Pilot-scale Membrane Research Articles

Multi-criteria analysis of the continuous operation of a membrane photobioreactor to treat sewage: Modeling and sensitivity analysis

Microalgae-based wastewater remediation is aligned with circular economy principals but successful large-scale facilities are scarce due to the limited knowledge of the interactions between all relevant variables and the scarce development of control and automation systems. Machine learning (ML) methods have the potential predict performance in microalgae photobioreactors, with the aim to optimize it. Some attempts have been performed under controlled lab conditions which prevents the direct application of their results to industrial scale. This study aims to develop ML models for the prediction of nutrient removal, biomass production and photosynthetic efficiency using a database obtained from 1.5-y operation of a pilot-scale membrane photobioreactor (MPBR) that treated sewage. A total of 14 inputs and 6 outputs were selected. Random forests (RF), boosted trees (BT), multilayer perceptron (MLP), support vector machine methods (SVM) were tested. The lowest prediction errors were obtained with the MLP model, allowing the developed tool to be used as an alternative to mechanistic models. Large ranges of data were used, considering the variability of factors in the diurnal cycle whose influence on the variability of the data is usually neglected. Using global sensitivity analysis (GSA), input-output relationships were verified, reflecting relevant number of variables showing significant values of Shapley Indices. Additionaly, partial dependence plots showed both linear and nonlinear depending on the selected inputs and outputs. Finally, using ML models, multi-criteria optimization of operating parameters was performed for two variants: a) optimization of operating parameters (HRT, SRT, and air flowrate (Fair)); and b) optimization of operating parameters and influent nutrient loads (HRT, SRT, Fair, nitrogen and phosphorus loading rates).

Effect of Initial pH for Polluted River Water Treatment Via Pilot Scale Membrane Photocatalytic Reactor (MPR)

Conventional technologies such as physical, chemical, and biological treatment have low efficiency, a tendency towards fouling, and use high energy consumption, respectively.Coagulation-flocculation base treatment, nearly 40-60%, during thelatest technologies as an advanced organic process (AOP) with Fenton-reagents, nearly 80-85% in dissolved organic compound (DOC) reduction, respectively. It proves that emerging technology and new green technology are needed. Therefore, the objective of this study is (i) to treat polluted rivers using pilot-scale MPRs with different initial pH of 5, 7 and 9 and adsorption-desorption time contact for 20, 30 and 40 minutes using 0.05 g/L ZnO-Kaolin loading, 225W light intensity, pressured one bargand 30 minutes’ photocatalytic reaction time. (ii) analysing the physico-chemical quality of the water before and after the treatment as turbidity, ammoniacal nitrogen (𝑁𝑁𝑁𝑁3𝑁𝑁) biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), and pH levels using the HACH method with 90.89%, 84.93%, 83.19%, 99.38%, 19.47% and 0.63% removal efficiency respectively. (iii) Analyzing the kinetic reaction between the pseudo-first and pseudo-second order models using turbidity data. In conducting the experiment, the sample of polluted river water was taken at Sungai Sembrong, Batu Pahat. From the result obtained, when pH five and time adsorption-desorption time contact for 30 minutes was the optimum condition for degrading and removing the organic matter. Moreover, it obeys the pseudo-second-order model, which relates to the chemisorption processbetween the ZnO-Kaolin and organic compounds. Overall, MPRs are claimed as a promising technology that is environment-friendly for wastewater treatment applications.

