This study aimed to evaluate the effect of ,exogenous enzymes (ExE) on feeding behaviour, feed intake, nutrient digestibility and rumen disappearance rate of Holstein cows, as well as methane production from faeces of these cows by means of anaerobic digestion. Five cannulated Holstein cows were distributed in a 5 × 5 Latin square design (5 periods of 21 days each) and received five treatments which differed in inclusion of different ExE in the diet (control: diet without enzymes,amylase: basal diet with 7. 5 g of amylase/cow/day,xylanase: basal diet with 15 g of xylanase/cow/day,cellulase + protease: basal diet with 7. 5 g cellulase + protease/cow/day,and pool: basal diet with 30 g enzyme mixture (all enzymes added at the same dose of individual treatments). Therefore, feeding behaviour, dry matter intake (DMI), nutrient digestibility and rumen disappearance rate were evaluated. Representative pools of faeces from each cow were collected in each period to perform anaerobic digestion. Afterwards, 25 experimental batch-type biodigesters were filled with faece substrates and were subsequently arranged in a completely randomised design of 5 treatments with 5 replicates. Then, evaluations of total gas, methane production, total solid (TS) and volatile solid (VS) removal efficiency were performed. No effect of ExE was observed (P>0. 05) on feeding behaviour (number of daily meals,total daily time spent eating, ruminating or masticating), DMI, nutrient digestibility (although enzyme pool and cellulase + protease tended to increase crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility) or on rumen disappearance rate. No effect of ExE was observed on total gas and methane production or on the efficiency of removal of TS and VS from faeces.  , Exogenous enzymes did not increase efficiency of nutrient utilisation by the animals and, accordingly, did not affect the potential of methane emission from faeces of Holstein cows by means of anaerobic digestion.

Feasibility of methanolic wastes treatment containing chlorophenol in experimental UASB reactors i.e. R-I and R-II working side by side constantly for a couple of almost 32 weeks were studied. UASB reactor R-I was initiated by utilizing the digested sludge alone, whereas, the UASB reactor R-II was startedup by adding an activated carbon of an effective size 1.5-2.5mm to the digested sludge with the volume-volume ratio of 3:2. At low loading rates d” 0.5g-TOC/L-d for R-I and d” 2.6g-TOC/L-d for R-II, it was observed that the effect of HRT on the TOC reduction was not prominent, and in both the reactors the TOC reduction effectiveness was noticed to be above 80%. An optimum OLR to accomplish 80-85% TOC and chlorophenol reduction effectiveness (at HRT e” 12hours) was observed to be 2.6g-TOC/L-day and 10.8g-TOC/L-day for reactor R-I and R-II, respectively. It was also observed that to attain more than 80% TOC removal efficiency at a constant OLR of 6.5g-TOC/L-day and at a HRT of 18-20hours, the maximum influent chlorophenol concentration should stay below 21mg/L and 29mg/L for reactor R-I and R-II, respectively. The average VFAs effluent concentration observed was 357mg/L and 230mg/L for the reactor R-I and R-II, respectively. Comparatively the production of biogas in reactor R-II was less. The overall gas conversation rate observed at greater than 80% TOC removal efficiency for R-I and R-II was found to be 0.28L/g-CODremoved and 0.17L/g- CODremoved, respectively, with 60-62% of methane content for both the reactors. The results of this study suggested that the use of methanol as a medium to biodegrade chlorophenol in the presence of an activated carbon in a UASB reactor is an effective and feasible method at mesophilic temperature and neutral pH.

Two UASB reactors R-I and R-II, each of 10liters capacity, made up of acryl material were operated parallel and continuously for a period of 220 days, using actual effluent of the NSSC pulp and paper mill, at mesophilic temperature and neutral pH. The main objective was to investigate the treatability performance of the reactors at varying OLR and HRT in terms of TOC and lignin removal. The reactor R-I was used by conventional procedure, whereas, for the reactor R-II methanol and activated carbon was added to supplement its efficiency. Corresponding to an optimum OLR of 4.5kg/m3-day and HRT of 18hrs, the reactor R-II gives 69% TOC and 60% lignin removal. But, in the reactor R-I at same operating conditions, only 56% TOC and 51% lignin removal was noticed. However, the biogas yield in the reactor R-I was noticed relatively more than in the R-II. The biogas yield observed was 0.28m3/kg-CODrem and 0.18m3/kg-CODrem in the reactor R-I and R-II, respectively, with 56-58% methane content in both the reactors. The average VFAs concentration observed in the reactor R-I and R-II is 360mg/L and 230mg/L, respectively. The results of this study suggest that the use of methanol and activated carbon to enhance the treatability efficiency of the UASB reactor is a viable option for the treatment of NSSC pulping effluent.

A study of the biokinetics of anaerobic digestion of municipal solid waste (MSW) was carried out using anaerobic batch digester. From the experimental results, the kinetic parameters (coefficient values) of the digestion of the MSW were determined. The maximum rate of substrate utilization (K), saturation constant (Ks), endogenous decay coefficient (Kd), biomass Yield or microbial growth yield (Y) and maximum specific growth rate (mmax) were found to be 0.144 day-1, 21.23 mg/L, 0.038 day-1, 0.367, and 0.053 day-1 respectively. These values indicate that practical digesters for MSW will require inoculation of the feed with microorganism to increase the rate of digestion. The biokinetics of anaerobic digestion of MSW was well described by first order kinetic model.

A structured mathematical model of anaerobic conversion of complex organic materials in non-ideally cyclic-batch reactors for Biogas production has been developed. The model is based on multiple-reaction stoichiometry (enzymatic hydrolysis, acidogenesis, acetogenesis and methanogenesis), microbial growth kinetics, conventional material balances in the liquid and gas phases for a cyclic-batch reactor, liquid-gas interactions, liquid phase equilibrium reactions and a simple mixing model which considers the reactor volume in two separate sections: the flow-through and the retention regions. The dynamic model describes the effects of reactant s distribution resulting from the mixing conditions, time interval of feeding, hydraulic retention time and mixing parameters on the process performance. The model is applied in the simulation of anaerobic digestion of cattle manure under different operating conditions. The model is compared with experimental data and good correlations are obtained.