The public demand for color-free waste discharge to receiving waters and tougher color standards have made decolorization of a variety of industrial wastes a top priority. Unfortunately, with the complicated color-causing compounds, the decolorization of these wastes is a difficult and challenging task. This article first describes the background information of dye molecules and dye waste characteristics. The methods for color measurements and standards are then discussed. Different techniques including almost all the known physical, chemical and biological techniques are described for decolorization. Each process alone may not be able to meet the requirements. A combination of these processes, for example, chemical-biological, biological-chemical, chemical-physical, chemical-chemical, etc. is often used. The formation of intermediates during the decolorization process is emphasized. These byproducts may be more toxic than the parent compounds. Thus, the extent of the mineralization in waste decolorizatio...

Decolorization of Wastewater

Cyclic AMP in prokaryotes.

http://www.dzumenvis.nic.in/Biodegradation/pdf/Interactions%20between%20fish%20larvae.pdf

Interactions between fish larvae and bacteria in marine aquaculture

Glyphosate [N-(phosphonomethyl) glycine] is a broad spectrum, post emergent herbicide and is among the most widely used agricultural chemicals globally. Initially developed to control the growth of weed species in agriculture, this herbicide also plays an important role in both modern silviculture and domestic weed control. The creation of glyphosate tolerant crop species has significantly increased the demand and use of this herbicide and has also increased the risk of exposure to non-target species. Commercially available glyphosate-based herbicides are comprised of multiple, often proprietary, constituents, each with a unique level of toxicity. Surfactants used to increase herbicide efficacy have been identified in some studies as the chemicals responsible for toxicity of glyphosate-based herbicides to non-target species, yet they are often difficult to chemically identify. Most glyphosate-based herbicides are not approved for use in the aquatic environment; however, measurable quantities of the active ingredient and surfactants are detected in surface waters, giving them the potential to alter the physiology of aquatic organisms. Acute toxicity is highly species dependant across all taxa, with toxicity depending on the timing, magnitude, and route of exposure. The toxicity of glyphosate to amphibians has been a major focus of recent research, which has suggested increased sensitivity compared with other vertebrates due to their life history traits and reliance on both the aquatic and terrestrial environments. This review is designed to update previous reviews of glyphosate-based herbicide toxicity, with a focus on recent studies of the aquatic toxicity of this class of chemicals.

Impact of glyphosate and glyphosate‐based herbicides on the freshwater environment

Four human-associated bacteria, Pseudomonas aeruginosa, Salmonella newport, Escherichia coli, and Klebsiella pneumoniae, were tested for survival in five freshwater sediments. Bacterial survival in continuous-flow chambers was monitored over 14-day periods on sediments ranging from organically rich high-clay fractions to organically poor sandy fractions. Bacterial die-off ranged from 1 to 5 orders of magnitude in sediments. E. coli survived as long as or longer than S. newport. P. aeruginosa and K. pneumoniae tended to survive longer than E. coli. Survival of E. coli and S. newport was greater in sediments containing at least 25% clay. Good reproducibility allowed the development of linear models to describe die-off rates.

Survival of pathogenic bacteria in various freshwater sediments.

Kueh, C.S.W. & Chan, K-Y. 1985. Bacteria in bivalve shellfish with special reference to the oyster. Journal of Applied Bacteriology, 59, 41–47.

The bacterial flora of the Pacific oyster Crassostrea gigas, the sea mussel Perna viridis and the arkshell clam Scapharca cornea differed considerably from that of seawater in both numbers and generic composition. The numbers of heterotrophic bacteria in the bivalve shellfish, including the anaerobes and spore-forming bacteria, were greater than that in the surrounding water. Pseudomonas spp. were the dominant organisms, comprising over one third of the 321 strains characterized after isolation from the bivalves and seawater. Other bacteria isolated from the shellfish included Vibrio, Acinetobacter, and Aeromonas spp., whereas the seawater flora consisted mainly of coliform organisms, coryneform bacteria and Flavobacterium/ Cytophaga spp. Bacteria associated with the deposit-feeding clams were higher in density and more distinct in generic composition as compared with those in the suspension-feeding oysters and mussels. Over 90% of the coliform and heterotrophic bacteria in oysters were found in organs associated with the digestive tract. Coliforms were mainly found in the stomach while heterotrophs were present in both stomach and the lower intestine. The results suggest that the stomach flora of oysters are mainly derived from the external environment and, through a process of selection and multiplication, that it may be gradually replaced by a more indigenous population which dominates the lower digestive tract.

