Effect of addition of pond ash and fly ash on properties of ash-clay burnt bricks.

Two industrial solid waste products generated by Indian coal-fired power plants, namely pond ash and fly ash, were used in combination with local clay to develop building bricks. The clay were mixed with the two different ashes in the range 10 to 90 wt.%, hydraulically pressed and fired at 1000 degrees C. The fired products were characterized for various quality properties required for building bricks. The properties of the optimal compositions were compared with conventional red clay bricks including the developed microstructures and the comparative study generally showed that te ash-clay bricks were of superior quality to the conventional products.     

Evaluating a drinking-water waste by-product as a novel sorbent for arsenic

Arsenic (As) carcinogenicity to humans and other living organisms has promulgated extensive research on As treatment technologies with varying levels of success; generally, the most efficient methods come with a significantly higher cost burden and they usually perform better in removing As(V) than As(III) from solution. In the reported study, a novel sorbent, a waste by-product of the drinking-water treatment process, namely, drinking-water treatment residuals (WTRs) were evaluated for their ability to adsorb both As(V) and As(III). Drinking-WTRs can be obtained free-of-charge from drinking-water treatment plants, and they have been successfully used to reduce soluble phosphorus (P) concentrations in poorly P-sorbing soils. Phosphate and arsenate molecules have the same tetrahedral geometry, and they chemically behave in a similar manner. We hypothesized that the WTRs would be effective sorbents for both As(V) and As(III) species. Two WTRs (one Fe- and one Al-based) were used in batch experiments to optimize the maximum As(V) and As(III) sorption capacities, utilizing the effects of solid:solution ratios and reaction kinetics. Results showed that both WTRs exhibited high affinities for soluble As(V) and As(III), exhibiting Freundlich type adsorption with no obvious plateau after 2-d of reaction (15000 mg kg-1). The Al-WTR was highly effective in removing both As(V) and As(III), although As(III) removal was much slower. The Fe-WTR showed greater affinity for As(III) than for As(V) and reached As(III) sorption capacity levels similar to those obtained with the Al-WTR-As(V) system (15000 mg kg-1). Arsenic sorption kinetics were biphasic, similar to what has been observed with P sorption by the WTRs. Minimal (<3%) desorption of sorbed As(III) and As(V) was observed, using phosphate as the desorbing ligand. Dissolved Fe2+ concentrations measured during As(III) sorption were significantly correlated (r2=0.74, p<0.005) with the amount of As(III) sorbed by the Fe-WTR. Lack of correlation between Fe2+ in solution and sorbed As(V) (r2=0.2) suggests reductive dissolution of the Fe-WTR mediating As(III) sorption. Results show promising potential for the WTRs in irreversibly retaining As(V) and As(III) that should be further tested in field settings.     

Levels of elements in the surficial estuarine sediments of the Hugli River, northeast India and their environmental implications

The present paper is the first document of a detailed geochemical and mineralogical study of muddy to sandy mud estuarine sediments of the Hugli River collected from five different sites along its course in the coastal areas of West Bengal, northeast India. The present work attempts to establish the status of distribution and environmental implications of 52 elements in the surficial estuarine sediments and their possible sources of derivation. The level of both metallic and non-metallic elements shows a wide range of variation all along the course of the estuary and can be attributed to their differential derivation from the source rocks and differential discharge of untreated effluents originating from industrial, agricultural, aquacultural as well as domestic sewage. The element contents, particularly the heavy metal content in the sediments, are the lowest in the upstream part of the estuary at Diamond Harbor, whereas, these are slightly higher in the intermediate stretch of the estuary at Haldia to highest in the mouth of estuary at Gangasagar. These changes indicate that the metals that are carried from upstream find their ultimate depositional sink at the delta mouth near Gangasagar, where almost all the elements showed elevated values. The majority of the elements have their highest concentrations at Canning, a site within the tidal channel network of the Hugli-Matla drainage basin away from the direct influence of the Hugli River. This site is severely contaminated with huge organic load from domestic sewage, aquaculture, intensive trawling activities and agricultural runoff. Moreover, the site suffers from heavy siltation load causing an almost moribund condition of Matla River at this point. Equi-dimensional quartzo-feldspathic mineral grains are consistent components in the siliciclastic composition of the sediments and their sizes at each station are controlled by respective hydrodynamic conditions. Various flaky minerals (mica, chlorite, hornblende) are also present but show inconsistent patterns of distribution. These flaky minerals remain in suspension for a long time and do not follow the usual law of settling of particles depending on the hydrodynamic regime prevailing in the area. Presented data will serve as a baseline against which future anthropogenic effects may be assessed. A comprehensive account of heavy metal content in sediments from different coastal regions of peninsular India has also been presented for purpose of comparison.     

