Nicholas P. Hankins

High strength domestic wastewater treatment with submerged forward osmosis membrane bioreactor

Forward osmosis membranes are less prone to fouling with high rejection of salts, and the osmotic membrane bioreactor (OMBR) can be considered as an innovative membrane technology for wastewater treatment. In this study, a submerged OMBR having a cellulose triacetate membrane, with the active layer facing the feed solution configuration, was operated at different organic loading rates (OLRs), i.e., 0.4, 1.2 and 2.0 kg-COD/(m(3)·d) with chemical oxygen demand (COD) concentrations of 200 mg/L, 600 mg/L and 1,000 mg/L, respectively, to evaluate the performance on varying wastewater strengths. High organic content with sufficient amount of nutrients enhanced the biomass growth. High OLR caused more extrapolymeric substances production and less dewaterability. However, no significant differences in fouling trends and flux rates were observed among different OLR operational conditions.

Membrane fouling and performance evaluation of conventional membrane bioreactor (MBR), moving biofilm MBR and oxic/anoxic MBR.

In this study, three laboratory scale submerged membrane bioreactors (MBRs) comprising a conventional MBR (C-MBR), moving bed MBR (MB-MBR) and anoxic-oxic MBR (A/O-MBR) were continuously operated with synthesized domestic wastewater (chemical oxygen demand, COD = 500 mg/L) for 150 days under similar operational and environmental conditions. Kaldnes(®) plastic media with 20% dry volume was used as a biofilm carrier in the MB-MBR and A/O-MBR. The treatment performance and fouling propensity of the MBRs were evaluated. The effect of cake layer formation in all three MBRs was almost the same. However, pore blocking caused a major difference in the resultant water flux. The A/O-MBR showed the highest total nitrogen and phosphorus (PO4-P) removal efficiencies of 83.2 and 69.7%, respectively. Due to the high removal of nitrogen, fewer protein contents were found in the soluble and bound extracellular polymeric substances (EPS) of the A/O-MBR. Fouling trends of the MBRs showed 12, 14 and 20 days filtration cycles for C-MBR, MB-MBR and A/O-MBR, respectively. A 25% reduction of the soluble EPS and a 37% reduction of the bound EPS concentrations in A/O-MBR compared with C-MBR was a major contributing factor for fouling retardation and the enhanced filtration capacity of the A/O-MBR.

Performance evaluation and bacterial characterization of membrane bioreactors.

A bench-scale conventional membrane bioreactor (C-MBR), a moving bed membrane bioreactor (MB-MBR) and an anoxic/oxic membrane bioreactor (A/O-MBR), operating under similar feed, environmental and operating conditions, were each evaluated for their treatment performance and bacterial diversity. MBRs were compared for the removal of organics (COD) and nutrients (N and P) while pure culture techniques were employed for bacterial isolation and an API 20E kit was used to identify the isolates. Pseudomonas aeruginosa, selected as a representative of denitrifying microorganisms, was isolated only from the A/O-MBR using Citrimide Agar. Using PCR, the nitrifying bacteria Nitrosomonas europaea was detected only in the MB-MBR. On the other hand, Nitrobacter winogradskyi was detected in all three reactors. Addition of media and maintenance of a lesser DO resulted in the highest TN removal in the A/O-MBR as compared to the C-MBR and the MB-MBR, whereas better nitrification was observed in the MB-MBR than in the C-MBR.

Insight into the effect of organic and inorganic draw solutes on the flux stability and sludge characteristics in the osmotic membrane bioreactor

In this study, chloride based (CaCl2 and MgCl2) and acetate based (NaOAc and MgOAc) salts in comparison with NaCl were investigated as draw solutions (DS) to evaluate their viability in the osmotic membrane bioreactor (OMBR). Membrane distillation was coupled with an OMBR setup to develop a hybrid OMBR-MD system, for the production of clean water and DS recovery. Results demonstrate that organic DS were able to mitigate the salinity buildup in the bioreactor as compared to inorganic salts. Prolonged filtration runs were observed with MgCl2 and MgOAc in contrast with other draw solutes at the same molar concentration. Significant membrane fouling was observed with NaOAc while rapid flux decline due to increased salinity build-up was witnessed with NaCl and CaCl2. Improved characteristics of mixed liquor in terms of sludge filterability, particle size, and biomass growth along with the degradation of soluble microbial products (SMP) were found with organic DS.

Surfactant and Polymer-Based Technologies for Water Treatment

Water provision is essential for domestic and industrial activity. With population growth and industrialisation, the access to affordable clean water has become a pervasive problem. To tackle the problem, a considerable amount of research has been targeted on developing robust decontamination technologies that can treat wastewater at lower cost, using less energy and with a minimum chemical usage and associated impact on the environment. In this contribution, we highlight several surfactant and/or polymer-based technologies which have been developed over the past few decades for water treatment. Among these emerging technologies, polymer–surfactant complexation and flocculation is emerging as a new, economical and sustainable process for removing the contaminants from dilute aqueous solutions, and then recovering them into a highly concentrated valuable product, before recycling the polymer and surfactant in the next cycle without deterioration of treatment performance. Both membrane-based and nonmembrane-based technologies are addressed.