Polluted River Water Treatment Via Pilot-Scale Membrane Photocatalytic Reactor (MPR) Incorporated Zno-Kaolin Under Different Light Intensity

Polluted river water treatment utilizes a mix of physical, chemical, and biological processes and activities. Conventional systems, including coagulation, flocculation, sedimentation, filtration, and disinfection, have several limitations. Hence, the Membrane Photocatalytic Reactor (MPR) is one of the most promising methods for polluted river water treatment. ZnO-Kaolin nanoparticles served as great photocatalysts for MPR performance. This study focuses on the pilot-scale hybrid MPR treatment of polluted river water under different light intensities (100, 125, and 225 watts) and irradiation times (20, 30, and 40 minutes). The treated water quality analysis is based on the Environmental Quality Act 1974 (EQA 1974). The kinetic rate was also investigated using pseudo-first-order and pseudo-second-order models. It was found that 225 watts and 30 minutes were the optimum values. The pilot scale hybrid MPR proved to fit well with the pseudo-second-order kinetic models, suggesting that the degradation follows a chemisorption mechanism. In conclusion, we believe the hybrid MPR pilot-scale system will enhance efficiency in cleaning dirty river water, all while meeting the standards of the EQA 1974.

Treatment of simulated brominated butyl rubber wastewater using monovalent anion perm-selective membranes through selective electrodialysis

Selective electrodialysis (SED) technology utilizing monovalent anion perm-selective membranes (MAPMs) has potential in resource recovery and wastewater treatment. However, the development and production of homogeneous MAPMs with high performance and scalability pose significant challenges. This study successfully scaling up a poly(alkyl-biphenyl pyridinium)-based MAPM suitable for large-scale SED applications and applies it to the treatment of mono-/di-valent anion wastewater. The pilot-scale membrane exhibits significantly higher perm-selectivity for various mixed anion systems compared to the commercial ACS membrane, and under the conditions of a current density of 40 mA cm−2, an initial dilute chamber solution of 3 L 0.5 mol/L NaCl, and a constant concentration chamber volume of 0.2 L, the pilot-scale membrane achieves a salt (NaCl) concentration of 18.6 wt% in just 70 mins in the membrane stack, with an energy consumption of 0.38 kWh kg−1. Furthermore, simulated brominated butyl rubber wastewater is treated with the aim of refining NaBr and separating SO42- ions. Several factors, such as applied voltage, initial concentration of the dilute chamber solution, feed flow rate, and dilute-to-concentrated chamber volume ratio are investigated to assess their effects on the treatment results. By continuously optimizing the operating conditions, a NaBr product with a concentration ratio of 6.2 and a purity of 97.8 % was obtained, with the Br- ion flux of 3.24 mol m-2 h−1 and an energy consumption of 0.319 kWh kg−1.

Evaluation of the shear stability of aerobic granular sludge from a pilot-scale membrane bioreactor: Establishment of a quantitative method

This work established a quantitative method to access the shear stability of aerobic granular sludge (AGS) and validated its feasibility by using the mature AGS from a pilot-scale (50 tons/day) membrane bioreactor (MBR) for treating real municipal wastewater. The results showed that the changing rate (ΔS) of the peak area (S) of granule size distribution (GSD) exhibited an exponential relationship (R2≥0.76) with the shear time (y=a−b·cx), which was a suitable indicative index to reflect the shear stability of different AGS samples. The limiting granule size (LGS) was defined and proposed to characterize the equilibrium size for AGS after being sheared for a period of time, whose value in terms of Dv50 showed high correlation (R2=0.92) with the parameter a. The free Ca2+ (28.44–34.21 mg/L) in the influent specifically interacted with polysaccharides (PS) in the granule's extracellular polymeric substance (EPS) as a nucleation site, thereby inducing the formation of Ca precipitation to enhance its Young's modulus, while Ca2+ primarily interacted with PS in soluble metabolic product (SMP) during the initial granulation process. Furthermore, the Young's modulus significantly affected the parameter a related to shear stability (R2=0.99). Since the parameter a was more closely related (R2=1.00) to ΔS than that of the parameter b or c, the excellent correlation (R2=0.99) between the parameter a and the wet density further verified the feasibility of this method.

