Biological Wastes最新文献

A pilot plant was constructed to investigate the use of integrated ponding systems for municipal wastewater treatment in arid regions. The main objectives of this study were to determine the wastewater treatment efficiency of this system and to investigate the algal productivity under various operational and environmental conditions.

Treatment efficiency was determined in the facultative and high-rate ponds which were operated in series at various water depths, organic loadings and detention times. Control ponds with fixed parameters were also operated. The results showed the efficiency of this system in removing organic content of the municipal wastewater. Removals of up to 95% BOD, 85% COD, 90% ammonia and >99% of the pathogenic indicator microorganisms were achieved. Equations relating to algae productivity. Secchi disk measurements, suspended solids measurements and algae counts were developed. Algae productivities of 150–300 kg ha⁻¹ day⁻¹ were obtained under favorable conditions. Generally, high productivities were obtained at low detention times and greater pond depths in high-rate ponds, and at high organic loading within the ranges investigated.

The paper reports on the crude nutrient content and the mineral profile, as well as the apparent digestibility by ruminants, of faeces of poultry, pigs and cattle, poultry litter and solid matter of poultry, pig and cattle slurries. The second part of the paper deals with chemical treatment of pig and cattle slurry solids with NaOH, KOH and urea.

Nutrient and mineral content as well as digestibility of animal excreta are greatly influenced by species, age and type of feeding, the bedding material used and the method of solid-liquid separation of slurries.

The digestibility of poultry excreta is higher than that of pig waste. Cattle faeces are unsuitable as feeds even after chemical treatment.

In sacco degradability, apparent digestibility, energy content and intake of pig slurry solids were increased by treatment with urea, NaOH and KOH. Level of chemicals used and temperature influenced the effect of treatment. Wet pig-slurry solids may be preserved with urea.

Anaerobic digestion of olive oil mill wastewater was investigated using an upflow anaerobic sludge blanket (UASB) pilot plant and a laboratory fixed-bed upflow digester. Fatty acids contained in olive oil mill wastewater undergoing anaerobic treatment were degraded in both plants via hydrogenation of the double bond followed by depolymerisation. A similar behaviour was found to occur in wastewater stored in tanks for several months.

With the objective of obtaining the most complete recovery of carbohydrate content from agricultural wastes, a process has been studied which involves three stages: (1) water-soluble sugar extraction; (2) pentose preparation by mild hydrolysis; and (3) hydrolysis under more drastic conditions of residual lignocellulose.

In this paper we report on the mild hydrolysis of pentosans from corn cobs in pre-pilot columns. This was done using a process which involved impregnation with sulfuric acid, heating to hydrolyse the wet acidic waste, and watery pentose extraction. The influence of acid concentration and heating time at 100°C on the hydrolysis as well as on sugar degradation and yields has been studied.

The optimum conditions of the process were 9% sulfuric acid and 3 hours heating. Under these conditions, 89% of the total pentosans (t.p.) were hydrolyzed (28% of the raw dry material, r.d.m.); 33% t.p. (9% r.d.m.) were degraded, and 67% t.p. (20% r.d.m.) were recovered in the broths. The broths obtained were purified with ion-exchange resins and good yields of xylose were obtained by crystallization.

Conditions for the direct reduction of the deionized xylose broths to xylitol, as well as yields and the technical properties of the products, were also studied.

Tannins were determined by various chemical and biological methods in 15 agro-industrial by-products. Tannins in terms of total phenols (TP), condensed tannins (CT) and protein-precipitation capacity (PPC) were very high in Acacia nilotica and Theobroma cacao pods, Mangifera indica seed kernel, Panicum miliaceum polish and cakes of Madhuca indica seed and Garcinia indica. The correlation coefficients of PPC (measure of biological activity) with TP (0·81), degree of polymerisation (−0·83) and protein-precipitable phenolics (0·96) were significant (P < 0·05), but that with CT (0·34) was not significant. It is inferred that TP rather than CT contribute significantly towards PPC and that highly-polymerised tannins do not bind proteins as efficiently as the lesser-polymerised ones.

The TP and CT were low in pods of Prosopis juliflora and Pithecolobium saman, Cassia tora seeds, cakes of Guizotia abyssinica, Pongamia glabra, Schleichera oleosa, Hevea brasiliensis and Hibiscus cannabinus and Panicum miliaceum bran. The PPC could not be detected in these by-products, suggesting that these nine by-products can be considered safe for incorporation in livestock feed, subject to absence of other deleterious factors.

The trans-isomer of sodium ethylenediamine-tetraacetic acid (EDTA) was used to chelate metal ions known to inhibit accurate determination of BOD of wastewater. The results showed that as much as 5 mg Cu(II) and 6 mg Zn present in a litre of poultry wastewater were effectively chelated by 1 ml of 0·1 m EDTA so that the metals had no suppressive effect on the BOD values.

A set of 10 upflow sludge blanket digesters was examined as five pairs—one control and four test reactors—to assess the way in which selected types of carbonaceous substrate affected the performance of the reactors. The carbon sources were sucrose, acetate, casein, butanol and ice cream. The results show that the change of feed caused a deterioration in the performance of all the test digesters. The casein feed caused the greatest impact, with de-amination of the protein producing inhibitory levels of ammoniacal-nitrogen. The use of ice cream in the feed resulted in the surface of the sludge granules being covered with what was thought to be lipid material.

In a first small silo study four mixtures of swine waste, wheat straw and cane molasses in various proportions were ensiled. The mixtures were adjusted to a moisture content of about 40% before a 42 days ensiling period at 28±2°C. Ensiled mixtures had an acceptable aroma and appearance similar to that of good quality haylage. In a second small silo study, three replicates of a factorial experiment were run in the laboratory for three levels of swine waste: 11, 22 and 44% (dry basis) and three levels of moisture content: 40·8±0·5, 54·4±0·7 and 69·0±0·6. After a 42 days ensiling period at 28±2°C, the silos were opened and evaluated. All mixtures preserved well and appeared to show typical haylage fermentation characteristics. Lactic acid concentration and pH indicated that good ensiling occurred in all mixtures. All mixtures were free of total and fecal coliforms, Salmonella, Shigella and Proteus organisms. As the proportions of swine waste in the mixtures decreased, percentages of crude protein and ether extract decreased linearly and quadratically (P<0·0.01). Crude fiber increased linearly as the proportion of swine waste decreased in the mixtures (P<0·01). Ash increased linearly as the proportion of manure increased in the mixtures (P<0·01).