Basheshwar Prasad

Pretreatment of petrochemical wastewater by coagulation and flocculation and the sludge characteristics

In the present study, coagulation-flocculation was investigated as a pretreatment process for the treatment of purified terephthalic acid (PTA) wastewater. The effect of various inorganic and organic coagulants on the treatment of wastewater collected from flow equalization tank of an effluent treatment plant was studied. The settling and filtration characteristics of the sludge were also studied. The jar tests revealed that the wastewater was best treated when 3000 mg l(-1) of ferric chloride was dosed at pH 5.6. At optimum conditions, COD of the wastewater was reduced by 75.5%. The results of the gravity filtration of the treated wastewater showed that the addition of cationic polyacrylamide (175 mg l(-1)) to ferric chloride coagulation improved the filtration characteristics and reduced the specific cake resistance. Scanning electron microscopy and energy dispersive spectroscopy studies were also conducted to know the sludge structure and composition, respectively. Thermal analysis of the sludge showed that the oxidation of the sludges in the present study is a three step process. However, with the addition of C-PAA to ferric chloride coagulation system, the oxidation was found to be a two step process.

Isotherm and kinetics study for acrylic acid removal using powdered activated carbon.

The potential of powdered activated carbon (PAC) for the adsorption of acrylic acid (AA) from aqueous solution was studied at the initial concentration (C(0)) in the range of 50-500 mg/l over the temperature range of 303-348 K. The equilibrium adsorption studies were carried out to evaluate the effect of adsorbent dosage and contact time, change in pH by adding adsorbents and the initial concentration. Langmuir, Freundlich and Redlich-Peterson (R-P) equilibrium isotherm models were tested to represent the data. Error functions were used to test their validity to fit of the adsorption data with the isotherm and kinetic models. The Freundlich isotherm equation is found to best represent the equilibrium separation data in the temperature range of 303-348 K. The maximum adsorption capacity of AA onto PAC was obtained as q(m)=36.23 mg/g with an optimum PAC dosage w=20 g/l at 303 K for C(0)=100 mg/l. The pseudo-second-order kinetics is found to represent the experimental AA-PAC data. The negative value of DeltaG(ad)(o) (-16.60 to -18.18 kJ/mol K) indicate the feasibility and spontaneity of the adsorption process.

Biomass Residue Briquetting and Characterization

All kinds of biomasses pull carbon out of the air as they grow. Waste biomass can be made into usable fuel by densification. These biomasses can then replace some coal in power plants, which will reduce carbon emissions and greenhouse gas effects. Densification of low-density biomass (agricultural and agro-industrial waste) is called biomass briquetting. The briquette form facilitates easy transportation, enables better handling and storage, and is efficient to use as an alternative fuel to coal and firewood. The high temperature developed during the high-pressure densification process assists the inherent lignin, which is the binder in the biomass, to bind the biomass and form a densified fuel called briquettes. In this paper, four kinds of biomasses (mango leaves, eucalyptus leaves, wheat straw, and sawdust) were briquetted. Physicochemical and thermochemical characterization of the biomass residues was carried out by using standard methods. A hydraulic press and an automatic compression testing machine were used for the briquetting and testing. The effect of various parameters, such as compression pressure, pressure application rate, holding time, particle size, and moisture content, on the density of the briquettes was studied. The impact resistance test was carried out by using the standard ASTM method. All the briquettes prepared from the biomass studied in this paper have more heating value than half of Indian coal; thus, they can be used as an alternative to coal and firewood.

On the kinetics and effectiveness of immobilized whole-cell batch cultures

Abstract A model for growth-associated fermentations is presented for batch cultures of immobilized whole cells. The model encompasses exponential and steady-state growth phases and the effectiveness of the biocatalyst. Based on the model equations, experimental methods have been developed for the determination of the kinetic parameters: maximum specific growth rate (μ max ), Monod constant ( K m ) and effectiveness factor (η). These methods are illustrated by ethanol fermentations using Saccharomyces cerevisiae cells entrapped in alginate beads. The kinetic parameters obtained show consistency with those determined for free-cell systems.

Treatment of desizing wastewater by catalytic thermal treatment and coagulation.

