Impact of Microcystis aeruginosa on membrane fouling in a biologically treated effluent

Abstract

Microcystis aeruginosa was cultured in biologically treated municipal effluent to simulate blue-green algal bloom conditions in a treatment lagoon. The effect of algae in the early, mid and late phases of growth on membrane fouling, chemical coagulation (alum or aluminium chlorohydrate (ACH)) and hydraulic cleaning on the microfiltration of this effluent was investigated. The effect of M. aeruginosa in the early phase was negligible and gave a similar flux profile and permeate volume to that of effluent alone. The increase in M. aeruginosa concentration for the mid and late phases caused a significant reduction in permeate volume compared with the early phase. Full flux recovery was achieved with an alum dose of 1 mg Al3+ L(-1) (early phase) and 10 mg Al3+ L(-1) (mid phase), demonstrating that membrane fouling was hydraulically reversible. For the late phase, the highest flux recovery was 89%, which was achieved with an alum dose of 5 mg Al3+ L(-1). Higher alum dosages resulted in a reduction in flux recovery. The use of 1.5 pm pre-filtration after alum treatment showed little improvement in water quality but led to a drastic reduction in flux recovery, which was attributed to diminishing the protective layer on the membrane surface, thus enabling internal fouling. The performance of ACH was comparable to alum at low dissolved organic carbon (DOC) and cell concentration, but was not as effective as alum at high DOC and cell concentration due to the formation of more compact ACH flocs, which resulted in a higher cake layer specific resistance, leading to the deterioration of performance.

Effect of feedwater pre-treatment using UV/H 2 O 2 for mitigating the fouling of a ceramic MF membrane caused by soluble algal organic matter

“…AOM has been demonstrated to cause severe fouling for low-pressure polymeric [5][6][7][8] and ceramic membranes [9,10] as it contains a high proportion of high molecular weight (MW) biopolymers such as polysaccharides and proteinaceous substances which have been identified as the most problematic foulants for the membranes. Moreover, the blooms can lead to the release of harmful algal metabolites including toxins into the drinking water, posing a threat to human health [11].…”

Influence of the characteristics of soluble algal organic matter released from Microcystis aeruginosa on the fouling of a ceramic microfiltration membrane

“…The algal organic compounds are commonly dominated by hydrophobic proteins and hydrophilic polysaccharides which have been widely regarded as responsible for the significant fouling issues in membrane filtration processes [5]. It has been demonstrated that the presence of AOM associated with natural organic matter in surface water or effluent organic matter in wastewater can further reduce the flux of polymeric MF/UF membranes [6][7][8]. Some efforts have been made since to characterise the AOM fouling of the polymeric MF/UF membranes, with a view to understanding the fouling mechanisms.…”

Treatment of secondary effluent with biological activated carbon to reduce fouling of microfiltration membranes caused by algal organic matter from Microcystis aeruginosa

“…AOM comprises mainly high molecular weight (MW) organics such as protein-like and polysaccharide-like substances [5] which can cause severe membrane fouling and lead to decrease in membrane permeability [3,4]. It has been demonstrated that the presence of AOM in addition to the effluent organic matter in secondary effluent can further reduce the efficiency of LPM filtration [6,7], thus increasing the operating cost. However, Lee and Walker [8] reported that hydrophobic polysulfone UF membrane could remove 91% of microcystin-LR whereas hydrophilic CA membranes adsorbed little or no microcystin-LR.…”