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    The occurrence of chromatiaceae in waste treatment lagoons and their utilisation to treat fellmongery effluent : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University
    (Massey University, 1979) McFarlane, Paul Northcote
    A study of the occurrence of Chromatiaceae in waste treatment lagoons was made. To determine the important factors leading to their dominance, an investigation of the effect of various environmental parameters on the growth of a Chromatium species was made. Chromatium minutissimum was isolated and identified from an anaerobic lagoon treating meatworks effluent. An experimental design was used to screen the effects of temperature, pH, sulphide and acetate concentrations and light intensity on the batch growth of this bacterium in pure culture. Empirical models were developed which described the maximum population and the exponential growth rate as a function of these variables. Comparison of these models with lagoon data indicated that they provided a conservative estimate of the exponential growth rate and maximum population under lagoon conditions and that, under the range of environmental conditions expected in New Zealand, the hydraulic retention time is of major importance in limiting the development of this phototrophic bacterium in lagoons. The developed models may possibly be used to characterise the growth of other Chromatiaceae. To study the growth of the Chromatiaceae in mixed culture various lagoon samples were incubated in daylight. A succession from anaerobic non-phototrophic bacteria to phototrophic bacteria to algae was observed in these batch cultures. Thus, in addition to low hydraulic retention times preventing the growth of the Chromatiaceae, competition from the algae precludes their dominance at longer retention times. Seven lagoon systems in which the Chromatiaceae were known to occur were then investigated. The lagoons studied ranged from facultative to anaerobic. The wastes treated varied from domestic sewage to strong industrial and agricultural effluents. A succession from non-phototrophic anaerobes to Chromatiaceae to algae was observed in many instances and a three stage succession theory was formulated. This theory was used to explain the occurrence of the Chromatiaceae in all the lagoon systems studied and it may be used to design lagoons in which the dominance of the Chromatiaceae is favoured or prevented. The study of the lagoon systems indicated the potential of the Chromatiaceae for treating effluents containing reduced sulphur compounds. In N.Z., fellmongery effluent is the most important sulphide-bearing effluent. Experiments were therefore performed to develop criteria for the design of anaerobic lagoons using the Chromatiaceae to treat fellmongery effluent. Experiments were conducted to determine the effects of temperature and sulphide concentration on the performance of .088 m3 laboratory lagoons, in which Thiocapsa roseopersicina was dominant, treating a synthetic fellmongery effluent. Temperatures from 10°C to 25°C and influent sulphide concentrations of 200 mg/l to 1,500 mg/l were studied. Good treatment was obtained under a wide range of conditions although inhibition of growth occurred at influent sulphide concentrations of approximately 900 mg/l. Concentrated fellmongery effluents may therefore be treated by these lagoons. COD removals varied from 66.1% - 87.1% and sulphide removals from 89.5% - 98.4%. Design equations which described the performance of the laboratory lagoons were developed. To confirm the accuracy of these equations, pilot scale experiments were conducted on a 5.74 m3 lagoon system treating actual fellmongery effluent. A good degree of treatment was again achieved and the laboratory-developed equations provided a good estimate of the pilot-scale effluent over the range of conditions studied. Suitable criteria have therefore been developed for the design of anaerobic lagoons using the Chromatiaceae to treat fellmongery effluent.