Bacteria in bivalve shellfish with special reference to the oyster.

The summer prevalence of Vibrio parahaemolyticus and other halophilic vibrios in seafood from Hong Kong markets was investigated. Halophilic vibrios were isolated from all seven types of seafood examined, and comprised 9.1%, 8% and 6.1% of contaminating aerobic heterotrophic bacteria from mussels, clams and oysters respectively. Sucrose-positive vibrios were more common than sucrose-negative varieties. Vibrio alginolyticus was the most frequently isolated species, followed by V. parahaemolyticus, V. harveyi, V.fluvialis, V. vulnificus, V. pelagius, V. campbellii, V. spendidus and V. marinus. Mussels contained the highest concentration of V. parahaemolyticus (4.6×103/g); oysters and clams contained 3.4×104/g and 6.5×103/g respectively. The ubiquity and relatively high concentrations of V. parahaemolyticus and other pathogenic vibrios in shellfish is a potential public health hazard in Hong Kong and other subtropical Asian countries.

Vibrio parahaemolyticus and other halophilic vibrios associated with seafood in Hong Kong

Two hundred and forty-four clinical and environmental strains of nine species of halophilic vibrios isolated in Hong Kong were tested for their susceptibilities to 23 antimicrobial agents by an agar dilution method using unsupplemented Mueller-Hinton agar, an inoculum size of 10(5) cfu per spot and incubation for 18 h at 30 degrees C Most strains were resistant to sulphamethoxazole, trimethoprim, penicillins and older cephalosporins, and most were susceptible to chloramphenicol, tetracycline, cotrimoxazole, the aminoglycosides, the newer cephalosporins, aztreonam, imipenem and the quinolones However, there were significant differences between species, especially in their patterns of beta-lactam susceptibility

Antimicrobial susceptibilities of halophilic vibrios

Nitrogen and phosphorus removal from sewage effluent with high salinity by Chlorella salina

Decolorization and biodegradation of the azo dye methyl red (2′-carboxy-4-N,N-dimethylamino-azobenzene) in shaking and static cultures of the strict aerobe Acetobacter liquefaciens S-1 were demonstrated by the disappearance of the brownish orange color of the methyl red containing medium (pH 7.5), by the decrease in absorption maximum of methyl red, and by the identification of two compounds 2-aminobenzoic acid (anthranilic acid) and N,N′-dimethyl-p-phenylene diamine (4-N,N-dimethylamino-aniline) formed by reductive cleavage of methyl red in parallel with incubation time. Decolorization of methyl red was essentially completed within 17 h of incubation in both shaking and static cultures, which contained 1 g/L of (NH4)2SO4 as nitrogen source, 1% ethanol as carbon source, and up to 400 ppm of methyl red. Cells of A. liquefaciens S-1 were able to metabolize methyl red as sole nitrogen source for growth, although the time required to achieve high decolorization efficiency (98%) of methyl red was considerably longer (72 h) under this condition.

Kwong-Yu Chan

Papers

Bacteria in bivalve shellfish with special reference to the oyster.

Vibrio parahaemolyticus and other halophilic vibrios associated with seafood in Hong Kong

Antimicrobial susceptibilities of halophilic vibrios

Nitrogen and phosphorus removal from sewage effluent with high salinity by Chlorella salina

Decolorization and biodegradation of methyl red by acetobacter liquefaciens