaceuticals and personal care products (PPCPs), and removal of inorganic matter. Biologically treated sewage effluent (BTSE) collected from a water reclamation plant in Sydney, Australia was used as the water source. The removal efficiency of dissolved organic carbon (DOC) of MF–GAC strongly depends on the dose of GAC and filtration flux. MF–GAC system effectively removed hydrophobic organics (45–80%) as well as hydrophilic organics (50–80%). The removal of various PPCPs ranged from 33% to 92%, and as expected, the amount of inorganic matter removed by the MF–GAC system was very small. Hence, the NF system, as a second membrane system, was employed to polish the effluent from the MF–GAC hybrid system. The NF system rejected most of DOC (>95%), sulfates (99%) and a substantial amount of calcium (70%), and magnesium (60%) from MF–GAC effluent. Further, more than 90% of PPCPs were removed by the NF system. Overall the dual membrane hybrid system proved to be very effective in removing organics, PPCPs and inorganic matter. The MF–GAC followed by NF results in high quality water reuse and this system can serve as an effective treatment option for water reuse schemes.

Effect of Phosphorous on the Properties of Titania Produced from Ti-Salt Flocculated Sludge in Water Treatment

In this study, the removal of phosphorous (P) using Ti-salt flocculation of biologically treated sewage effluent (BTSE) was investigated for a year. The pH, alkalinity and concentration of P, before and after Ti-salt flocculation, were measured and compared. The sludge of Ti-salt flocculation was incinerated at 600 degrees C to produce titania nanoparticles which found to be doped with P Titania nanoparticles were characterised and their photocatalytic activity under UV light irradiation were also tested. Results indicated that the removal of P, which exceeded 97% in average, was not affected by the pH and the alkalinity of BTSE. The concentration of P in titania had no effect on the characteristics of titania nanoparticles in different seasons. Titania nanoparticles exhibited superior properties in terms of BET surface area and photocatalytic activity.

Removal of effluent organic matter by purolite fluidised bed and submerged membrane hybrid system

In this study, Purolite® A500PS was used to remove effluent organic matter in a fluidised bed and submerged membrane hybrid system (SMHS). It was found that the fluidised bed purolite column can effectively remove 73% of dissolved organic compound (DOC) from synthetic biologically treated sewage effluent (BTSE). DOC removal can be reduced further, by up to 95% when the fluidised bed purolite column was combined with a treatment by granular activated carbon column. Purolite® A500PS was also used as an adsorbent in the SMHS. The results showed that critical flux of the SMHS depend on the purolite size. Critical fluxes of SMHS were 30 and 35 L/m2.h where 0.1 g/L of purolite of sizes below 150 µm and 150–300 µm were used respectively. The removal efficiency of natural organic matter from synthetic BTSE by SMHS was a function of purolite dose. The removal efficiency increased from less than 60% to more than 70% when the purolite dose increased from 0.05g/L to 0.1g/L.

Dissolved organic matter in biologically treated sewage effluent (BTSE): Characteristics and comparison

Dissolved organic matter (DOM) in sewage effluent and its transformation during pilot wastewater treatment processes (WWTPs) was characterized and compared using size exclusion chromatography (SEC) as well as other organic matter analytic methods. DOM in effluents from an artificial wastewater, a landfill leachate, a saline wastewater, and DOM collected from surface water were also tested for comparison. As for pilot WWTPs operating with the same actual wastewater feed, the DOM transformation was comparable: low MW (< 500 Da) and middle MW (> 5000 Da) organic materials decreased, while humic-like substances with MW of 650 Da, 1700 Da and 2000 Da and large MW organic materials (SMPs) with MW > 10,000 Da were aggregated. DOM in effluents from different sewage displayed their own characteristic SEC chromatograms. The properties of sewage effluent were influenced by the wastewater source, operation parameters and the inflow style of the biological treatment process. The only intensity difference in the SEC chromatogram was observed for effluents from WWTPs operating with the same actual wastewater feed.

Seasonal variation in the properties of titania photocatalysts produced from Ti-salt flocculated bioresource sludge

Ti-salt flocculation of biologically treated sewage effluent (BTSE) was carried out on monthly basis during one year to trace the seasonal variation in the properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts. Titania photocatalysts were produced from incineration of Ti-salt flocculated sludge at 600 °C. The physio-chemical properties of BTSE, Ti-salt flocculated BTSE and titania photocatalysts were investigated. The photocatalytic activity of titania was examined using different substrates of rhodamine B and humic acid under UV light irradiation. Results indicated that the flocculation performance of Ti-salt was not affected by the seasonal variation of BTSE. BTSE characteristics resulted in marginal effect in titania characterisation and photocatalytic activity. Titania photocatalysts produced from Ti-salt flocculated sludge in different seasons showed constant anatase phase, high BET surface area and high photocatalytic activity.