In the present study, the coagulation of the fresh and thermally treated desizing wastewater has been reported. The maximum COD reduction of fresh desizing wastewater using coagulation was observed with commercial alum at initial pH 4. This was followed by aluminum potassium sulfate (pH 4), FeCl(3) (pH 6), PAC (pH 6) and FeSO(4) (pH 4). The maximum COD reduction observed at a coagulant (commercial alum) dose of 5 kg/m(3) and pH 4 was 58% whereas the color reduction at these conditions was 85%. The results reveal that the application of coagulation on the catalytic thermal treated effluent is more effective in removing nearly 88% of COD and 96% of color at above mentioned conditions except at a coagulant dose of 1 kg/m(3). The amount of inorganic sludge generated gets drastically reduced (almost 25%) due to the reduced amount of coagulant. The COD and color of the final effluent were found to be 98.6 mg/l and 2.67 PCU, respectively, and the COD/BOD(3) ratio was 1.36. The settling rate of the slurry was found to be strongly influenced by treatment pH. The slurry obtained after treatment at pH 12 settled faster in comparison to slurry obtained at pH 4. The filterability of the treated effluent is also strongly dependent on pH. pH 12 was adjudged to be the best in giving highest filtration rate.

Catalytic cracking of jatropha-derived fast pyrolysis oils with VGO and their NMR characterization

Lignocellulosic biomass-derived fast pyrolysis oils are potential second-generation bio-fuels towards the reduction of greenhouse gas (GHG) emissions and carbon foot prints. This study pertains to co-process the Jatropha-derived heavy or tar fraction of fast pyrolysis oil (FPO) with vacuum gas oil (VGO) and hydrodeoxygenated fast pyrolysis oil (HDO) with VGO in a standard refinery fluid catalytic cracking (FCC) unit. The crude fast pyrolysis oil from Jatropha curcas is produced at 530 °C and atmospheric pressure using a bubbling fluidized bed pyrolyzer. The heavy fraction of FPO is hydrodeoxygenated over Pd/Al2O3 catalyst into HDO in an autoclave reactor at 300 °C and pressure of 80 bar. Further, HDO is co-processed with petroleum-derived VGO in an advanced cracking evaluation (ACE-R) unit to convert it into refinery FCC product slate hydrocarbons at a blending ratio of 5 : 95. FPO and HDO are characterized using 31P NMR, whereas FCC distillates, which are obtained on the co-processing of VGO with fast pyrolysis oil and HDO, are characterized using 1H and 13C NMR spectroscopy techniques. The 31P NMR analysis of crude FPO and HDO indicated that hydroxyl, carboxylic and methoxy groups are reduced during the hydrodeoxygenation of FPO. The experimental results at the iso-conversion level on the co-processing of HDO with VGO indicated a higher yield of liquefied petroleum gases (LPG), while lower yields of gasoline and LCO have been observed as compared to FPO co-processing with VGO and co-processing of pure VGO. Furthermore, the results of co-processing of FPO with VGO indicated that the yields of gasoline and LCO increased from 29 to 35 wt% and 14.8 to 20.4 wt%, respectively, whereas the yields of dry gas and LPG decreased from 2.1 to 1.4 wt% and 38.8 to 23.7 wt%, respectively, for an increase in the blending ratio from 5% to 20%. Therefore, it can be concluded that the co-processing of HDO with VGO in a FCC unit would be feasible in order to achieve a higher yield of LPG.

Treatment of Petrochemical Wastewater by Acid Precipitation and Carbon Adsorption

AbstractThis paper deals with the physicochemical treatment of petrochemical wastewater emanating from a purified terephthalic acid (PTA) manufacturing unit. The PTA wastewater has a very high chemical-oxygen demand (COD=3,530  mg·dm−3) and contains various acids like terephthalic acid (TA), benzoic acid (BA), acetic acid, and p-toluic acid (p−TA), in addition to aldehydes. The treatment of this wastewater with 1 N sulfuric acid (pH 2.0) at 25°C resulted in the removal of 53.2% of the COD, >90% of TA, and >60% of BA in the form of solid precipitate. Subsequent treatment of the clear supernatant with granular activated carbon (GAC) resulted in an overall removal of >99% of TA and BA in addition to 82.7% of the COD. The GAC is basic in nature with its pH at the point of zero charge being 8.3. It was also predominantly microporous with a BET surface area of 134.69  m2·g−1. Fourier-transform infrared spectroscopy of the GAC, before and after the adsorption of PTA wastewater components, was carried out to unde...

