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    Wastewater effects on epilithon, particularly sewage fungus, and water quality in the Manawatu River, New Zealand : a thesis presented in partial fulfilment of the requirements of the degree Doctor of Philosophy in Biotechnology at Massey University
    (Massey University, 1985) Quinn, John Martin
    Epilithon development, in relation to the discharge of domestic sewage, dairy factory and meatworks wastewaters, and its effects on water quality were studied in laboratory channels and in the Manawatu River. During the three year period of the study the organic material inputs to this river were progressively reduced to meet the requirements of water rights designed to limit the in-river BOD5 to 5 g.m-3 at the end of a defined mixing zone with the objective of maintaining adequate oxygen levels and controlling sewage fungus growth. Laboratory channel studies demonstrated that, for a given BOD5 addition, untreated dairy factory wastewater increased the heterotrophic growth 2-3 times more than primary treated meatworks wastewater. Similar observations were made in the Manawatu River. These varied growth responses could be accounted for by the different relative contributions of dissolved and low molecular weight (< 1000 daltons) organic compounds in the different wastewaters. The dissolved or low molecular weight (determined after sample ultrafiltration) BOD5 therefore provide more reliable general sewage fungus control parameters than BOD5. Current velocity and spates had marked influences on the development of benthic communities. Maximum sewage fungus biomasses on the natural bed were observed at current velocities of 0.2 to 0.45 m.s-1. Short heterotrophic fronds occurred at the maximum current velocity investigated of 1.16 m.s-1. Small spates of up to 50 to 70 m.s-3 caused preferential sloughing of heterotrophs over epilithic phototrophs which had developed on concrete plates at river flows of approximately 25 m3.s-1. Flows in excess of approximately 150 m3.s-1 removed growths of Cladophora glomerata which had developed at sites where the pre-spate current velocity was 0.3 to 0.4 m.s-1. Much higher flows, in excess of 400 m3.s-1, were required to remove the dense growths of the macrophyte Potamogeton crispus. Observations of sewage fungus biomass at various depths in the Manawatu River and growth rates on both upper, sunlight exposed, and lower, shaded, surfaces of concrete plates suspended in the water column indicated that solar radiation inhibition of heterotrophic growth is not important in the Manawatu River. These heterotrophic growths in the river were replaced by heavy phototroph-dominated epilithon as organic concentrations were reduced. Both communities had significant impacts on the suspended biomass and dissolved oxygen levels in the river. A computer model simulating summer low flow conditions in the Manawatu River predicted that the river can sustain average respiration rates of 20 and 24 g 02 m-3 d-1 at mean river temperatures of 21°C to 12°C respectively without breaching the statutory minimum permissable dissolved oxygen concentration of 5 g.m-3. A multiple regression model of the factors influencing epilithon respiration was developed from in situ chamber studies of a range of epilithic community types. This gave adequate predictions when tested against measurements over reaches below the discharges and predicted that the benthic biomass resulting in the maximum permissible respiration rates decreased from approximately 143 g AFDW m-2 at 12°C to 34 g AFDW m-2 at 21°C. A management strategy limiting the organic, but not the nutrient, inputs to the Manawatu River was shown to be unlikely to ensure consistent maintenance of the statutory minimum dissolved oxygen concentration. The implications for management of the river are discussed,
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    Activated sludge treatment of dairy processing wastewaters : the role of selectors for the control of sludge bulking : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1996) Leonard, Anne M.
    The typical wastewater from a milk processing facility producing butter and milk powder was treated in a modified activated sludge system in order to establish process characteristics and investigate operational problems. A synthetic wastewater was developed with similar average physical and chemical characteristics to that from a full scale facility. The relative biodegradability of the wastewater fractions was assessed and basic microbial growth parameters also determined. A laboratory scale activated sludge reactor configuration was then established and its performance monitored. Although effective treatment was achieved in terms of suspended and soluble organic matter removal, the use of a completely mixed reactor resulted in the system becoming inoperable due to the excessive growth of filamentous microorganisms, with Type 0411 being the dominant filament. In order to inhibit filamentous bulking, various selector reactor configurations were trialed. As nitrification of feed stream proteins had been indicated, unaerated selectors were used with the intention of effecting anoxic substrate removal in the initial selector zone; but due to the limited supply of oxidised nitrogen, insufficient substrate removal occurred in the selectors to prevent filamentous bulking, with Type 021N becoming dominant. The next series of trials used aerated selectors, with some configurations demonstrating the ability to both prevent and cure filamentous bulking. The unsuccessful trials resulted in the proliferation of Haliscomenobacter hydrossis. From selector trials conducted it was established that the requirements for successful suppression of filamentous growth were the incorporation of an initial selector zone in which greater than 95% of removable soluble substrate was removed and the bulk solution was maintained in a fully aerobic state. Serial selector configurations demonstrated improved performance over a single selector. From observations of the physical conditions and substrate concentrations in the reactor configurations employed, a correlation of filament type to environmental condition can be tentatively made: Types 0411 and 021N were indicated to be low organic loading type filaments, whereas H. hydrossis was indicated to be a low dissolved oxygen filament. Rapid substrate removal rates were attributed to biosorption, accumulation and storage mechanisms, increasing as the selector configuration trials progressed. In general floc formers possessed a higher specific growth rate and substrate affinity than the filamentous microorganisms. Filament Type 021N was indicated to lack biosorptive capacity, however H. hydrossis was indicated as having a greater biosorptive capacity than the floc formers present. The highly degradable nature of the substrate and high substrate concentration gradients imposed by the selector configuration caused rapid oxygen uptake rates; resulting in aerobic, anoxic and anaerobic substrate removal mechanisms all occurring in the initial selector zone. The occurrence of simultaneous nitrification, denitrification and phosphorus accumulation resulted in significant nutrient removals from the aerated selector reactor system, with influent nitrogen and phosphorus levels each reduced by up to 96% in the effluent stream. This study found that an activated sludge process was an appropriate method for the effective treatment of milk processing wastewaters, as effluent suspended solids of less than 10 g.m-3 and soluble COD of less than 30 g.m-3 were consistently obtained, however a modified configuration would be required to prevent the growth of filamentous microorganisms and attendant operability problems. Due to the nature of dairy processing wastewaters, a selector reactor configuration could be employed not only to overcome potential filamentous bulking problems, but also to provide an opportunity for biological nutrient removal without the inclusion of dedicated anoxic / anaerobic reaction steps or the complex flow regimes conventionally employed for nutrient removal activated sludge systems.