Volume 20, Issue 6

Acid Mine Drainage (AMD) is one of the persistent water pollution problems in many coal mines of U.S.A. and Canada. Only few mines in India face this problem. The treatment of acid mine water has become a statutory requirement in almost all mines of the world. Metal removal and alkalinity generation is essential feature of any AMD treatment system but sulphate removal from acid mine drainage is still given the secondary importance. In the present study, four AMDs were treated in laboratory Successive Alkalinity Producing System (SAPS) for five different hydraulic retention times (HRT). The total iron removal and corresponding sulphate removal along with net alkalinity generation were studied during AMD treatment process by SAPS. A complete removal of total iron and sulphate removal of over 59% have been achieved. The study revealed that the total iron removal and sulphate removal increases with increase in HRT and its removal exhibited linear relationship. A substantial increase in alkalinity was also found after SAPS treatment. The findings of the study can be utilized in design of SAPS for removal of iron and sulphate during treatment of AMD in mining areas.

Textile and dye industries generate wastewater which is considered as highly polluted and carcinogenic. Due to this, treatment of wastewater is required earlier to discharge or recycle. In the present studies, treatment of dye bearing water (DBW) has been explored. The treatment was performed using activated sludge (mixed culture) for aerobic process in sequential batch reactor (SBR). The fill volume ( V F ) and fill time ( t F ) variation in the treatment of DBW was taken place. The initial value of dye concentration, chemical oxygen demand (COD), sludge, and hydraulic retention time (HRT) were found to play important role in the treatment. At optimum condition (HRT = 2.5 d), the 86.84% COD reduction of 190 mg/L COD, and 92.33% dye reduction of 339 mg/L dye were achieved. These values are equal to overall 94.85% dye reduction of 500 mg/L, and 93.15% COD reduction of 380 mg/L. As a result, 500 mg/L dye was reduced to 26 mg/L, and 380 mg/L COD was reduced to 25 mg/L. The biodegradation fitted to Monod kinetics, for which kinetics parameter values of specific growth rate constant of biomass µ  = 0.0047 h −1 , yield coefficient ( Y ) = 1.059, and substrate utilization rate ( q ) = 0.0044 h −1 were evaluated at HRT = 2.5 d. The results show, this process can be applied to treat Acid Red 3BN Dye Water (AR3BNDW).

Domestic sewage (DS) was first treated in aerobic sequential batch reactor (SBR). In order to increase the treated water quality, DS from SBR was further treated using electrocoagulation (EC) and Ion exchange (IE) process. In the SBR study, process parameters such as hydraulic retention time (HRT) and reactor fill time ( t f ) was optimized at various volume exchange ratio (VER) of 0.534, 0.4, 0.266, and 0.133. The best HRT and t f were observed to be 0.78 day (d) and 2 h, respectively, providing 72.37% chemical oxygen demand (COD) reduction (initial value of COD = 270 mg/dm 3 ). Kinetics of biodegradation in SBR was also studied. The second stage treatment was performed in EC reactor at 1 ampere (A) current for 30 min electrolysis time ( t R ). EC reactor, further reduced COD and biological oxygen demand (BOD) up to 72 and 21 mg/dm 3 from its average initial COD and BOD of 94 and 23 mg/dm 3 , respectively. Second stage treatment in IE process reduced hardness, sulphate, and phosphate up to 15, 0.05, and 0.13 mg/dm 3 from its initial value 350, 5.48 and 1.16 mg/dm 3 , respectively. The treated water can be used as potable water after disinfection as its water quality is near to river water.

The sugar industry effluent (SIE) is characterized as high organic load. The aim of this study is to treat SIE by bio-aerobic process in batch and continuous mode in bio-aeration reactor. In batch process, effect of hydraulic retention time (HRT) in terms of effluent fill volume, and in continuous process, effect of HRT in terms of effluent feed rate was studied. In batch process, HRT of 2.5 d (fill volume = 0.8 dm 3 ) was found to be the best and in continuous process, HRT of 1.37 d (feed rate = 133 mL/h) was found to be the best. The chemical oxygen demand (COD) reduction by bio oxidation followed first order kinetics with respect to COD and the rate constant (K) was evaluated as 5.197 d −1 . The sludge yield coefficient (a) and sludge endogenous oxidation coefficient (b) were also evaluated from sludge formation studies, which are 0.4 (gm VSS produced/g COD removed) and 0.1 (g VSS oxidized/day. g MLVSS in the aeration basin), respectively. In continuous process, the COD reduction of 83.12% of 4800 mg/dm 3 and BOD reduction of 88.70% of 1240 mg/dm 3 were obtained at HRT = 1.37 d. The results of the experiments show the SBR process to be an effective process for the treatment of SIE.

