Surface modification of polypropylene macroporous membrane to improve its antifouling characteristics in a submerged membrane-bioreactor: H(2)O plasma treatment

To improve the antifouling characteristics of polypropylene hollow fiber macroporous membranes in a submerged membrane-bioreactor for wastewater treatment, the membranes were surface modified by H₂O plasma treatment. Structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). The change of surface wettability was monitored by contact angle measurement. The static water contact angle of the modified membrane reduced obviously with the increase of plasma treatment time. The total surface free energy and its dispersive component decreased, while the polar component increased with the increase of treatment time. The relative pure water flux for the modified membranes increased gradually with the increase of plasma treatment time. The tensile strength and the tensile elongation at break for the membranes decreased after plasma treatment. After continuous operation in a submerged membrane-bioreactor for about 68 h, flux recovery after water and caustic cleaning, flux ratio after fouling were improved by 2.0, 3.6 and 22.0%, while reduction of flux was reduced by 1.1% for the 1 min H₂O plasma treated membrane, compared to those of the unmodified membrane.     

Biodegradation of persistent polar pollutants in wastewater: comparison of an optimised lab-scale membrane bioreactor and activated sludge treatment

The biodegradation of selected non-adsorbing persistent polar pollutants (P(3)) during wastewater (WW) treatment was studied by comparing a lab-scale membrane bioreactor (MBR) running in parallel to activated sludge treatment (AST). The investigated P(3) are relevant representatives or metabolites from the compound classes: pesticides, pharmaceuticals, insect repellents, flame retardants and anionic surfactants. Analyses of all these P(3) at low ng L(-1) levels with sufficient standard deviations was performed in WW influents and effluents. Non-degradable micropollutants, such as EDTA and carbamazepine were not eliminated at all during WW treatment by any technique. However, the MBR showed significant better removals compared to AST for the investigated poorly biodegradable P(3), such as diclofenac, mecoprop and sulfophenylcarboxylates. An application of such an in terms of sludge retention time optimised MBR may lead to a reduction of these P(3) in the watercycle.     

Cultivation of Phanerochaete chrysosporium and production of lignin peroxidase in novel biofilm reactor systems: Hollow fiber reactor and silicone membrane reactor

The white rot fungus Phanerochaete chrysosporium and its extracellular enzyme lignin peroxidase are both known to catalyze the transformation and, in many cases, the degradation of several hazardous compounds and are, therefore, promising candidates for application in hazardous waste treatment. The application of P. chrysosporium in large-scale waste treatment and commercial production of lignin peroxidase has been impeded by the lack of bioreactor systems yielding consistent production of high levels of lignin peroxidase under long-term steady state conditions and controlled growth of the fungus. The use of innovative biofilm systems, which minimize intensive shear and provide for fungal growth as a biofilm, was investigated. The viability of the use of a hollow fiber reactor and a stirred tank reactor modified into a unique silicone membrane reactor for the cultivation of P. chrysosporium and production of high levels of lignin peroxidase was demonstrated. The membrane reactor utilizes silicone tubing as a growth support and for oxygenation. The silicone membrane reactor was operated using a repeated batch technique, consisting of alternating growth and production phases, to yield production of lignin peroxidase over a period of 5 weeks and appears promising for application as a hazardous waste treatment process.