Towards Optimisation of Microalgae Cultivation through Monitoring and Control in Membrane Photobioreactor Systems

This research lays a foundation for optimised membrane photobioreactor performance and introduces novel control parameters crucial for advancing microalgae cultivation techniques and promoting environmental sustainability. Particularly, this study presents an innovative solids retention time (SRT) controller designed for a pilot-scale membrane photobioreactor. Employing a fuzzy-logic knowledge-based approach, this controller uses the first derivative of pH data dynamics (pH′) as an input variable, directly correlated with nitrogen recovery rate and biomass productivity when normalised by average light irradiance (I2). Through a feedback mechanism, it regulates daily SRT variations, ensuring stable reactor operation, optimal volatile suspended solids concentration, efficient nitrogen removal, and enhanced biomass productivity. Normalised nitrogen recovery rate, considering solar light irradiance and volatile suspended solids concentration, increased by 51% compared to previous studies employing fixed SRT and hydraulic retention time (HRT). Combining this SRT controller with a previously studied HRT controller could potentially amplify biomass productivity efficiency. In addition, controlling or not controlling the HRT and SRT are assessed in terms of filtration performance and GHG emissions. Finally, a new dissolved-oxygen-based parameter shows promise for continuous microalgae culture control.

Optimizing Operational Conditions of Pilot-Scale Membrane Capacitive Deionization System

In this study, we developed a pilot-scale membrane capacitive deionization (MCDI) system for treating mildly brackish water and examined various operational parameters, including module arrangements, adsorption/desorption times, and flow rates. As we aimed to optimize these parameters to increase total dissolved solids (TDS) removal efficiency, the results revealed that the dual-series mode module arrangement and an adsorption time of 120 s with a flow rate of 10 L/min achieved the highest TDS removal efficiency of 99%. Energy consumption analysis showed that lower flow rates were associated with higher TDS removal efficiencies, highlighting the balance between energy consumption and water quality. This study provides insights into optimizing a pilot-scale MCDI for efficient water supply solutions, offering promise for sustainable and eco-friendly water treatment.

Pore structure regulation and continuous preparation with VNIPS process of membranes for bioseparation

Ultrafiltration technology has found widespread application in bioprocessing, particularly in protein concentration and buffer exchange for downstream processes. The demand for this technology has spurred research efforts to develop excellent membrane structures with superior separation functionality. However, challenges persist in transitioning laboratory research to industrial-scale continuous production processes while simultaneously optimizing membrane structure and performance through a single fabrication method. Thus, there is an urgent need for pilot-scale membrane preparation to improve membrane morphology and separation efficiency while ensuring scalability. This study investigates a continuous membrane fabrication method, systematically exploring the influence of different additives and vapor-assisted nonsolvent induced phase separation (VNIPS) on the structure and performance of polyethersulfone (PES) membranes. Evaluations of PES membranes with distinct structures were performed, employing flux decline, resistance analysis, and alkali resistance tests to distinguish their performance and bioseparation capabilities. The results showed that good sponge-like pore structure was obtained by VNIPS process, which realized the synergistic optimization of permeation and retention properties. Besides, the sponge-like porous structure membranes prepared by amphiphilic copolymer additives are more suitable for bioseparation.

Greywater treatment performance of a pilot-scale membrane bioreactor and characteristics of bacterial biofilm signatures in permeate effluent

Treated greywater has a high potential for water reuse. However, the post-treatment processes of reclaimed greywater may face biofouling problems due to biofilm formation. In the present study, the greywater treatment performance of a pilot-scale membrane bioreactor (MBR) was evaluated, and the effect of a dominant bacterial biofilm growing on the Pall ring media placed in the permeate pipeline was investigated. The MBR was operated for 125 days with a constant hydraulic retention time of 2 days under complete sludge retention. The treatment performance in terms of the levels of organic compounds, ammonium nitrogen, suspended solids, total coliforms, and Escherichia coli was >90 %. During the operation, a high relative abundance (>70 %) of the following bacterial phyla was observed within the MBR and the bacterial biofilm: Proteobacteria, Chloroflexi, Actinobacteria, and Planctomycetes. Furthermore, the following bacterial orders were predominantly observed in the biofilm: Sphingomonadales, Burkholderiales, and Planctomycetes. Acidovorax, Methylibium, Blastomonas, and Planctomyces were the important genera identified in the biofilm. Interestingly, the present study revealed that these bacterial species were predominant and well adapted in treated greywater containing various surfactant and detergent components. Knowledge of the predominant bacterial species in the biofilm could enable to select the appropriate disinfection method and prevent the biofouling of the reverse osmosis (RO) membrane, which can facilitate further application of the MBR-RO process for water reuse.