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    Anaerobic filtration of waste waters arising from the production of bakers' yeast : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University
    (Massey University, 1984) Barnett, John William
    A study was carried out to assess the effectiveness of the anaerobic filtration process in providing a relatively simple on-site waste pretreatment system for the wastes from the production of bakers' yeast. These are of a high strength and acidic nature. To maintain practical constraints on the project a real waste water was used. The waste water is low in suspended material, has a high organic matter concentration giving a COD of 70000 to 90000 mg/l (BOD5 14250 mg/l and a pH of 4.5 to 5.0. Two experimental anaerobic filter units were constructed of glass cylinders packed with glass 'Raschig' rings as the inert support matrix, and used in the trials. A statistically designed experimental programme was used to test the effects of inflent substrate concentration, hydraulic retention time, temperature and filter unit on the filter response variables. Substrate concentrations of 5500 to 47200 mg COD/l (1000 to 9000mg BOD5/l) and hydraulic retention times of 1 to 5 days were used which gave rise to organic loading rates of 1.15 to 47.2 kg COD/m3d (0.2 to 9.0 kg BOD5/m3d). Empirical models were derived from the response data, using multiple regression techniques, and describe COD removal rate, total gas production, methane production and conversion of COD to methane in terms of the independent process variables. Results showed that the anaerobic filter achieved COD removals of 34 to 65 percent with corresponding conversions of 24 to 78 percent efficiency to methane at loadings of up to 47.2 kg COD/m3d. The empirical equations were able to explain 92 to 97 percent of the observed variance. The system was stable over the entire range of applied conditions.
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    Factors influencing the rate and stability of the anaerobic digestive process : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University
    (Massey University, 1986) Mawson, Andrew John
    Three factors affecting the rate and stability of the methane fermentation of a readily-hydrolysable feedstock were investigated. The aim of this work was to develop improved processes and control strategies to facilitate economic treatment of industrial wastes by anaerobic digestion. A comparison was made between the performance of a continuously-fed digester and semi-continuous digesters slug fed every second day. A semi-synthetic medium with glucose as the major carbon and energy source was used and seed material was transferred between the digesters, which were operated under similar loading conditions. The continuous digester repeatedly failed even when operated at dilution and loading rates much lower than the maximum values commonly reported. In contrast, the semi-continuous units provided satisfactory performance and could be easily and rapidly recovered from retarded operation. Failure of the continuous digesters was characterised by a steady fall in volatile suspended solids concentration followed by a rapid accumulation of acetate, and was attributed to a deficiency in the medium of one or more essential nutrients. These were thought to be provided in the semi-continuous digester by lysis of acidogenic bacteria or luxury uptake from the medium. Degradation of acetic and propionic acids was investigated in batch culture. Increasing the concentration of either acid from low levels decreased the rate of utilisation of the acid, but the proposed inhibitory role of un-ionised acids was not conclusively supported. Increasing the initial acetate concentration above 1000 to 1500 mg.l-1 significantly reduced the rate of degradation of propionate added at 500 mg.l-1. When acetate was added at 2000 mg.l-1 the rate of propionate utilisation was approximately half of that when acetate was present at 500 mg.l-1 or lower. In batch culture experiments, addition of up to 3.2 mM cysteine-hydrochloride or sodium sulphide, or 4.4. mM sodium thioglycollate did not inhibit total gas production from samples drawn from the continuous digester. However thy rate of methane production in effluent samples from a semi-continuous digester was inhibited by 25 % to 30 % by addition of 3.2 mM cysteine or sulphide. Inhibition was attributed to the sulphide ion. Sodium thioglycollate did not inhibit methane production from acetate but propionate degradation was markedly reduced, with increasing inhibition noted with increasing incubation time. The work adds to a considerable body of investigation into the factors influencing anaerobic digestion and the unresolved problem of process stability in long-term operation of conventional stirred tank digesters has again been highlighted. Indicators and possible causes of process failure have been suggested and further development of these should assist in the continuing increase in the rate of treatment while ensuring acceptable working margins of safety for the process.