Continuous electrocoagulation treatment of pulp and paper mill wastewater: operating cost and sludge study

The present research deals with the treatment of agri-based pulp and paper mill wastewater by continuous electrocoagulation (CEC) process using iron (Fe) as an electrode material. Effects of flow rates (dm3 h−1): 0.5–4.0 and residence time (τ): 0.5–4.0 h were investigated on degradation of chemical oxygen demand (COD), color, total solid (TS), turbidity, specific energy consumption (SEC), instantaneous current efficiency (ICE) and electrochemical degradation index (EDI). At flow rates of 1.0 and 0.5 dm3 h−1, COD removal efficiency of 78.20 and 82.15%; and color removal efficiency of 79 and 90%, respectively, was achieved. TS concentration of wastewater slurry was also reduced by 65% after 3 h residence time with flow rate of 1 dm3 h−1. The specific energy consumption (kW h per kgCODremoved) was decreased from 16.3 to 14.3 with decrease in τ from 4 to 1 h. At a supply charge concentration of 0.62 A h dm−3, the current efficiency (CE) values were 310% and 274% after τ = 2 and 1 h, respectively. Dissolution and consumption of electrodes were also studied with a change in flow rates. Sludge obtained after the CEC process was analyzed for settling and filterability characteristics, morphology and elemental analysis, point of zero charge, physicochemical and elemental characterization, and TS concentration. The operating cost of the process was also calculated based on the electrical energy and electrode consumption and was found to be 61.0 Indian Rupees (0.9 USD) for the treatment of 1 m3 of wastewater.

Adsorption Kinetics and Thermodynamics of COD Removal of Acid Pre-treated Petrochemical Wastewater by using Granular Activated Carbon

Granular activated carbon (GAC) was used as adsorbent in batch experiments for the removal of COD from Purified Terephthalic Acid (PTA) wastewater. The results showed that COD adsorption onto GAC follows pseudo-second-order rate kinetics and that both boundary-layer diffusion and intraparticle diffusion are likely involved in the rate-limiting mechanisms. The adsorption of PTA wastewater components (COD) onto GAC was found to be exothermic. ΔH° value is −18.34 kJ/ mol indicating the complexity of the adsorption which is neither completely physical nor chemical in nature. The energetically heterogenic nature of the GAC surface was depicted by the variation in ΔHst,a with the surface loading.

Physicochemical and thermal characteristics of the sludge produced after thermochemical treatment of petrochemical wastewater

The present work describes the physicochemical and thermal characteristics of the sludge generated after thermochemical treatment of wastewater from a petrochemical plant manufacturing purified terephthalic acid (PTA). Although FeCl3 was found to be more effective than CuSO4 in removing COD from wastewater, the settling and filtration characteristics of FeCl3 sludge were poorer. Addition of cationic polyacrylamide (CPAA; 0.050 kg/m3) to the FeCl3 wastewater system greatly improved the values of the filter characteristics of specific cake resistance (1.2×108 m/kg) and resistance of filter medium (9.9×108 m−1) from the earlier values of 1.9×109 m/kg and 1.7×108 m−1, respectively. SEM-EDAX and FTIR studies were undertaken, to understand the sludge structure and composition, respectively. The moisture distribution in the CuSO4 sludge, FeCl3 sludge and FeCl3+CPAA sludge showed that the amount of bound water content in the CuSO4 and FeCl3+CPAA sludges is less than that of the FeCl3 sludge and there was a significant reduction in the solid–water bond strength of FeCl3+CPAA sludge, which was responsible for better settling and filtration characteristics. Due to the hazardous nature of the sludge, land application is not a possible route of disposal. The thermal degradation behaviour of the sludge was studied for its possible use as a co-fuel. The studies showed that degradation behaviour of the sludge was exothermic in nature. Because of the exothermic nature of the sludge, it can be used in making fuel briquettes or it can be disposed of via wet air oxidation.