Temporal performance indicators for an integrated pilot-scale membrane distillation-concentrated solar power/photovoltaic system

Management of concentrate streams in inland applications has uncertain long-term environmental impacts. This study investigates an intensified solar-energy capture desalination system that integrates membrane distillation (MD) with a hybrid concentrated solar power (CSP)/photovoltaic (PV) collector to realize self-sustained zero-waste discharge for effective management of concentrate streams in inland and off-grid applications. The demonstration-scale CSP/PV system can produce up to 178 kWh of thermal energy and 4 kWh of electrical energy per day. The thermal and electrical energy from the CSP/PV system is directly supplied to the air gap MD (AGMD) pilot-scale system producing up to 288 L of distilled water per day. Experiments were performed on the hybrid AGMD-CSP/PV system to evaluate system performance under various operating conditions including AGMD and CSP flow rates, CSP system pre-heating, and AGMD vacuum pressure. Experimental results indicate that doubling the AGMD flow rate results in a 119% increase in thermal energy utilization and a 71% increase in distillate production. Compared to the winter months, operating the system in summer months when direct normal irradiance (DNI) is highest results in nearly double the distillate production (88 L in winter and 168 L in summer) and nearly three times the amount of thermal energy consumption (15 kWh in winter and 43 kWh in summer). Operating with vacuum resulted in a 34% increase in distillate production and allowing the thermal storage reservoir to preheat in the winter resulted in a 61% increase in distillate production. Overall, experimental results highlight the tradeoff between distillate production and thermal and electrical energy production and consumption under various environmental conditions and the potential for AGMD-CSP/PV to be a stand-alone desalination system.

Polymer/ionic liquid pilot scale membrane prototype for the recovery of difluoromethane (R-32) from refrigerant mixtures

Difluoromethane (R-32) is a hydrofluorocarbon (HFC) that has been massively used over the last 30 years in refrigeration and air conditioning as a primary component of azeotropic or close boiling refrigerant mixtures. Despite environmental directives commanded to drastically reduce the use of HFCs, R-32 has excellent thermodynamic properties and moderate GWP, thus its recovery from depleted mixtures collected from end-of-life equipment is sought to synthesize alternative low-GWP refrigerant blends. Membrane separation using composite polymer/ionic liquid membranes based on poly-ether-block-amide have shown potential to separate R-32 from other fluorinated hydrocarbons, yet the development of this type of composite membranes still remains at laboratory scale. In this work, a spray coating technique was successfully applied to create defect-free thin selective layers of neat Pebax®1657, Pebax®1657/40 wt% [C2C1im][BF4] and Pebax®1657/40 wt% [C2C1im][SCN] coated on porous PVDF substrates. This methodology was transferred from the lab-scale tests (12.6 cm2) to a custom pilot set-up (300 cm2). The pilot results confirmed the superior performance and stability of [C2C1im][SCN]-based membranes, which allowed the recovery of up to 64.3% and 67.1% R-32 from the refrigerant mixtures R-410A (69.8 mol % R-32 and 30.2 mol % R-125) and R-454B (82.1 mol % R-32 and 17.9 mol % R-1234yf) at 6 bar, increasing the R-32 permeate concentration up to 89.6 and 95.9 mol %, respectively. These results highlight the need to expand the knowledge of this type of gas separation membranes towards thinner and defect-free selective dense layers with the purpose of approaching their real applications.

