Bioremediation of 2-chlorophenol containing wastewater by aerobic granules-kinetics and toxicity

2-Chlorophenol (2-CP) degrading aerobic granules were cultivated in a sequencing batch reactor (SBR) in presence of glucose. The organic loading rate (OLR) was increased from 6.9 to 9.7 kg COD m(-3)d(-1) (1150-1617 mg L(-1)COD per cycle) during the experiment. The alkalinity (1000 mg L(-1) as CaCO(3)) was maintained throughout the experiment. The specific cell growth rate was found to be 0.013 d(-1). A COD removal efficiency of 94% was achieved after steady state at 8h HRT (hydraulic retention time). FTIR, UV, GC, GC/MS studies confirmed that the biodegradation of 2-CP occurs via chlorocatechol (modified ortho-cleavage) pathway. Biodegradation kinetics followed the Haldane model with kinetic parameters: V(max)=840 mg2-CPgMLVSS(-1)d(-1), K(s)=24.61 mg L(-1), K(i)=315.02 mg L(-1). Abiotic losses of 2-CP due to volatilization and photo degradation by sunlight were less than 3% and the results of genotoxicity showed that the degradation products are eco-friendly.     

Aerobic granulation for wastewater bioremediation: A review

Rapid industrialisation and urbanisation releases numerous toxic compounds into natural water bodies, polluting these pristine fresh water resources. This is a subject of great concern, and the attention of environmentalists around the world has been increased towards this problem in recent years. Several techniques have been proposed for efficient wastewater treatment, most of them presenting some limitations, such as poor capacity, the generation of waste products, incomplete mineralisation and a high operating cost. Currently, aerobic granulation treatments are considered to be the most effective and economic alternative. Aerobic granulation is a process of microbial self‐immobilisation that results into a cell‐structured shape, characterised by dense biomass. Aerobic granules have a number of advantages over conventional bioflocs, such as a round and compact structure, good settling ability, high biomass retention and the ability to withstand high organic loading rates. Aerobic granulation technology has been demonstrated to be useful for a wide variety of wastewaters, including industrial, nutrient‐rich and toxic. This paper presents a state‐of‐the‐art review of effective aerobic granulation technology for wastewater treatment selected from the point‐of‐view of basic concepts of aerobic granulation, characterisation and factors that affect aerobic granulation, demonstrating the effectiveness of the cell‐immobilisation (aerobic granulation) technique. © 2012 Canadian Society for Chemical Engineering     

Coatings of PDMS-modified epoxy via urethane linkage: Segmental correlation length,phase morphology,thermomechanical and surface behavior

Modification of an aliphatic epoxy resin with silicone was carried out through urethane route. Hydroxy-terminated polydimethylsiloxane (HTPDMS) was reacted with toluene diisocyanate to form an isocyanate-capped prepolymer. The –NCO group of the prepolymer was further reacted with –OH group of an aliphatic epoxy adipate resin, obtained by reaction of adipic acid with an epoxy resin, to obtain silicone-modified epoxy resin. Silicone-modified epoxy resins containing 15 and 30 wt% of silicone prepolymer have been synthesized by this procedure. TGA analysis of the silicone-modified epoxy resin showed considerable improvement in thermal stability over the unmodified epoxy resin. Modulated differential scanning calorimetry (MDSC) was used to find the segmental correlation length of the silicone-modified polymers. The cured films of silicone-modified resins showed biphasic morphology as evidenced from scanning electron microscopy. Further, the thermomechanical property of the samples was investigated by dynamic mechanical analysis. The surface properties of the silicone-modified matrices were studied by atomic force microscopy and contact angle goniometry. The silicone-modified samples showed considerably lower surface energy, surface roughness and contact angle hysteresis compared to the unmodified resins.     

Synthesis and characterization of high molecular weight side chain liquid crystalline/photoactive polymers

Various liquid crystalline and photoactive azobenzene monomers were synthesized and attached to copoly(methyl methacrylate‐glycidyl methacrylate) [copoly (MMA‐GMA)] to get high molecular weight side chain liquid crystalline (LC)/photoactive copolymers. Further, spacers are generated in situ and reactive groups are obtained after the modification. All monomers and polymers were thoroughly characterized by FTIR, ¹H and ¹³C NMR, UV‐VIS spectrophotometry, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy. All side chain LC polymers showed higher thermal stability than that of copoly(MMA‐GMA). Three LC and one azo monomer exhibited characteristic nematic mesophase where as one LC monomer has shown nematic and sanded smectic‐A texture. The rate of trans‐cis isomerization of polymer was lower than that of the monomer and both monomers and polymers showed slow back isomerization. Present approach offers convenient way to synthesize high/desired molecular weight photoactive LC polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009