Biological Wastes最新文献

Candida utilis and Saccharomyces cerevisiae were grown on raintree-pod extract as a sole carbon and energy source. It was found that the pod extract could serve as a suitable medium for the cultivation of Candida utilis for the production of single cell protein.

Some physical parameters were determined on an organic product derived from a new phytodewatering process of anaerobic sludge, in order to verify its possible use as a substrate. Wetting-drying cycles were carried out with a sandy soil, and with mixtures of this soil with the organic product taken before and after the phytodewatering process. The phytodewatering process decreased bulk density while raising aggregate stability and friability.

Production of biogas from mixtures of fresh and partially-decomposed Ageratum with cattle dung were studied in batch digesters at 30 ± 1°C. Partially decomposed Ageratum produced 319·4 litres of gas per kg dry matter as compared to 222·4 litres of gas per kg dry matter from pure cattle dung. Fresh Ageratum supplemented with cattle dung in a ration of 3:2 (wet weight basis) did not produce any gas, because of the accumulation of excess acids. In contrast, similar mixtures of partially decomposed Ageratum and cattle dung yielded about 9% more biogas than did pure cattle dung. The methane contents of the gas obtained from Ageratum mixtures were 62–77% as compared to 56–60% from pure cattle dung.

Solid-state fermentation of wheat bran by Aspergillus niger for glucoamylase production was studied. Whole dough containing spores, and wheat bran, was used as inoculum and a 5% (w/w) level was found optimum for enzyme production. Improved nutrients supplementation, addition of whole corn (yellow) flour and better process controls resulted in a 5–6-fold increase in enzyme yield over preliminary results from laboratory-flask experiments. The productivity was about 520–560 IU enzyme per gram dry substrate in 96 h. When scaled-up in tray fermenters, about 80% enzyme production was achieved in comparison to flask experiments, in 36 h.

A comparative analysis of the performance of digesters in the treatment of the organic fraction of municipal solid waste, sorted at source or mechanically, is carried out. The comparison is performed in terms of the percentage of biodegradation achieved, the kinetics of the process and the biodegradability of the substrate. To help the comparison some mathematical relationships are deduced. Data from our own studies are considered in conjunction with data from the literature, most of which refers to pilot plants.

The effect of temperature on the composting of bark in adiabatic and fixed-temperature reactors was studied with respect to decomposition, loss of phytotoxicity and a reduction in the production of Aspergillus fumigatus spores. High temperatures could be maintained for long periods using an adiabatic reactor and the temperature could be controlled by aeration. In fixed-temperature reactors, the optimal temperature for decomposition was either 40 or 50°C. Phytotoxicity, as determined by an in-vitro seedling assay, was reduced more quickly by 50°C composting than by 40°C. In addition the growth and sporulation of a potential human pathogen, Aspergillus fumigatus, was less at 50°C than at 40°C.

A simple mathematical model of steady-state attached-growth anaerobic fermenter kinetics is described. The model considers a single methanogenic culture following Monod growth kinetics. The model accounts for effects of influent biodegradability and volatile solids concentration, temperature and hydraulic retention time, and predicts volumetric methane productivity and volatile solids reduction. It is distinguished from conventional suspended-growth reactor models by its explicit consideration of bacterial concentration in the reactor system, based on hydraulic flow and influent volatile solids concentration. The model was validated using data from both porous- and solid-media attached-growth fermenters.

Studies are made of the anaerobic digestion of olive mill wastewater (OMW) using bioreactors housing various suspended supports for immobilization of the microorganisms. The OMW inhibited the digestion as the digester loadings increased, and the support medium affected the inhibition. By applying the international Time Series Processor (TSP) computer program, version 4·0 D (Stanford, CA, USA), through the Roediger equation G = G_mm[1 − exp ( − K_obst)], to the resultsobtained the G_m and K_obs values were calculated. From the G_m values was then calculated the coefficient of yield for each support. The results show the influence of the different supports used to immobilize the bacteria on the biomethanation of OMW; this is of relevance to the development of fluidized-bed processes.

This experiment explored the possibility of treating pig manure plus sewage sludge by anaerobic digestion, using batch fermentation at 37°C.

The results indicated that the digested materials contained a lower level of putrescible matter when compared to the raw materials. Co-digestion of pig manure and sewage sludge at the ratio of 2:1 seemed to give the best results in terms of reducing the organic load and yielding a higher volume of methane.

The experiment should be repeated in digestion tanks of a sewage treatment plant, especially for treating pig manure which has been recognized as the major source of water pollution in Hong Kong.