Integrated microalgae-bacteria modelling: application to an outdoor membrane photobioreactor (MPBR)

A mechanistic model describing the key interactions occurring in microalgae-bacteria consortia systems was developed and validated. The proposed model includes the most relevant features of microalgae, such as light dependence, endogenous respiration, growth, and nutrient consumption for different nutrient sources. The model is coupled to the plant-wide model BNRM2, including heterotrophic and nitrifying bacteria, and chemical precipitation processes, among others. A major novelty of the model is microalgae growth inhibition by nitrite. Validation was conducted using experimental data from a pilot-scale membrane photobioreactor (MPBR) fed with permeate from an anaerobic membrane bioreactor (AnMBR). Three experimental periods dealing with different interactions between nitrifying bacteria and microalgae were validated. The model was able to accurately represent the dynamics occurring in the MPBR, predicting the relative abundance of microalgae and bacteria over time. Specifically, >500 pairs of experimental and modeled data were evaluated, giving an average R2 coefficient of 0.9902. The validated model was also used to evaluate different offline control strategies for enhancing process performance. For example, partial-nitrification resulting in NO2-N accumulation (i.e., microalgae growth inhibition) could be avoided by increasing biomass retention time from 2.0 to 4.5 days. It has been also concluded that microalgae biomass growth rate could be also enhanced by punctually increasing the dilution rate, allowing to outcompete nitrifying bacteria.

The Pilot-Scale Membrane Distillation Systems for Wastewater Treatment: A Mini-Review

Industrial wastewater includes large amounts of contaminants thus, the wastewater must be treated prior to disposal. Moreover, since a substantial volume of wastewater is generated, environmental considerations should include the reutilizing of reclaimed water. Since industrial wastewater consists mostly of chemicals and persistent contaminants, it must be adequately treated with eco-friendly technology. Membrane technologies, specifically membrane distillation, are frequently employed in the treatment of industrial wastewater due to their significant benefits over typical wastewater remediation approaches. The substantial investigation completed to date has been undertaken on a lab scale, however, both full and pilot-scale practices have already been implemented progressively. This study presents a concise overview of industrial wastewater treatment and its utilization following proper handling by membrane processes in both full and pilot-scale relevance. In addition, the future prospects and existing obstacles for membrane processes, including cleansing techniques and financial impact, are also studied. In addition, given that there are fewer full-scale trials than pilot-scale studies, process flaws are highlighted to facilitate future research investigations.

Performance evaluation of a pilot-scale membrane filtration system for oily wastewater treatment: CFD modeling and scale-up design

The discharge of oily wastewater into the environment adversely impacts the ecosystem and human health due to the existence of toxic and carcinogenic compounds in oil. To decrease the destructive environmental impacts, membrane filtration technology has been used because it can remove emulsified oil with droplet sizes ranging from 1 to 10 μm which is a challenging issue for other types of treatment methods. In this research, a comprehensive 3D CFD model was developed to investigate the oily wastewater treatment process in a pilot-scale membrane filtration system. The model was validated using available data in experimental runs such as oil removal efficiency and average transmembrane pressure (TMP) for two types of oily wastewater containing heavy and light crude oils. Following that, the hydrodynamic condition of the pilot-scale unit was analyzed which is difficult to be investigated in a real condition. The impacts of inlet oil concentration, permeate, and aeration flow rates on permeate oil concentration and TMP were also evaluated. Results revealed when the inlet oil concentration was at the threshold of 270 and 330 mg/L containing heavy and light crude oil, respectively, the system met the International Convention for the Prevention of Pollution from Ships (MARPOL) 73/78 regulation. Additionally, the model was capable of predicting TMP changes under constant flux. Finally, the validated model was used to upscale the pilot-scale system to achieve a permeate production rate of 10,000 L/h for larger capacities. Based on the results, the oil removal efficiency was above 88 % in pilot and upscaled systems.