Tropical Coastal Organisms as Qualitative Indicators of Mercury and Organomercury for Sustainable Use of Living Resources

Organisms sensitive to ambient environment are used as bioindicators in monitoring pollution. The present investigation is designed to measure the extent of mercury and organomercury levels in selective biota of different trophic levels inhabiting in the coastal environment of Sunderban Biosphere Reserve, eastern part of India. The primary objective of this work is to provide baseline data for future environmental quality programme and to ascertain the suitability of these organisms to be used as bioindicator species of pollution. The seagrass (Porterasia coarctata), macrobenthos (polychaetes, gastropods and bivalve molluscs) and pelagic finfishes were collected from sites of different physiochemical characteristics. Concentration of total mercury was determined by cold vapour atomic absorption spectrophotometry technique (CVAAS) using a Perkin-Elmer 2380 AAS equipped with MHS 10.Both mercury and organomercury levels showed considerable interspecific and regional variations which reflected the feeding strategy of these animals and also the location of stations. The bivalve molluscs showed a high degree of organ-specificity in accumulation which might be attributed to the ion exchange activity of mucous membrane covering gill and mantle. Mercury levels in various compartments did not reveal any regular temporal variations but showed a slight increase in the late monsoon months indicating the apparent influence of river run-off and reduction in salinity in the ambient medium. A continuous monitoring programme is recommended in order to clarify the present trend and to establish the studied organisms as indicator species.     

A comparative study on cost analysis,efficiency, and process mechanism of effluent treatment plants in Bangladesh

Investigations were conducted into the treatment of effluents produced during manufacturing processes at both a chemicals production facility and a paint manufacturing facility. A comparison of costs of wastewater treatment at both facilities was also performed. The untreated effluents from both facilities were high in biological oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS). In addition, the effluents from the two facilities deviated significantly in dissolved oxygen (DO) content and pH levels. However, both facilities ultimately released treated wastewater with allowable amounts or levels of BOD, COD, TDS, DO, and pH as permitted by the Department of the Environment, Ministry of Environment and Forests, Bangladesh (DOE). The effluent treatment plants (ETP) at both facilities contained combinations of chemical and biological treatment processes. The treatment processes used at the chemicals production facility and at the paint manufacturing facility were continuous and semi‐batch processes, respectively. The biological treatment section of the ETP at the chemicals production facility has both anaerobic and aerobic units, while the paint manufacturing facility has only an aerobic unit. Annual installation and operation costs of the ETP at the chemicals production facility was Bangladeshi Taka (Tk) 1,300,000 ($16,667 US dollars) and Tk 800,000 ($10,257), respectively. The annual installation and operation costs of the ETP at the paint manufacturing facility were Tk 3,050,000 ($39,103) and Tk 6,200,000 ($79,488), respectively.     

Occurrence, distribution and possible sources of organochlorine pesticide residues in tropical coastal environment of India: an overview

Organochlorine pesticides (OCPs) are an important potential component of chemical pollutants used extensively for agriculture and sanitation purposes in India as these are comparatively cheap and effective. These persistent organic compounds such as HCH isomers, DDT and its metabolites are the predominant chemical contaminants found along the Indian coast and thus constitute both alluring and grave areas of scientific research. Our objective in the paper is to provide a comprehensive account of the distribution of organochlorine pesticides in biotic and abiotic compartments of the Indian coastal environment, make some comments on their environmental sources, their movement through the food chain and possible ecotoxicological risk of health in biota including humans. The prevalent HCH, DDT and HCB concentrations differ markedly in eastern and western coast of India reflecting differing agricultural and other usage and their ultimate input into the coastal environment by several rivers and the bioturbation activities of macrozoobenthos (bivalve mollusks, polychaetous annelids, etc.). In several cases, the DDT levels exceeded the effects range-low (ER-L) and could thus cause acute biological impairments, in comparison with the sediment quality guidelines. Contributions of DDT metabolites (DDT, DDD and DDE residues) vary in different Indian coastal regions predominated by pp'-DDT and pp'-DDD. Measured concentrations of HCHs were lower than DDTs that might be due to higher water solubility, vapor pressure and biodegradability of the latter. HCH and DDT residues in fish in India were lower than those in the temperate countries indicating a lower accumulation in tropical fish, which might be related to rapid volatilization of this insecticide in the tropical environment. The concentrations of other chlorinated pesticides (aldrin, dieldrin, eldrin, methoxychlor, endosulfan sulphate) were lower and not generally of great concern.     

