Bioflocculation is a well known phenomenon in wastewater treatment and aids in the clarification of polluted waters. The work described in this paper was designed to study the effect of bacterial communities on floc sizes and numbers by applying a series of bench scale experiments. Pure, mixed isolates and the natural population of bacteria were grown separately in the effluents of some agricultural activities, effluents from foodstuff industries and municipal sewage. Numbers and sizes of the developed flocs were determined after shaking at a constant temperature.
Rapid pyrolysis of rice hull was studied in a Curie-Point pyrolyzer with heating rates between 1500 and 2000°C s−1, depending upon the Pyrofoil used. Primary pyrolysis occurred vigorously between 400 and 600°C to yield tar, light organics, H2O, CO2 and CO. As temperature went over 600°C a small amount of heavier primary products was further cracked into CO and light hydrocarbons. The amount of char residue decreased with temperature and finally reached an asymptote of 24%; this value was about 10% lower than that obtained in a slow heating thermogravimetric analyzer (TGA). Below 800°C the effect of residence time on rice hull devolatilization was significant whereas, at higher temperatures, the pyrolysis was so rapid that it virtually completed during the heating up period. Pyrolysis of cellulose and lignin yielded liquid tar and solid char, respectively, as the major products; the yield of char and total volatiles from the pyrolysis of rice hull could be estimated from their yields in the pyrolysis of cellulose and lignin.
Organic soil amendments in the form of chopped shoots of some weeds gave significant reductions in the population build-up of the root-knot nematode Meloidogyne incognita and the stunt nematode Tylenchorhynchus brassicae on a strong host, eggplant cv. ‘Pusa Purple Long’. The most effective was soil treated with Solanum xanthocaroum followed by Calotropis procera, Datura metel, Croton bonplandianum and Argemone mexicana. These treatments also inhibited significantly root galling. The plant growth of eggplant was also improved by the amendments; however C. bonplandianum showed some phytotoxicity at higher dosage.
A comparative study of a bench-scale and a pile composting showed that the C/N, ash percentage and alakaline phosphatase activity were potentially useful parameters for estimating the maturation of cattle manure compost. The values of these parameters were nearly constant during a simulated poor composting, whereas they changed significantly during an optimal process. Other parameters—decomposition degree, chemical oxygen demand, invertase and Rusch number—were less sensitive indicators of composting. The use of these data for agricultural compost samples has shown that high alkaline phosphatase activity and No3−/NH4+ ratio were correlated with compost maturity.
Protein enrichment of rice straw was attempted by subjecting it to fermentation with a strain of Cellulomonas (CBS.7) which was originally isolated from decomposing cotton debris. Maximum cellulose utilisation (73·2%) was recorded with ammonium sulphate as nitrogen source, supplemented with biotin, at pH 7·5 within 72h of fermentation. Pretreatment of milled rice straw with a 2:1 mixture of NaOH (5%) and H2O2 (1%) resulted in lignin reduction from 13·32 to 3·52%. Treated straw yielded 189–195 mg of protein per 100 ml of medium in a period of 120 h of fermentation under shaker-grown condition. Growth in a bench-top fermenter resulted in a protein yield of 1183 mg of protein per litre of medium excluding straw-bound particulate protein. The nutrient profile of bacterial SCP produced is also reported.
The action of cellulose preparations from Aspergillus niger and Rhizopus sp. strains (4000 U g−1) were tested on cellulose powder, newspaper pulp, rice straw dust, wheat straw dust, cotton stalk dust and sawdust. Both enzymes resulted in saccharification yields around 40% on cellulose powder and around 30% on newspaper pulp, whereas the yields were below 3% for all other materials tested. Different pretreatments of some of the more resistant cellulosic raw materials prior to enzymatic action resulted in slight increases in saccharification yields. The most effective was treatment with 0·5n acid or alkali which resulted in an increase in saccharification yields of the order of three- and four-fold respectively.
Runoffs from six rural watersheds in the Coastal Plain were monitored over a period of five years. Nitrogen, phosphorus and COD loading rates were developed for all the watersheds and related to land use and soil type. The nitrogen, phosphorus and COD content of rainfall was also measured.
Aerobic pretreatment of palm oil mill effluent (POME) greatly reduces the C, NO3N and NH4N content of POME but increases the organic N and pH. Results obtained indicated that pretreatment of POME before land application would reduce the risk of waterway pollution from runoff. The aerobic pretreatment would also make more organic N available to plants. Application of pretreated POME, which was alkaline in nature, to acidic soil would be an added advantage. The changes in the composition of the POME occurred faster at 37°C than at 25°C or 4°C.
The effects of the incorporation of silkworm larval litter and poultry droppings with cowdung in relation to biogas generation and microbial properties at 37°C and 28±2°C are discussed. The maximum gas (506 millilitres per gram of Volatile Solids destroyed) was recorded in the poultry droppings with cowdung slurry (T2), which gave the maximum count of 217·5 × 103 methane bacteria per gram. The carbon dioxide content was minimum (32%) in the biogas. The manurial values of the digested slurries of various wastes are also discussed. The trend of the data suggests the possible utilization of silkworm larval litter and poultry droppings as supplementary feedstocks for biogasification.