Hydrogen production affected by Pt concentration on TiO2 produced from the incineration of dye wastewater flocculated sludge using titanium tetrachloride

TiO2 from the incineration of dye wastewater flocculated sludge using TiCl4 coagulant was produced. Optimal catalyst amount and Pt-loading on TiO2 were studied for the production of H2 by photocatalytic reforming of methanol (6% vol.). On the other hand, BTSE (biologically treated sewage effluent) was flocculated using TiCl4 and produced sludge was incinerated to generate TiO2. TiO2 was loaded with optimum Pt and added to the supernatant in a photocatalytic reactor to test the efficiency of using remaining organics as a “sacrificial reagent” for photocatalytic hydrogen production. Dissolved organic carbon (DOC) and molecular weight distribution (MWD) were measured for nanofiltration (NF) and TiCl4 flocculation followed by photocatalysis. TiO2 (from the incineration of BTSE flocculated sludge using TiCl4) was produced and loaded with 0.5% Pt. Results showed that the optimum concentration of TiO2 (from dye wastewater) for H2 production was 0.3 g/L, while the optimum amount of Pt was 0.5%. DOC and MWD removal was similar for the flocculation of BTSE followed by photocatalytic reaction and the NF process. Remaining organic compounds after flocculation could not be used as sacrificial reagent to induce H2 production. Further investigations on studying the UV intensity and/or identifying organic/inorganic scavengers to inhibit H2 production are underway.

Adsorption and bioadsorption of granular activated carbon (GAC) for dissolved organic carbon (DOC) removal in wastewater

In this study, the performances of GAC adsorption and GAC bioadsorption in terms of dissolved organic carbon (DOC) removal were investigated with synthetic biologically treated sewage effluent (BTSE), synthetic primary treated sewage effluent (PTSE), real BTSE and real PTSE. The main aims of this study are to verify and compare the efficiency of DOC removal by GAC (adsorption) and acclimatized GAC (bioadsorption). The results indicated that the performance of bioadsorption was significantly better than that of adsorption in all cases, showing the practical use of biological granular activated carbon (BGAC) in filtration process. The most significance was observed at a real PTSE with a GAC dose of 5 g/L, having 54% and 96% of DOC removal by adsorption and bioadsorption, respectively. In addition, it was found that GAC adsorption equilibrium was successfully predicted by a hybrid Langmuir–Freundlich model whilst integrated linear driving force approximation (LDFA) + hybrid isotherm model could describe well the adsorption kinetics. Both adsorption isotherm and kinetic coefficients determined by these models will be useful to model the adsorption/bioadsorption process in DOC removal of BGAC filtration system.

Performance of Granular Activated Carbon (GAC) Adsorption and Biofiltration in the Treatment of Biologically Treated Sewage Effluent

In this study, the performance of GAC adsorption and biofiltration systems in treating biological treated sewage effluent (BTSE) was evaluated in terms of organic removal efficiency, organic fractions, and molecular weight distribution (MW) of organic matter (OM) removed. The GAC biofilter removed 23.5% and 61% of the hydrophobic fractions and hydrophilic fractions of OM in the BTSE respectively. MW distribution studies of GAC filter and GAC adsorption revealed the following: Hydrophobic fraction of the effluent showed a peak at 345 dalton after GAC biofiltration and 256 dalton after GAC adsorption, whereas, with hydrophilic fractions, peaks at 46,178 and 345 daltons were observed after GAC biofiltration and peaks at 46,178 and 256 daltons after GAC adsorption. Transphilic fraction showed the peaks at 12,783 dalton with GAC biofiltration, and 1,463 dalton with GAC adsorption. The performance of the GAC biofilter was successfully mathematically modelled.

Application of hybrid photocatalysis systems coupled with flocculation and adsorption to biologically treated sewage effluent for organic removal

The application of a photocatalysis hybrid system coupled with flocculation and adsorption in treating biologically treated sewage effluent (BTSE) was investigated. The removal of organic matter was studied in terms of dissolved organic matter (DOC), removal of hydrophobic (HP), transphilic (TP) and hydrophilic (HL) fractions, and molecular weight (MW) distribution. The photooxidation removed the majority of MW (263, 580, 865, and 43109 daltons) within the first 30 minutes of operation. The removal of MW range of organic matter of 330 daltons was low. DOC removal of HP and TP was high (80%). DOC removal from HL fraction was, however, minimum. The photocatalytic system with simultaneous PAC adsorption and FeCl3 flocculation removed the effluent organic matter (EfOM) up to 90%. Therefore, photocatalysis with the ferric chloride (FeCl3) flocculation and PAC adsorption hybrid system can be a possible option in the removal of DOC from BTSE for water reuse.

Fouling of ultrafiltration membrane by effluent organic matter: A detailed characterization using different organic fractions in wastewater

Membrane fouling caused by hydrophobic (HP), transphilic (TP), and hydrophilic (HL) fractions in biologically treated sewage effluent (BTSE) are still not well understood. Some researches reported that the HP fraction (humic substances) were the major problem; other studies indicated that the HL fraction (polysacchrides) were the main causes for severe fouling in membrane filtration. Hence, in this study, a detailed ultrafilter experiments were conducted with the HP, TP, and HL fractions to study the membrane fouling. The ultrafiltration (UF) removed 67.4%, 52.9%, and 19.7% of HP, TP, and HL fractions, respectively. High removal of the HP fraction is due to relatively high MW of organic matter in the HP fraction and the interaction between the HP fraction and membrane surface. The flux decline with the HP fraction was high compared with the TP and HL fractions. The membrane fouled with different fractions was characterized in terms of functional groups, zeta potential, foulant concentration, and contact angle.