Integration of Pre-Treatment with UF/RO Membrane Process for Waste Water Recovery and Reuse in Agro-Based Pulp and Paper Industry

This recent study aims to evaluate the efficacy of membrane filtration on recovery of water resource from agro-waste such as bagasse, crop-based pulp and paper mill waste. A mini pilot scale membrane system having a combination of pre-treatment filter unit (pre-filter, sediment filter and pre-carbon filter), ultra-filtration and reverse osmosis with spiral wound configuration were employed to evaluate the water reuse efficacy of effluent coming from the secondary clarifier of the conventional treatment plant of the mill. The operational conditions were optimized using Taguchi method at pH 8, temperature 32 °C, and pressure 2 bar and a flow rate of 60 l/hr. The qualities of the effluent from the secondary clarifier, and the permeate from both the combination, viz. Combination 1 (pre-treatment + ultra-filtration) and Combination 2 (pre-treatment + ultra-filtration+ reverse osmosis) were analyzed and the percentage reduction in pH, TDS, TSS, BOD, COD, Color, Lignin, Potassium and Sodium were calculated. The elimination of TDS, COD and BOD with Combination 1 was not promising (<22%). However, the installation of a RO membrane greatly reduced (>88%) the contaminants in both paper mill effluents. The obtained qualities of water from all the combinations were compared with the tolerance standard for reuse as process water. The quality of effluent from the secondary clarifier did not agree with any class of water quality. The permeate from the combination of pre-treatment and UF sufficiently reduced the TSS to reach the requirement. However, the combination of (pre-treatment + UF + RO) adequately complied with the quality standard required for reuse in the making of all grades of paper.

Performance of pilot-scale membrane aerated biofilm reactors integrated with anoxic nano-biotechnological reactor for domestic wastewater treatment

Membrane-aerated biofilm reactors (MABRs) have aroused increasing attention due to their excellent performance in treating wastewater, where the membranes behave as bio-carriers for microorganisms and bubbleless air diffusers. The MABR technology has not been fully commercialized due to reactor design and low total nitrogen (TN) removal efficiency at short hydraulic retention times (HRT). In this study, a hybrid system of MABR 1 integrated with an anoxic nano-biotechnological reactor filled with Granulated Nanoscale Oxyhydroxides of Fe (GNOF) media was evaluated to assess the improvement in nitrogen removal performance at 12, 10, and 4 h of HRTs. At the same time, another MABR (MABR 2) was operated individually at 12, 10, 8, 6, 4, and 2 h of HRTs to assess the influence of HRT on nitrogen removal performance. An enhancement in removal performance was reported in the hybrid MABR-GNOF, achieving the highest removal efficiencies of 74.3 ± 3.1% for ammonium nitrogen (NH4+-N), 69.8 ± 2.1% for total nitrogen (TN), and 90.9 ± 1.7% for chemical oxygen demand (COD), at 12 h HRT. The hybrid MABR-GNOF system attained 18% higher nitrogen removal than the MABR-only system at 12 h of HRT. A simultaneous anoxic nitrification-denitrification and COD oxidation might be developed for the removal of COD, NH4+-N, and TN from domestic wastewater by using GNOF as an electron acceptor in the hybrid MABR-GNOF unit. The findings in this study confirmed the possibility of integration of GNOF and MABR on a pilot scale and are promising for the application of this hybrid system on a full scale.

