Fouling mechanisms and reduced chemical potential of ceramic membranes combined with ozone

Abstract

Combining ceramic membranes with ozonation and allowing ozone residual to contact the membrane surface is well known to control fouling, allowing for higher membrane fluxes. This means that the more robust, longer lasting and higher integrity ceramic material can potentially be used in water recycling in a cost competitive way. This paper presents additional results from a previously reported ozonation/ceramic membrane trial in Melbourne, Australia. The results assisted in understanding the cause of the high fluxes by quenching the residual ozone upstream of the membrane, to isolate its effects on organic species from those on the membrane. Ozone quenching was directly attributed to lost membrane performance which confirmed that ozone has a direct effect on the membrane which contributes to the higher fluxes. Tests to reduce cleaning chemical use (sodium hypochlorite) at high fluxes were also conducted. Sodium hypochlorite consumption generally was not significant, but trading better stability and higher fluxes for reduced chemical use needs to be justified. Ceramic membranes coupled with pre-ozonation exhibit unique properties in water treatment, offering potential advantages such as increased backwash disinfection, as well as higher flux rates or reduced chemical consumption.

Effect of oxidation with coagulation and ceramic microfiltration pre-treatment on reverse osmosis for desalination of recycled wastewater

“…In considering ceramic membranes, high flux is important to offset their higher material cost but must be operated in a specific way to achieve this, which would impact the downstream RO plant operation. For example Dow and co-workers demonstrated that the sustainable ceramic microfiltration (CMF) membrane fluxes for treating clarified wastewater increased 2-3 fold in response to dosing with the common coagulant polyaluminium chloride (PACl) [2,3]. Coagulation used prior to polymer membranes is already known to reduce fouling as well as to remove organic matter, particularly the large molecular weight (MW) components, being biopolymers and humic substances [4][5][6].…”

“…[7] concluded that coagulation treatment reduced organic fouling by removal of these largersized materials. Further, ozone used in conjunction with coagulation and ceramic membranes was observed to work together to provide >4-fold sustainable flux increases for ceramic membranes [2]. Oxidation processes such as ozonation, and ultraviolet irradiation (UV), are commonly practised as the tertiary treatments to meet appropriate water quality in reclaimed water from secondary wastewater treatment plant (WWTP) effluents for disinfection purposes, odour treatment as well as the removal of colour caused by humic substances.…”

Small Scale Direct Potable Reuse (DPR) Project for a Remote Area

“…Ozonation, employing a strong oxidation effect of ozone on pathogen inactivation, bio-degradability improvement of organic matter, degradation of chemicals of concern (CoC), a lower chemical consumption associated with cleaning of the downstream ceramic micro-filtration (MF) and improved backwash efficiency [4,5]. 2.…”

Demonstration of membrane distillation on textile waste water: assessment of long term performance, membrane cleaning and waste heat integration

“…Caustic cleaning to remove organic fouling is expected to be effective, where previous work on caustic cleaning of polyvinylidene fluoride (PVDF) MD membranes fouled with humic acid and calcium solutions was very effective [41]. The inability of sodium hypochlorite to further restore flux is surprising, as it is well known to clean both PVDF and ceramic membranes used in low pressure filtration [43,44]. The reasons may relate to the very different membrane chemistries (hydrophobic PTFE vs hydrophilic PVDF) where the attachment of the fouling materials to the membrane work by different mechanisms [52,53], or indeed the nature of textile processing materials and their resistance to chlorine degradation.…”

“…pH 9) [42]. Sodium hypochlorite is also utilised in removing organic matter from filtration membranes [43,44] and may be suitable for MD. However experience on cleaning MD membranes after treatment of real textile wastewater is limited, and more work is needed to demonstrate effective cleaning for practical longer term operation.…”