Foulant characterization of the NF membranes with and without pretreatment of biologically treated wastewater

In this study, different pretreatment methods such as ferric chloride (FeCl3) flocculation and powdered activated carbon (PAC) adsorption were evaluated in terms of their capability in removing effluent organic matter (EfOM) and the characteristics of the foulants on the NF membranes. A detailed experiment was conducted with two NF membranes (NTR 729HF with MWCO 700 daltons and LF 10 with MWCO 200 daltons). With pretreatment, the concentration of organic matter on the membranes decreased to 5.671 x 10(-3) (NTR 729HF) and 4.940 x 10(-3) (LF 10) mg EfOM/cm2 of membrane from 6.372 x 10(-3) (NTR 729HF) and 4.979 x 10(-3) (LF 10) mg EfOM/cm2 of membrane. The MW of the solute fraction of biologically treated sewage effluent (BTSE) ranged from 250 daltons to about 3573 (the most important being 250-520 daltons). The weight-averaged MW values of the foulants on the NTR 729HF membrane reduced from 304 daltons without pre-treatment to 208 daltons with pretreatment. In the case of EfOM, the small molecules (MW 300 to 500 daltons) are mainly responsible for the membrane fouling. Thus, the MW distribution of organic matter in the effluent and in the foulant can be used as a representative tool to evaluate the efficiency of pretreatment and NF and in the selection of their operating conditions.

Effect of pretreatment on the fouling of membranes: application in biologically treated sewage effluent

Reuse of wastewater can help in maintaining environmental quality and relieving the unrelenting pressure on conventional and natural freshwater sources. Membrane processes find an important place in the wastewater treatment for reuse. Nonetheless, reverse osmosis (RO) and nanofiltration (NF), i.e. non-porous membranes require higher operational costs and energy. Thus, in this research NTR 7410 ultrafiltration (UF) membrane which is porous was used without and with pretreatment to treat biologically treated sewage effluent (BTSE). Four different pretreatment methods, namely, ferric chloride (FeCl 3) flocculation, powdered activated carbon (PAC) adsorption, flocculation followed by adsorption, and granular activated carbon (GAC) biofilter were used in this study to compare their relative merits. Experimental results indicate that the most suitable pretreatment was flocculation followed by adsorption leading to a total organic carbon (TOC) removal of 90%. To assess the suitability of the membranes, it is important to conduct a detailed membrane characterization. The fouled NTR 7410 membrane surface was analyzed in terms of contact angle, zeta potential, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), flux decline, and TOC removal. The contact angle of the fouled membrane surface was lower than that of the clean membrane surface. This suggests that the majority of the foulants may have been the hydrophilic organic compounds such as polysaccharides, urea, etc. which are the extracellular enzyme of microorganisms in BTSE. But, the fouled membrane surface after the pretreatment of flocculation followed by adsorption had nearly the same contact angle as that of the clean membrane, suggesting that the hydrophobicity of the membrane is preserved by this pretreatment. According to attenuated total reflection-Fourier transform infrared spectroscopy results, the peaks observed on the fouled membrane were ether (COC) and urea (RNHCONHR). On the other hand, the peaks obtained after the pretreatment of flocculation followed by adsorption were similar to those of clean membranes. The highest effluent organic matter (EfOM) concentration on the fouled membranes without any pretreatment was measured up to 0.011 mg EfOM/cm 2 membrane surface. The pretreatment of flocculation followed by adsorption reduced the EfOM concentration on the membrane to 0.005 mg EfOM/cm 2. The SEM images on the membrane cross-section revealed that there was practically no foulant layer on the membrane when a pretreatment of flocculation followed by adsorption was used.

The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization

Ultrafiltration alone can remove only a portion of the effluent organic matter (EfOM) from biologically treated sewage effluent (BTSE). Use of pretreatment not only improves the EfOM removal but also reduces the membrane fouling. In this research, NTR 7410 ultrafiltration membrane was employed to remove EfOM from BTSE. Different pretreatments namely FeCl 3 flocculation and powder activated carbon adsorption were evaluated. The highest removal of organic matter was observed when flocculation followed by adsorption was used as pretreatment. The flocculation and adsorption removed 68.5% and 71.4% of hydrophobic organics, respectively. The molecular weight (MW) of the EfOM in BTSE ranged from 300 to about 400,000 Da. After the flocculation pretreatment, the majority of large MW organic matter was removed. The pretreatment of the flocculation followed by adsorption led to very high removal of both small and large organic matter. Further, this pretreatment led to practically no filtration flux decline.