Temporal Performance Indicators for an Integrated Pilot-scale Membrane Distillation-concentrated Solar Power/photovoltaic System

Temporal Performance Indicators for an Integrated Pilot-scale Membrane Distillation-concentrated Solar Power/photovoltaic System

Quantitative and qualitative variations of biopolymers in a pilot-scale membrane bioreactor treating municipal wastewater throughout 3 years of operation

In this study, the fouling potential of mixed liquor suspension samples collected from a pilot-scale membrane bioreactor (MBR) that treated municipal wastewater was monitored for more than 3 years. The fouling potential was assessed by batch filtration experiments using the same type of membrane as equipped in the MBR. The fouling potential increased when the temperature of the mixed liquor suspension in the MBR decreased. However, the polysaccharide and protein concentrations in the mixed liquor suspension, which have been focused on many previous studies, did not correlate with the fouling potential (R2 = 0.15 and 0.39, respectively). In contrast, the concentration of biopolymers, quantified by liquid chromatography–organic carbon detection (LC-OCD), exhibited a marked correlation with the fouling potential (R2 = 0.89). A high concentration of biopolymers with large molecular weight (>1 million Da) was likely responsible for the high fouling potential. Fourier transform infrared (FTIR) analysis of the dissolved organic matter in the mixed liquor suspension indicated that the chemical properties of the biopolymers considerably varied with the seasonal temperature variation, which has rarely been reported and gives insights into fouling in MBRs. The effect of temperature on the biopolymer concentration and molecular weight of biopolymers was also investigated in a separate bench-scale experiment in which temperature was controlled. It was clearly shown that a low temperature induced an increase in the biopolymer concentration and an associated increase in the fouling potential of the mixed liquor suspension.

Membrane contactor onsite piloting for nutrient recovery from mesophilic digester reject water: The effect of process conditions and pre-treatment options

Nutrient recovery is an important segment of the circular economy, and it significantly contributes to sustainable development goals. This work reports on the outcomes of a field testing pilot-scale membrane contactor system designed for nitrogen (N) and phosphorous (P) recovery in the form of high purity ammonium salts and high-quality P containing sludge. The pilot testing was conducted at the Viikinmäki WWTP using digester reject water under different treatment conditions. Our system showed a high tolerance for solids (concentration > 500 mg/L). Field test trials showed that the higher the feed flow, the better the ammonia transfer rate. Decreasing the retention time from 4 h to 2 h increased the ammonia mass transfer rate constant by >150 %. Among the tested feed pH levels, a pH of 10 had the highest solids removal, which in turn resulted in the highest ammonia recovery percentage. A high acid concentration lowered the ammonia transfer rate. Strong acids such as HNO3 and H2SO4 had a higher ammonia recovery than that of H3PO4. Pre-treating feedwater with starch resulted in the same ammonia accumulation rate as a poly-aluminum chloride (PAX)/polymer pre-treatment. The highest PO4−3 removal of 99 % was achieved with a PAX/polymer treatment at pH 10, whereas the highest total phosphorous removal of 77 % was achieved with a starch treatment. The produced sludge consists mainly of CaCO3 emanating from the used lime, which can be used as a soil amendment. The produced ammonium salts were of high purity and have a nutrient content comparable to that of commercial fertilizers. This study provides important insights into the selection of process parameters of membrane contactor systems based on the goal of the treatment, whether it be nutrient removal or recovery.

Ceramic membrane filtration of skim milk for the production of a casein-enriched permeate

The protein composition of skim milk was adjusted using a pilot-scale membrane microfiltration system to produce a casein-enriched permeate with a ratio of casein to serum protein close to 1:1. Microfiltration was performed at 50 °C to a volume concentration factor of 3 followed by 2 diafiltration steps. Three different membrane pore sizes (0.10, 0.14 and 0.20 μm) were used to compare the separation effect, then the effect of three different transmembrane pressures (100, 120 and 150 kPa) on protein composition in the permeate was studied. Membranes of 0.10 and 0.14 μm retained most of the casein. The 0.20 μm membrane allowed casein to pass through and made the ratio of casein to serum protein in the permeate close to 50:50 with a mean flux of 128.3 kg m−2 h−1 at 120 kPa, demonstrating the potential application of a 0.20 μm membrane to produce a new dairy ingredient.