M. Okada

Chemical properties of anion-exchangers prepared from waste natural materials

Abstract Waste natural materials (WNM) were converted into anion-exchangers through consecutive chemical reactions with thionylchloride, N,N-Dimethylformamide (DMF), dimethylamine and formaldehyde as crosslinking agents. The final products obtained were weak-base anion-exchangers with tertiary amines as major functional exchange groups. WNM containing small amounts of extractives gave higher yields. Also, anion-exchangers produced from WNM with higher lignin content gave higher maximum nitrate adsorption capacity (Qmax). Moringa oleifera (M. oleifera) hull with the highest lignin content of 30.4% showed the highest Qmax of 0.20 mmol NO3− per g of resin, followed by coconut husk, sawdust of lauan and rice hull. Anion-exchangers produced from WNM and mixtures of pure lignin and pure cellulose demonstrated that lignin is the major reactive component responsible for the anion-exchanger and cellulose seems to be a supporting material for the exchangers.

Ultrafiltration behaviour of extracellular and metabolic products in activated sludge system with UF separation process

Ultrafiltrations were conducted using a stirred batch cell for the batch culture supernatants containing extracellular and metabolic products released into culture medium from activated sludge bacteria mixture and Sphaerotilus natans strains responsible for aerobic bulking of the conventional activated sludge process. There existed differences in time-dependent relative permeate flux among growth phases for the same organisms and among the organisms grown to the same stationary growth phases, respectively. The retained ratio of protein to sugar during filtration may be one of the factors affecting the magnitude of time-dependent relative permeate flux decline, suggesting different degrees of interactive effect of both protein and sugar dependent on organism species and their growth phases on permeate flux decline characteristics of culture solutions.

The characteristics of the bacterial community structure and population dynamics for phosphorus removal in SBR activated sludge processes

The characteristics of the bacterial community structure and population dynamics for phosphorus removal in activated sludge were investigated using laboratory-scale sequencing batch reactor (SBR) activated sludge processes fed with four different carbon sources. Phosphorus removal activity, quinone profile of the activated sludge and isolated bacterial strains were monitored. An enhanced phosphorus removal activity was accompanied by the increase in ubiquinone-9 (Q-9). The relationships between phosphorus removal activity and Q-9 contents of the isolated bacterial strains were dependent neither on the organic substrates nor on the species of isolated bacterial strains. The enhanced phosphorus removal capability of activated sludge seemed to be due to the increase in the populations of bacteria with activity of phosphorus removal, i.e. species succession of bacteria in activated sludge ecosystems, rather than the increase in the phosphorus removal capability of phosphorus removal bacteria. Not only Acinetobacter but also Pseudomonas identified from isolated strains were regarded as representative polyphosphates-accumulating organisms and predominant species to the whole of bacterial population in activated sludge for phosphorus removal.

Characteristics of fouling due to clay-organic substances in potable water treatment by ultrafiltration

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.

Comparative effectivity of different types of neutral chelating agents for preparing chelated bagasse in solvent-free conditions

Abstract Eight different types of reagents containing chelating exchangeable groups were tested to convert sugarcane bagasse into chelating ion exchangers. Urea, melamine, thiourea, dimethylamine, polyethyleneimine, ethylenediamine, diethylenetriamine, iminodiacetic acid and glycine were irradiated with sugarcane bagasse using microwave at different reaction times. It was found that bagasse neutral chelating agents produced from thiourea (BTHI) and urea (BUREA) demonstrated nitrogen contents of 14.6% and 14.9% after 4 and 12 min of reaction, respectively. BTHI demonstrated maximum mercury adsorption capacity of 2.2 meq g−1 followed by BUREA (1.5 meq g−1) and melamine (BMEL) (0.9 mmeq g−1). Among all the reagents tested, BUREA may prove to be the more ecologically benign and inexpensive alternative procedure to prepare chelating ion exchangers. Urea has been classified as a safer reagent than thiourea.