Bioremediation of petroleum hydrocarbons in contaminated soils: comparison of biosolids addition, carbon supplementation, and monitored natural attenuation

Two methods of biostimulation were compared in a laboratory incubation study with monitored natural attenuation (MNA) for total petroleum hydrocarbon (TPH) degradation in diesel-contaminated Tarpley clay soil with low carbon content. One method utilized rapid-release inorganic fertilizers rich in N and P, and the other used sterilized, slow-release biosolids, which added C in addition to N and P. After 8 weeks of incubation, both biostimulation methods degraded approximately 96% of TPH compared to MNA, which degraded 93.8%. However, in the first week of incubation, biosolids-amended soils showed a linear two orders of magnitude increase in microbial population compared to MNA, whereas, in the fertilizer-amended soils, only a one order of magnitude increase was noted. In the following weeks, microbial population in the fertilizer-amended soils dropped appreciably, suggesting a toxic effect owing to fertilizer-induced acidity and/or NH(3) overdosing. Results suggest that biosolids addition is a more effective soil amendment method for biostimulation than the commonly practiced inorganic fertilizer application, because of the abilities of biosolids to supplement carbon. No statistically significant difference was observed between the biostimulation methods and MNA, suggesting that MNA can be a viable remediation strategy in certain soils with high native microbial population.     

Effect of water regimes and organic matters on transport of arsenic in summer rice （Oryza sativa L.）

The arsenic contamination in soil-water-plant systems is a major concern of where, the groundwater is being contaminated with arsenic (above 0.01 mg/L) in the Indian subcontinent. The study was conducted with organic matter to find out the reducing e ect on arsenic load to rice (cv. Khitish). It was observed that intermittent ponding reduced arsenic uptake (23.33% in root, 13.84% in shoot and 19.84% in leaf) at panicle initiation stage, instead of continuous ponding. A decreasing trend of arsenic accumulation (root > straw > husk > whole grain > milled grain) was observed in di erent plant parts at harvest. Combined applications of lathyrus + vermicompost + poultry manure reduced arsenic transport in plant parts (root, straw, husk, whole grains and milled grain) which was significantly at par (p > 0.05) with chopped rice straw (5 tons/ha ) + lathyrus green manuring (5 tons/ha) in comparison to control and corresponding soils. A significant negative correlation of arsenic with phosphorus (grain P with arsenic in di erent parts R2= 0.627–0.726 at p > 0.01) was observed. Similarly, soil arsenic had a negative correlation with soil available phosphorus (R2 = 0.822 at p > 0.001) followed by soil nitrogen (R2= 0.762 at p > 0.01) and soil potassium (R2 = 0.626 at p > 0.01). Hence, e ective management of contaminated irrigation water along with organic matter could reduce the arsenic build up to plants and soil.     

Effect of soil properties on arsenic fractionation and bioaccessibility in cattle and sheep dipping vat sites

Historical use of high arsenic (As) concentrations in cattle/sheep dipping vat sites to treat ticks has resulted in severe contamination of soil and groundwater with this Group-A human carcinogen. In the absence of a universally applicable soil As bioaccessibility model, baseline risk assessment studies have traditionally used the extremely conservative estimate of 100% soil As bioaccessibility. Several in-vitro, as well as, in-vivo animal studies suggest that As bioaccessibility in soil can be lower than that in water. Arsenic in soils exists in several geochemical forms with varying degree of dissolution in the human digestive system, and thus, with highly varying As bioaccessibility. Earlier batch incubation studies with As-spiked soils have shown that As bioaccessibility is a function of soil physicochemical properties. We selected 12 dipping vat soils collected from USA and Australia to test the hypothesis that soil properties exert a significant effect on As bioaccessibility in As-contaminated sites. The 12 soils varied widely in terms of soil physico-chemical properties. They were subject to an As sequential fractionation scheme and two in-vitro tests (IVGS and IVGIA) to simulate soil As bioavailability in the human gastrointestinal system. Sequential As fractionation results showed that the majority of the As measured in the dipping vat soils resided either in the Fe/Al hydroxide fraction, or the Ca/Mg fractions, or in the residual fraction. Water-extractable As fraction of the 12 soils was typically <10% of the total, reaching values up to 23%, indicating minimal leaching potential, and hence, lower risk of As-contamination from exposure to groundwater, typically used as drinking water in many parts of the world. Partial individual correlations and subsequent multiple regression analyses suggested that the most significant soil factors influencing As bioaccessibility were total Ca+Mg, total P, clay content and EC. Collectively, these soil properties were able to explain 85 and 86% of the variability associated with the prediction of bioaccessible As, using IVGS and IVGIA in-vitro tests, respectively. This study showed that specific soil properties influenced the magnitude of soil As bioaccessibility, which was typically much lower than total soil-As concentrations, challenging the traditional risk assessment guideline, which assumes that soil As is 100% bioaccessible. Our study showed that total soil As concentration is unlikely to provide an accurate estimate of human health risk from exposure to dipping vat site soils.