Puspendu Bhunia

A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters

Textile industry is one of the most chemically intensive industries on the earth and the major polluter of potable water. It generates huge quantities of complex chemical substances as a part of unused materials including dyes in the form of wastewater during various stages of textile processing. The direct discharge of this wastewater into environment affects its ecological status by causing various undesirable changes. As environmental protection becomes a global concern, industries are finding novel solutions for developing technologies that can diminish the environmental damage. However, colour removal from textile wastewater by means of cheaper and environmental friendly technologies is still a major challenge. In this manuscript, several options of decolourisation of textile wastewater by chemical means have been reviewed. Based on the present review, some novel pre-hydrolysed coagulants such as Polyaluminium chloride (PACl), Polyaluminium ferric chloride (PAFCl), Polyferrous sulphate (PFS) and Polyferric chloride (PFCl) have been found to be more effective and suggested for decolourisation of the textile wastewater. Moreover, use of natural coagulants for textile wastewater treatment has also been emphasised and encouraged as the viable alternative because of their eco-friendly nature.

Ultrasonic pretreatment of sludge: A review

Ultrasonication is an emerging and very effective mechanical pretreatment method to enhance the biodegradability of the sludge, and it would be very useful to all wastewater treatment plants in treating and disposing sewage sludge. Ultrasonication enhances the sludge digestibility by disrupting the physical, chemical and biological properties of the sludge. The degree of disintegration depends on the sonication parameters and also on sludge characteristics, therefore the evaluation of the optimum parameters varies with the type of sonicater and sludge to be treated. The full-scale installations of ultrasonication have demonstrated that there is 50% increase in the biogas generation, and in addition evaluation of energy balance showed that the average ratio of the net energy gain to electric consumed by the ultrasound device is 2.5. This review article summarizes the benefits of ultrasonication of sludge, the effect of sonication parameters, impact of sludge characteristics on sludge disintegration, and thereby the increase in biogas production in anaerobic digester. Due to uncertainty in the unit representation by many researchers and nonavailability of the data, comparison of these results is complicated. Comparison of ultrasonication with other pretreatment options is necessary to evaluate the best economical and environmental pretreatment technology for sludge treatment and disposal. The optimum parameters for the ultrasonication vary with sludge characteristics.

A mechanistic approach to evaluate the effectiveness of red soil as a natural adsorbent for phosphate removal from wastewater

AbstractThe present study was conducted to investigate the efficacy of red soil (RS), as a natural adsorbent, for phosphate removal from wastewater. The chemical composition of the adsorbent was determined by proton-induced X-ray emission and proton-induced γ-ray emission methods. Apart from evaluating the influence of major experimental parameters, the equilibrium data were analyzed by different isotherm models and kinetic models. Experimentally obtained values, such as separation factor (RL), 0.0297, Freundlich exponent (n), 2.994, and Gibb’s free energy change (ΔG°), −1.279 kJ mol−1, suggest that the phosphate adsorption by RS was a favorable and spontaneous process. The presence of coexisting anions showed no competing effects on phosphate removal efficiency. For synthetic initial phosphate concentration of 20 mg L−1 and contact time of 90 min, phosphate removal efficiency was 96.47% in batch mode and 19 h of breakthrough time in column mode. Whereas with real domestic wastewater having 5.62 mg L−1 of...

Simultaneous removal of nitrogen and phosphorous from domestic wastewater using Bacillus cereus GS-5 strain exhibiting heterotrophic nitrification, aerobic denitrification and denitrifying phosphorous removal

A newly isolated GS-5 strain exhibiting heterotrophic nitrification, aerobic denitrification and denitrifying phosphorous removal was identified as Bacillus cereus GS-5 based on its phenotypic and phylogenetic characteristics. The isolate had exhibited efficient NH4+-N, NO3--N, NO2--N and PO43--P removal from nutrient spiked real domestic wastewater with average rates of 2.62, 2.69, 1.16 and 0.42mgL-1h-1, respectively under aerobic condition. Metabolic inhibitor based mass balance analysis indicated that dinitrogen gas (41%), intracellular nitrogen (29%) and intracellular phosphorous (60%) were the major fates of the initial NH4+-N and PO43--P. The successfully expression of hydroxylamine oxidase (hao), nitrate reductase (nar), nitrite reductase (nir) and poly phosphate kinase (ppk) enzyme in the cell free extracts and PCR amplification of nar, nir and ppk genes in the isolated strain provided further evidences for the nutrient removal possibility. A possible pathway of for nitrogen removal by GS-5 is suggested.

Fundamentals of Biological Treatment

This chapter provides important information on the fundamentals and engineering aspects of biological wastewater treatment. Understanding the behavior of the naturally occurring microorganisms and their biochemical reactions plays a vital role in the successful design and operation of biological wastewater treatment plants. With proper analysis and design, almost all wastewaters containing biodegradable organics can be treated biologically. The main objectives of this chapter are to (1) give an overview of the biochemical reactions, (2) classify the different types of microorganisms, (3) establish different aspects of microbial metabolism, (4) understand the stoichiometry and energetics of bacterial growth, (5) establish comprehension of the bacterial growth kinetics, and (6) to introduce the role of environmental factors influencing the different biological processes. The methods used to describe and solve the problems presented are those used by biochemical engineers, based on mass balances that are valid for specific systems.

