Biological Wastes最新文献

The charred waste obtained on treatment of the bark of a tree (Terminalia tomentosa, Cambreatacea) with sulphuric acid for the manufacture of oxalic acid has been identified as a good adsorbent for toxic ions (Pb²⁺, Hg²⁺, F⁻ and Cr₂O₇²⁻) and dyes.

The anaerobic digestion of papermill sludge containing a high amount of inorganic matter was studied. Despite the presence of about 58% inorganic matter in the substrate, a high rate of hydrolysis and subsequent acid formation could be achieved in an acidogenic reactor which was inoculated with rumen microorganisms. Degradation efficiency of neutral detergent fibre amounted to 62% at high loading rate (34·2 g volatile solids per litre per day) and short solid retention time (51 h). In order to study the effect of accumulation of inorganic matter in the reactor, degradation efficiency was studied at various loading rates and solid retention times. An increase of solid retention time to 74 h resulted in a decreased degradation efficiency, probably due to an increased ash content in the reactor under these conditions. The effect of inorganic matter accumulation was also studied after coupling of the rumen derived acidogenic reactor to an upflow anaerobic sludge blanket-type methanogenic reactor. By using this two-stage digestion process an overall conversion of papermill sludge into biogas could be realized. The operation over about three months of the two-stage process was studied in terms of process stability, nutrient recycling and accumulation of inorganic matter.

In this paper, the kinetics and economics of substrate degradation and biogas production are discussed. Mass balance on substrate, with either the Contois or Adams-Eckenfelder models, is used to design the mathematical models of volatile solids reduction and biogas fermentation. The predictions of both the models are found to be in close agreement with the observed values reported. A computer model based on a system dynamics approach is used to model the economics of biogas production by anaerobic digestion from cattle slurry available from typical rural families in Bangladesh. This model incorporates the Adams-Eckenfelder model to determine the amount of gas production and the technique described by Audsley and Wheeler (J. Agric. Engng Res., 23, 189–201) to take into account the effects of price, interest, and inflation. The effects of changes of these parameters on the net profit or loss from the process are also considered.

A laboratory-scale sequencing batch reactor was fed with synthetic wastewater based on sucrose to determine the biokinetics of the process. The values of u_max and K_s were found to be 0·32 h⁻¹ and 563 mg/litre, respectively, while the yield constant was determined to be 0·656 with a standard deviation of 0·102. COD removal was good. The relationship between the food:microorganisms (F/M) ratio and SVI was explored and results showed that increases in the F/M ratio led to decreases in SVI values. The initial adsorption of substrate was proportional to the amount of biomass in the reactor. Comparisons between changes in MLVSS and Total Viable Count were made and MLVSS was not found to be a good indicator for the viability of organisms in the reactor.

An overview of the availability of bagasse and cotton plant stalk in India for manufacture of pulp and paper is given. The properties of pulp and paper produced using both the raw materials separately and in blends have been discussed. The possibilities of using kraft pulp of cotton-plant stalk for blending with chemi-mechanical bagasse pulp, replacing hardwood pulp, have been explored. Addition of kraft pulp of cotton-plant stalk in various proportions yielded papers with improved properties.

Sugarcane trash, paddy straw and wheat straw are the main farm by-products and are mostly underutilized. A large portion of these farm products goes to waste. These by-products could be successfully utilized as thermal insulators, if used in a high-density, compressed wafer-form.

Vermicomposting has the potential to convert many organic wastes into useful plant growth media. However, the rotary screens previously employed to separate worms from vermicompost often became blinded, making worm separation slow and inefficient. An improved method was required. An experimental machine employing a novel combing action to achieve separation was therefore constructed and tested. The comb-type mechanical separator was shown to be effective with vermicomposts which were well-worked and had moisture contents of 80% wet basis or less. For example, using well-worked vermicompost derived from separated cattle solids and containing approximately 5 kg of worms/m³ and with a moisture content (wet basis) of 75%, a throughput of 1·5 m³/h of vermicompost was possible, with a separation efficiency of 95%. Vermicomposting beds are sometimes maintained at moisture contents higher than 80% wet basis, and the degree of worm-working achieved can vary. Further work is therefore required to assess the performance of the comb-type separator over a wider range of conditions.

Two downflow anaerobic filters with different plastic media of the same specific surface area, treating currant-finishing wastewater are described. COD removal for modular plastic media with a cross-flow design was 80% and 75% for loadings of 8 and 10 kg COD/m³ day respectively. COD removal for pall-rings media gradually decreased from 90% to 57% as loadings gradually increased from 0·6 to 6 kg/m³ day. The downflow anaerobic filters have a low performance compared with other high-rate anaerobic reactors, the UAF, UASB and AFB.

Laboratory trials were carried out to determine the suitability of guar and sorghum stalks from Sudan as basic materials for composite insulation boards manufacture using cement as binder. Lignocellulosic material-to-cement ratios of 1:15 and 1:2 were used. The results show that these raw materials could successfully be used for insulation boards, with density of 530–700 kg/m³, satisfactory strength, and very good heat-insulation properties making them suitable for building.

The oil-synthesizing capacity of Candida curvata D was evaluated with different pH, temperature and carbon sources. The microbial oil contained a wide range of fatty acids, ranging from C₁₂ to C₂₂. The proportion of lipid fractions, as well as fatty-acid composition of the cells, varied with temperature, pH and medium. Under all conditions the studied oils were rich in octadecenoic, stearic and linoleic acids.