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    Aerobic thermophilic composting of piggery solid wastes : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Environmental Engineering at Massey University
    (Massey University, 2001) Pandey, Surya Prakash
    Commercial piggery operations produce substantial quantities of solid waste requiring further treatment and disposal. Screened piggery solids contain recyclable nutrients and pathogenic organisms. Point source contribution from piggeries to surface and ground water pollution can be minimised by the application of composting process and technology. This process can serve as the treatment component of an overall waste management plan of a commercial piggery to biologically convert the putrescible to a stabilised form free of pathogenic organisms. The rate of biochemical reaction determines the speed at which composting can proceed. Solids Retention Time (SRT) is the most important factor in determining the stability of the compost product. SRT is function of, among many other factors, the type of substrate and amendments and their corresponding reaction rate constants. In order to establish the minimum SRT, it is important to correctly derive the reaction rate constant from decomposition data. Rates of decomposition vary widely depending on the organic substrate. Although numerous guidelines are available for the design of effective composting plant, most of these guidelines or studies deal with sewage sludge or municipal solid waste. There is a complete lack of data on composting process design or reaction rates for piggery solids. Due to these specific concerns, the main objectives of this thesis were to examine the composting process in relation to bulking material and operating conditions; analyse the disappearance of Total Organic Carbon with temperature development in order to determine first order reaction rates; and to analyse the inactivation or decay of indicator pathogens in piggery solids and sawdust composting trials and experiments. Aerobic static pile composting of piggery solids was investigated at pilot (5 m3) scale. Sawdust was used as the bulking agent to provide additional carbon and to increase the porosity of the substrate. Composting trials, using different substrate to bulking agent ratios and aeration frequencies were performed. The composting mixture was placed over an aerated base in the form of a pile. Temperature development, pH, Total Nitrogen. Total Phosphorus, Total Organic Carbon, Total Solids, Volatile Solids and pathogenic indicators were monitored until the completion of the trial. The development of temperature profiles in three layers of the pile in each trial was similar and in agreement with trials conducted by various researchers. The change in moisture levels at two sampling points within the compost heap for each trial were similar. The moisture removal results demonstrated that the moisture removal from the compost pile depends not only upon a suitable temperature range, but also on the mode of heat movement. The increase in Total Solids and decrease in the fraction of Volatile Solids during the composting period in many trials were in agreement with trends described by many authors and demonstrated the decomposition process. The nutrient analysis showed that up to 75% of initial nitrogen was conserved in the compost while there was no significant change in phosphorus concentration. There was varying order of magnitude reduction in Streptococci numbers in different trials. Similar trends were observed for total coliform(MPN) reduction. The high temperatures of the pile for prolonged periods were expected to decrease the bacterial counts to levels lower than those observed. The high values of MPN indicate that there are certain spore formers which survive the composting process. The decomposition curve of Total Organic Carbon was used to calculate rate constant (k) over time from the temperature development data. A medium-order. Newton-Raphson algorithm, which solved non-stiff differential equation was used to solve the reaction rate equation numerically. Two models were compared for the determination of reaction rate constant. Values of reaction rate constant varied under different operating conditions of compost piles. The best values of reaction rate constant of the order of 0.008 and 0.007 per day were obtained from trial 4 that used a 25:75 (volume basis) sawdust-waste ratio; and was aerated for 10 minuted every hour. Same trial had the lowest Mean Residence Time (MRT) of approximately 115days. Two controlled laboratory experiments at 70 °C and 60 °C, respectively were also performed to independently verify rate constants developed from pilot trials. Laboratory experiments gave similar reaction rate constants to those mentioned above. This is beside the fact that a constant temperature profile was maintained throughout the composting period in these two experiments. The average residence time of solids under controlled conditions was not very different from MRT values obtained in the same pilot trial. A comparison of two models showed that a simple first-order kinetic model can be used for the determination of inactivation coefficient, but using Arrhenius equation incorporating the reference temperature would provide a better thermal inactivation coefficient estimates. In trial 4, inactivation rate coefficient values were of the order of 0.394 and 0.380 per day at two sampling positions, respectively. The laboratory experiments provided inactivation rate coefficient values of the order of 61.97 and 47.34 per day, respectively. The significant difference in the reduction of indicator microorganisms between pilot trials and controlled experiments emphasises that homogeneity is critical in any composting process. It also emphasises the need for a temperature feedback aeration system.