Nichanan Tadkaew

Removal of trace organics by MBR treatment: the role of molecular properties

This study examined the relationship between specific molecular features of trace organic contaminants and their removal efficiencies by a laboratory scale membrane bioreactor (MBR). Removal efficiencies of 40 trace organic compounds were assessed under stable operating conditions. The reported results demonstrate an apparent correlation between chemical structures and the removal of trace organic contaminants by the laboratory scale MBR system. The removal of all 14 very hydrophobic (Log D > 3.2) trace organic compounds selected in this study was consistently high and was above 85%. The occurrence and types of electron withdrawing or donating functional groups appear to be important factors governing their removal by MBR treatment. In this study, all hydrophilic and moderately hydrophobic (Log D<3.2) compounds possessing strong electron withdrawing functional groups showed removal efficiency of less than 20%. In contrast, high removal efficiencies were observed with most compounds bearing electron donating functional groups such as hydroxyl and primary amine groups. A qualitative framework for the assessment of trace organic removal by MBR treatment was proposed to provide further insights into the removal mechanisms.

Effect of mixed liquor pH on the removal of trace organic contaminants in a membrane bioreactor

Experiments were conducted over approximately 7 months to investigate the effects of mixed liquor pH (between pH 5 and 9) on the removal of trace organics by a submerged MBR system. Removal efficiencies of ionisable trace organics (sulfamethoxazole, ibuprofen, ketoprofen, and diclofenac) were strongly pH dependent. However, the underlying removal mechanisms are different for ionisable and non-ionisable compounds. High removal efficiencies of these ionisable trace organics at pH 5 could possibly be attributed to their speciation behaviour. At this pH, these compounds exist predominantly in their hydrophobic form. Consequently, they could readily adsorb to the activated sludge, resulting in higher removal efficiency in comparison to under less acidic conditions in the reactor. Removal efficiencies of the two non-ionisable compounds bisphenol A and carbamazepine were relatively independent of the mixed liquor pH. Results reported here suggest an apparent connection between physicochemical properties of the compounds and their removal efficiencies by MBRs.

Is halogen content the most important factor in the removal of halogenated trace organics by MBR treatment

This study investigated the relationship between physicochemical properties (namely halogen content and hydrophobicity) of halogenated trace organics and their removal efficiencies by a laboratory scale membrane bioreactor (MBR) under stable operating conditions. The reported results demonstrated a combined effect of halogen content and hydrophobicity on the removal. Compounds with high halogen content (>0.3) were well removed (>85%) when they possessed high hydrophobicity (Log D>3.2), while those with lower Log D values were also well removed if they had low halogen content (<0.1). General indices such as the BIOWIN index (which is based on only biodegradation) or a more specific index such as the halogen content (which captures a chemical aspect) appeared insufficient to predict the removal efficiency of halogenated compounds in MBR. Experimental data confirmed that the ratio of halogen content and Log D, which incorporates two important physico-chemical properties, is comparatively more suitable.

Membrane bioreactor technology for decentralised wastewater treatment and reuse

There is a growing interest in utilising non-traditional water resources by means of water reclamation and water recycling for long term sustainability. Amongst the many treatment alternatives, membrane bioreactors (MBRs) have been seen as an effective technology capable of transforming various types of wastewater into high-quality effluent exceeding most discharge requirements and suitable for a variety of reuse applications. To date MBRs are largely restricted to centralised large scale applications, with the most common capacity of 200 ML per day or above. The aim of this paper is to review and discuss the potential and limitations of MBRs for small scale applications. Both technical and economic considerations will be delineated with respect to the future water outlook in Australia. Particular attention is also given to the impact of MBR technology on the removal of micropollutants that are of significant concern in water recycling.

Effects of salinity on the removal of trace organic contaminants by membrane bioreactor treatment for water reuse

ABSTRACT This study investigated the effects of salinity on the performance of a membrane bioreactor (MBR) system with a specific focus on the removal of trace organic contaminants. Eight trace organic contaminants were selected for this investigation. The obtained results indicated that changes in salinity in the range of 1–12 g/L have small impact on the removal of carbonaceous organic matter and total nitrogen (TN) by the MBR. The permeate water quality in terms of total organic carbon and TN slightly decreased when the system was exposed to higher salt concentration. A decrease in sludge production in saline mixed liquor was observed at salt concentration of 4 g/L, and then, microbial could adapt to the saline condition as evidenced in a gradual increase in biomass throughout this study. At a low salinity level, removal efficiencies of the selected trace organics are consistent with values previously reported in the literature. There was no significant impact of salinity on removal of the eight select...