Volume 15 - 2013

The present study has successfully explored the use of pomegranate seed de-oiled cake as a major additive and micronutrients solution as a minor additive to enhance production of biogas and enrich its methane content, using mango peel as the initial substrate. While micronutrients solution has activated enzymes to carry out anaerobic digestion for optimal production of biogas and methane, pomegranate seed de-oiled cake has (a) provided buffering capacity for stabilized pH/alkalinity:acidity ratio, (b) reduced C:N ratio of the substrates to facilitate anaerobic digestion, cumulatively effecting enhanced biogas generation (0.82 m3 kg-1 VS fed) and its rich methane content (0.64 m3 kg-1 VS fed)

The effect of different operational parameters in UV/TiO2 process, such as initial dye concentration (20-50 mg l-1), light intensity (8-45 W m-2), pH (2.83-10.22), hydrogen peroxide concentration (100-500 mg l-1), temperature (21-45 ˚C) and photocatalyst concentration (150-900 mg l-1) were investigated on the decolorization of Acid Yellow 23 as a model compound from monoazo textile dyes. The apparent first-order rate constants (kap) were evaluated which confirms pseudo first-order kinetics. kap increased with the enhancement of pH, light intensity and temperature. A desired concentration found for hydrogen peroxide (400 mg l-1) and photocatalyst concentration (750 mg l-1). The SnO2 photocatalyst was not as effective as TiO2 but had the same desired concentration (750 mg l-1). Then TiO2+SnO2 suspensions (375+375 mg l-1) as photocatalysts were employed for decolorization at different solution thicknesses. The results showed that the coupled particles were not much different from single TiO2 system at the solution thickness of 4.5 cm in a batch reactor. But the coupled system was more effective when the solution thickness was reduced to 2.5 cm. Over 90% of decolorization occurs at the solution thickness of 1.1 cm after 30 min of irradiation while 90% decolorization takes place at the solution thickness of 4.5 cm after 100 min of irradiation.

In this study, the removal of a cationic dye, basic red 18, used in the textile industry with montmorillonite was investigated as a function of initial dye concentration, pH, agitation speed, adsorbent dosage, ionic strength, and temperature. Adsorption process was attained to the equilibrium within 30 minutes. The adsorption capacity of basic red 18 increased with increasing ionic strength, initial dye concentration, pH, agitation speed, and temperature, but decreased with increasing adsorbent dosage. The experimental data were analyzed by Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich isotherms, and it was found that the isotherm data were reasonably correlated by Freundlich isotherm. Pseudo-first order, pseudo-second order, Elovich kinetic equations and intraparticle diffusion model were used to examine the experimental data of different initial conditions. It was found that the pseudo-second order kinetic equation described the data of dye adsorption onto montmorillonite very well. Furthermore, for the removal of basic red 18, a semi-empirical model was established. Thermodynamic analysis was carried out for basic red 18 onto montmorillonite. It was found that the adsorption processes were endothermic in nature. The values of Ea, ΔH*, ΔS* and ΔG* at 293 K for basic red 18 adsorption on clay were calculated as 27.635 kJ mol-1, 25.041kJ mol-1, -0.090 kJ mol-1 K-1 and 51.412 kJ mol-1, respectively. The results indicated that montmorillonite could be employed as an alternative to commercial adsorbents in wastewater treatment for the removal of color and dyes.

The use of organic manures as amendments to improve soil organic matter level and long term soil fertility and productivity is gaining importance. The disposal of the great quantity of organic wastes produced by the municipal, agricultural and agroindustrial activities, is causing energetic, economic and environmental problems. Sludge composting and using them in agriculture should be a priority for their disposal. Sludge should be treated not as a waste but as a valuable non-farm sources of organic matter to soil. The composting process is a useful method of producing a stabilized material that can be used as a source of nutrients and soil conditioner in fields. The objective of this study was estimation of optimal dose of sewage sludge in composting mixture to obtain of mature and stable compost. The mixture was prepared from sewage sludge (10-40%), organic fraction of MSW(30%), grass (20-50%), sawdust as a bulking agents. Maximum temperature in the bioreactor reached 68.9°C between 1st and 3rd day of composting, and the mean temperature during this period fluctuated from 36 to 46°C. Later, the temperature gradually decreased and after 30 days of composting it approached ambient air temperature which means the end of process. There was significant impact of the high temperature on the rate of the process and of the extent of the hygienisation. The results show that all initial samples are infected with helminth eggs but there is a large variation in the degree of infection for the different sludge samples (102 to 256 eggs kg-1 d.m.). The inactivation of the helminth eggs in the compost can be accomplished, if the temperature inside of the reactor is sufficient as in the case M III and M IV. The final compost M III and M IV was well sanitized as a result of the high temperature achieved due to higher grass addition in those mixtures. Composts M I and M II can not be used in agriculture because of bad microbiological characteristic, however MII can be used for recultivation after hygienisation. The composted material assumed the appearance and structure similar to the so-called horticultural soil. As an exothermic process, composting caused very high loss of water in composted material. All the composts were granular, dark grey in color without foul odor and attained an ambient temperature after 30 days of composting, indicating the stable nature of composts. Additional researches are required in order to optimize the better organic and nitrogen compounds degradation during co-composting process.