This paper reports the change in the bulk density of the residues of ten different crops, commonly cultivated in north India, as a result of the application of uniaxial pressure. Empirical relationships between the magnitude of pressure and the resultant density are developed for each residue. The results are compiled and presented in the form of a nomogram from which the density of any residue corresponding to a particular uniaxial pressure can be easily determined. The information presented in this paper will be useful in designing the process and equipment for the densification of crop residues.
Wheat straw cellulose was used as substrate for single cell protein (SCP) production using C. globosum, a non-toxic fungus. Both untreated and delignified powdered (60 mesh) substrate were used in submerged fermentation. The optimum cultural conditions for maximum conversion of wheat straw into SCP were 5 days, 37°C, pH 5·0 and 400 mg litre−1 nitrogen in the form of sodium nitrate.
A two-step method is described in which cattle manure is added to seawater and the resulting elutriate is used for the mass culture of two species of algae—Tetraselmis sp. and Chaetoceros gracilis—and the algae are then fed to the brine shrimp, Artemia salina. An initial biomass of 190 g of brine shrimp increased to 2500 g in 14 days. The system is simple to construct and manage, and may serve as a model for other systems used to support aquaculture facilities or may stand by itself if devoted to the tropical fish hobbyist market.
Laboratory scale, downflow stationary fixed-film reactors with polyester cloth support and a surface-to-volume ratio of 86 m2 m−3, operated continuously at 35°C, were capable of treating red beet wastewater with an organic strength between 5000 and 15 000 mg COD liter−1, at up to 87% COD removal efficiency. Organic loadings of up to 24 kg COD m−3 day−1 were achieved with COD removal rates of up to 16 kg COD m−3 day−1 and methane production rates exceeding 4 m3 m−3 (reactor volume) day−1. Loadings of 30 kg COD m−3 day−1 and HRT of 5 h were achieved without process failure. The actual amount of waste organics converted and methane gas produced increased with increased loading, even though COD removal efficiencies decreased. A wide range of waste organic strengths could readily be treated but maximum methane production and COD conversion rates would be achieved with increased waste organic strength. Biomass yield increased with increased organic loading and was slightly influenced by waste organic strength.
Our previous experiments showed that flowering Chinese cabbage (Brassica parachinensis) and Chinese radish (Rhaphanus sativus) var. longipinnatus grown in soil amended with sewage sludge and animal manure accumulated Pb, Cu, Zn and Mn. In this experiment, caterpillars of the common white butterfly (Pieris canidia) were fed with the waste-grown vegetables. Caterpillars fed with sewage sludge-grown vegetables had a lower body weight and a higher level of heavy metals than those fed with animal manure-grown vegetables (average fresh body weights of caterpillars fed with waste-grown leaves of Chinese radish were 75, 122, 186 and 196 mg for activated sludge, digested sludge, chicken manure and pig manure, respectively). Those fed with flowering Chinese cabbage accumulated a higher level of heavy metals than those fed with Chinese radish (Pb, 6·7-fold, Cu, 6·0-fold, Zn, 6·8-fold and Mn, 5·7-fold in treatments with activated sludge). As a whole, the accumulation of heavy metals in the caterpillars, in descending order, was from vegetables manured with activated sludge, digested sludge, chicken manure and pig manure.
Adhesive resins based on modified onion skin tannin extract have been prepared for gluing Sapele veneer panels. Results show that, on addition of paraformaldehyde, the resins cure at ambient conditions to a strength and durability satisfying the requirements of the International Standards Organization.
Etude experimentale de l'effet d'une elevation progressive de la temperature de 55 a 60°C sur les performances d'un digesteur de fumier de porcin
Chemical and physical composition, particle size distribution and settling behaviour of faeces from eleven intensive commercial piggeries and one research piggery were investigated.
Effluents from anaerobic lagoons were treated in two parallel aerated lagoons, at variable organic load and hydraulic residence time. The removal of total Kjeldahl nitrogen (TKN) was found to increase rapidly at higher TKN food to microorganisms (F/M) ratios. At BOD F/M ratios below 0·6 kg kg−1 day−1 nitrification manifested itself through accumulation of oxidised forms of nitrogen. The apparent decrease in denitrification, evidenced by nitrites and nitrates present at these loads, can be attributed to an inadequate supply of easily available carbon as electron donor. Accumulation of nitrites at lower loads (higher residence times) might have been due to free nitrous acid toxicity to the Nitrobacter species. A maximum TKN removal of 50% was achieved at TKN F/M = 0·5, which corresponded to a BOD/TKN ratio of 3·4.
The specific heat of rice bran was determined by the classical method of mixtures. The specific heat of rice bran had a linear positive correlation with moisture content and temperature. The specific heat values increased from 0·4048 to 0·4976 cal/g°C when the moisture content was increased from 6·388% to 18·036% (wet basis) for the lowest mean temperature of 38·2°C, while the values increased from 0·4140 to 0·5290 cal/g°C when the moisture content increased from 4·265% to 18·036% (wet basis) for the highest mean temperature of 63·1°C.