Wastewater generated from the coking processes has high load of organic as well as inorganic pollutants which requires the application of effective treatment techniques. In the present work, treatment of coking wastewater (CWW) through catalytic thermolysis has been carried out in batch mode with varying parameters such as type of catalyst, catalyst mass loading, pH, temperature and time. This process was followed by adsorption as second stage treatment process. The final parameters obtained are as Chemical Oxygen Demand (COD) 20 mg/L, cyanide 0.42 mg/L and nil amount of phenol from the high initial organic and inorganic load. The study aims reduction of COD, phenol, and cyanide content in the wastewater to the permissible limits. The mechanism and kinetics of thermolysis process have been also presented in this study.

Polyphosphoric acid (PPA) is widely used in inorganic salt production, petrochemical industry, electronic material preparation and other manufacturing industries. Conventional preparation methods of PPA has disadvantages of pollution, high energy consumption and long production time. To address this problem, microwave continuous-flow preparation may be a desirable way due to its advantages of environmentally-friendly, rapidity and high efficiency. Therefore, to explore the process of preparing PPA by microwave continuous-flow method, a continuous-flow microwave reactor was designed for the dehydration process of orthophosphoric acid to prepare PPA in this paper. The microwave-assisted dehydration process was studied in comparison with the conventional dehydration process and the “closed” microwave-assisted dehydration process in terms of energy efficiency, process times and treatment capacity. The effect of input microwave power, reduced pressure and inlet flow velocity of orthophosphoric acid on the performance of the dehydration process was studied. The results showed that the influence of the microwave power on the temperature rise process during dehydration is greater than that of the reduced pressure. Moreover, the inlet flow rate has a great impact on the treatment capacity and product quality of the dehydration process. Bedsides, the comparison with the other two methods showed that microwave heating can effectively shorten the dehydration time, and the continuous-flow treatment can effectively improve the treatment capacity of microwave heating. The perspectives of the process scale-up by continuous-flow microwave heating method is also discussed.

Slurry polymerization processes using Zeigler–Natta catalysts are most widely used for the production of polyethylene due to their several advantages over other processes. Optimal operating conditions are required to obtain the maximum productivity of the polymer at minimal cost while ensuring operational safety in the slurry phase ethylene polymerization reactors. The main focus of this multi-objective optimization study is to obtain the optimal operating conditions corresponding to the maximization of productivity and yield at a minimal operating cost. The tuned reactor model has been optimized. The single objective optimization (SOO) and multi-objective optimization (MOO) problems are solved using non-dominating sorting genetic algorithm-II (NSGA-II). A complete range of Pareto optimal solutions are obtained to obtain the maximum productivity and polymer yield at different input costs.

Moving towards green technology, alternatives to current detrimental, unsustainable, and expensive energy applications for eco-friendly energy are attracting great attention. Resource recycling and the convenient treatment of animal waste to diminish its nature impact are recently momentous subjects. Microbial fuel cells used cow waste have remarkable potential in electrical energy generation for clean, renewable and sustainable operation. In this study, double-chambered MFC was manufactured using cow manure as raw material at the anode chamber, graphite as the anode and cathode electrodes, fountain water in the cathode chamber, and proton exchange membrane. Because bacteria a catalytic reaction for the latent chemical energy of the cow manure was effectuated as a result of this, MFCs produced electricity. Electricity production performance of this MFC at low temperature (0–10 °C) conditions was examined. This MFC produced a maximum of 204.9 ± 0.1 mV open circuit voltage and 57.387 mW/m 2 power density under low temperature conditions. In particular, the sustainability and applicability of MFCs have been increased thanks to this operation done at low temperatures (0–10 °C).

The effect of particle size on the pressure profiles and flow regimes of the bed containing TiO 2 microparticles (MPs) was investigated in a fluidized bed. The fluidization behavior of particles with mean diameters, d p , of 170, 200, 225, and 300 μm at different gas velocities, U g , was investigated both experimental and computational viewpoints. A computational fluid dynamic (CFD) model was developed by the Eulerian–Eulerian approach to evaluate the sensitivity of the Syamlal–O’Brien, and Gidaspow drag models on the predicted results of the bed pressure profiles. The results showed that with increasing particle size, the amplitude of pressure fluctuations increases and the type of flow regime in the bed tended from bubbling to slugging flow regime. The error analysis showed that the use of the Gidaspow model led to more accurate results than the Syamlal–O’Brien model in predicting the bed pressure drop and pressure fluctuations in the slugging flow regime. However, the Syamlal–O’Brien model was more suitable for predicting the pressure profiles in the bubbling flow regime. The results were more suitable for the bed containing particles of 300 μm than the beds with d p  ≤ 225 μm. The highest and lowest deviations between the experimental data and simulation outputs were obtained at U g of 0.295 and 0.650 m/s, respectively. The findings confirmed that the mutual effects existed between the d p pressure profiles, and the type of flow regimes in the bed.