Introduction to Membrane Processes for Water Treatment

A wide variety of membrane processes are used for water treatment and purification, corresponding to a wide variety of membrane materials and characteristics. Important processes include reverse osmosis, nanofiltration, ultrafiltration, microfiltration and electrodialysis. The most important module types are spiral wound, hollow fibre and tubular. For all these processes and modules, membrane performance relates water flux to applied pressure, and both concentration polarisation and fouling can have a deleterious effect. In practice, membrane water treatment plant involves several unit operations to allow for pretreatment and fouling mitigation. Although strategies can be implemented to mitigate fouling, cleaning is often necessary. In spite of these challenges, membrane processes have a promising future in sustainable water processing.

Submerged and Attached Growth Membrane Bioreactors and Forward Osmosis Membrane Bioreactors for Wastewater Treatment

As an emerging technology, membrane bioreactors (MBRs) are considered to be one of the most promising wastewater treatment options in the twenty-first century for water reclamation and reuse and for meeting stringent effluent discharge standards. Membrane modules are traditionally configured as submerged units inside the bio-tank, known as submerged MBRs (SMBRs). In the recent past, the MBR process has been modified by the addition of biofilm (BF) carriers in moving or fixed bed configurations in the bioreactor, known as BF or attached growth MBR (AMBR). The AMBR combines the biologically degradative advantages of BFs with the processing efficiency of an MBR to overcome the known limitations of the SMBR. Over the past decade, research groups have focused their investigations on the AMBR, due to its superior efficiency in organic and nutrients removal and the prolonged filtration performances. Forward osmosis MBRs (FOMBRs) have also emerged quite recently, and add to MBRs two principal advantages: (1) the absence of an applied hydraulic pressure allowing a lower fouling tendency and lower energy consumption and (2) the possibility of direct water production of quality comparable to that of reverse osmosis This chapter presents an up-to-date and comprehensive review of assisted and pure BF MBR processes, examines the range of BF support media available and assesses the issues of membrane fouling, sludge characteristics and treatment performances in AMBR as compared with SMBR. It also examines the progress made to date on FOMBRs, including the types of FO membranes, the draw solutions developed and the results of process studies on water flux, fouling and water quality.

Operating Conditions Corresponding to Optimal Final Properties of Activated Sludge Using the DOE and RSM Techniques

Abstract This paper presents the influence of four relevant factors on the flocculation behavior in the activated sludge process: organic loading rate (COD), solid retention time (SRT), dissolved oxygen (DO), and calcium ion concentration, and links them to a selected set of process responses: sludge volume index (SVI), turbidity, organic removal rate (COD), and suspended solids (SS) removal. The “Design of Experiments” (DOE) and the “Response Surface Methods” (RSM) approaches are used to establish the operating conditions corresponding to optimal final properties of the activated sludge. Using these techniques, the results show that it is indeed feasible to locate the operating conditions which optimize the flocculation process and the sludge settling properties. The study represents a first attempt to evaluate the flocculation process in activated sludge using the DOE/RSM approach.

Influences of ammonium and phosphate stimulation on metalworking fluid biofilm reactor development and performance

In this study, the effects of common wastewater stimulants, namely NH4Cl and KH2PO4, on the development and performance of metalworking fluid biofilm bioreactors are presented. It is shown that biofilms flourished only when one of these components was present in limiting quantities. Biofilm yields significantly declined when both of the components were withheld from the bioreactors or when both components were provided in excess. Stimulations to the reactors using NH4Cl significantly reduced the total carbon removal performance, while stimulations using KH2PO4 resulted in significant increases in performance. Chromatographic analyses showed that the NH4Cl stimulation enhanced the removal of saturated fatty amides and diethylene glycol butyl ether from the metalworking fluid, but inhibited the removal of diisoproponolamine. Furthermore, NH4Cl additions inhibited the oil/water separation carbon removal mechanism and resulted in the re-dispersion of recalcitrant organic material. The results from this study show that metalworking fluid practitioners should take care in choosing the nutrients used for stimulating bioreactor performance and microbe development. Incorrect stimulations with NH4Cl may result in negative treatment performances due to the inhibition of amine utilisation and enhancing emulsion stability.

Forward Osmosis for Sustainable Water Treatment

Forward osmosis (FO) as an emerging technology has been researched extensively over the past few decades for water treatment and other applications. In FO, the water in the feed solution (at low osmotic pressure) spontaneously flows through a semipermeable membrane to the draw solution (at high osmotic pressure) under the osmotic pressure difference and without applied hydraulic pressure, conferring the advantages of low energy consumption in the separation process and reduced membrane fouling. For this reason, it is a promising potential candidate for sustainable water processing.