A mechanistic review on vermifiltration of wastewater: Design, operation and performance

With global population explosion, the available water resources are slowly being polluted due to the excessive human interference. To encounter this, it is the need of this hour to find out sustainable pollution remediating technologies to meet the stringent discharge standards for domestic as well as industrial wastewaters. In addition, those techniques should have the capabilities for effective implementation even in developing countries. Based on the available literatures, one such technique, named vermifilter, has been identified which takes care of almost all the sustainable and economical criteria for its effective implementation even in developing countries. The aim of this meta-analysis is to provide a comprehensive review on assessment mechanisms involved, factors affecting the process and performance of vermifiltration under different scenarios. The present review envisages the current state of the knowledge regarding physical, chemical and biological aspects related to the treatment mechanisms and effective functioning of earthworms. This review has also proposed several suggestive plans on its application at any proposed site.

Supremacy of Magnesium Chloride for Decolourisation of Textile Wastewater: A Comparative Study on the Use of Different Coagulants

In this study, treatment efficiency of magnesium chloride (MgCl2.6H2O) was compared with respect to ferrous sulphate (FeSO4.7H2O), polyaluminium chloride (PACl), and aluminium chlorohydrate (ACH) for the treatment of textile wastewater. Treatment efficiency was assessed in terms of decolourisation and chemical oxygen demand (COD) reduction of synthetic textile wastewater containing reactive, direct and disperse dyes, along with the other chemical constituents that are normally released from different textile processing units. MgCl2.6H2O/Lime produced colour removal efficiency of 99.68% at a dosage 1200mg/L for the wastewater containing all the three dyes together. MgCl2.6H2O/Lime was also found to be the most effective coagulant system for treatment of textile wastewater containing only reactive dye, which produced 99.73% colour removal at a dosage of 1100 mg/L. For both the direct and disperse dyes, ACH was found to be superior over MgCl2.6H2O/Lime, FeSO4.7H2O/Lime, and PACl. Industrial grade ACH, which is normally used as polyelectrolyte, for the first time was used as coagulant in this study and was also appeared to be significant for decolourisation of textile wastewater containing all the three dyes together. From this study, MgCl2.6H2O/Lime was recommended as the best coagulant for the decolourisation of textile wastewater having very high original pH.

Development of an integrated system for the treatment of rural domestic wastewater: emphasis on nutrient removal

With the aim of enhancing the nutrient removal from rural domestic wastewater while reducing the cost of the treatment process, a novel, integrated treatment system consisting of a multi-stage bio-filter with drop aeration and a post positioned attached growth carbonaceous denitrifying bio-reactor was designed and developed in this study. The bio-filter was packed with ‘dolochar’, a sponge iron industry waste, as an adsorbent mainly for phosphate removal through a physicochemical approach. The denitrifying bio-reactor was packed with many waste organic solid substances (WOSS) as carbon sources and substrates for biomass attachment, mainly to remove nitrate in the biological denitrification process. The performance of the modular system, treating real domestic wastewater was monitored for a period of about 60 days and the average removal efficiencies during the period were as follows: phosphate, 99.48%; nitrate, 92.44%, ammonia, 96.64%, with mean final effluent concentration of 0.153, 5.5, and 1.06 mg L−1, respectively. This treatment system would allow multipurpose reuse of the final effluent. Moreover, the saturated dolochar can be used as a nutrient supply in agricultural practices and the partially degraded carbonaceous substances can also be used as an organic fertilizer after composting. Thus, the system displays immense potential for treating domestic wastewater significantly by decreasing the concentrations of nutrient and most importantly, facilitating the conversion of the waste materials into usable ones.

Applicability of a new pre-hydrated industrial grade polyaluminium salt for the decolourisation of textile wastewater

AbstractThis study was conducted to assess the decolourisation and chemical oxygen demand (COD) reduction efficiency of a novel pre-hydrated aluminium salt as aluminium chlorohydrate (ACH) for the treatment of textile wastewater using coagulation/flocculation technology. Though, ACH belongs to the same group of polyaluminium salts, it is significantly different from polyaluminium chloride (PACl) in terms of the degree of hydration and alumina content and was used for the first time as a coagulant for the decolourisation of synthetic as well as real textile wastewater. The experimental results revealed that ACH is highly effective for the treatment of synthetic textile wastewater producing more than 99% of colour removal and 45% of COD reduction efficiency at a very low dosage of 200 mg L−1. The decolourisation of real textile wastewater was found to be very much in line with the results obtained for the treatment of synthetic textile wastewater. Superior decolourisation efficiency at a very low dosage as ...

Carbonaceous organics removal kinetics in an upflow anaerobic sludge blanket (UASB) reactor treating physico-chemically pre-treated textile wastewater

In the present study, physico-chemically pre-treated textile wastewater with a residual chemical oxygen demand (COD) of 780 ± 10 mg L �1 was treated using a lab-scale upflow anaerobic sludge blanket (UASB) reactor at variable HRTs of 30.8 to 8 h, and organic loading rates (OLRs) of 0.62‐2.4 kg COD m �3 d �1 . Using a new composite coagulant at dosage of 800 mg L �1 for pre-treatment, more than 99% of colour was removed from the feeding influent to UASB reactor. The optimum OLR was found as 0.95 kg COD m �3 d �1 at which maximum COD reduction (98%) was achieved. Modified Stover-Kincannon, Grau second-order, Monod, Haldane and Contois models were applied to evaluate the carbonaceous substrate removal kinetics inside the UASB reactor. The experimental results of this analysis revealed that modified Stover-Kincannon and Grau second-order kinetics were suitable for predicting the performance and to estimate the kinetic coefficients of UASB reactor.