Typescript. / Thesis (Ph. D.)--University of Hawaii, 1963. / Bibliography: leaves [127]-138. / xiv, 138 leaves ill., diagrs., tables (2 folded)

The objective of the research program was to demonstrate the technical feasibility of removing phosphorus, by the enhanced biological phosphorus removal mechanism, from domestic wastewater using a laboratory scale Sequencing Batch Rotating Biological Contactor (SBRBC). The rotating discs of the RBC were subjected to alternating anaerobic/aerobic conditions by varying the water level in the reaction vessel. At the start of the treatment cycle, the RBC reactor would be filled submerging the rotating discs and ensuring anaerobic conditions in the RBC biofilm. Acetate would be added to the reaction vessel at this time. Following the batch anaerobic react period part of the reactor contents were decanted to either the sewage feed tank or a separate holding vessel to later become part of the influent for the next treatment cycle. With the rotating: discs of the-RBC partially submerged oxygen was available to the bacteria, in the RBC biofilm. Three operating schedules were tried with the above process. Each operating schedule differed in the way the decanted wastewater from the anaerobic phase was handled. Batch tests were conducted weekly to determine the nature of the biological reactions taking place in each of the batch anaerobic and aerobic phases. The SBRBC process showed promise for enhanced biological phosphorus removal from domestic wastewater. Carbon removal and nitrification of the wastewater were secondary benefits to this process. The success of the process was found to be dependent on the attainment of proper anaerobic conditions at the start of each treatment cycle. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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The main objective of this project was to investigate and model phosphorus (P) transport in soil column studies. A model named HYDRUS-NICA was developed, by coupling a hydrological and transport model (HYDRUS-1D model) with an aqueous chemical model (non-ideal competitive adsorption - NICA), to improve the predictions of P transport in soil and water. The HYDRUS-NICA model was developed by replacing the non-linear empirical (Freundlich and Langmuir) equations of the HYDRUS-1D model with the NICA model equations. The numerical accuracy of the HYDRUS-NICA model was then evaluated by comparing the relative errors produced by the HYDRUS-NICA and HYDRUS-1D models. The results showed that the numerical schemes of the HYDRUS-NICA code are stable. / The ability of the NICA model to describe phosphate (PO4) adsorption to soil particles was tested using soils collected from agricultural fields in southern Quebec. The surface charge and PO4 adsorption capacity of these soils were measured. Results were used to estimate the NICA model parameters using a non-linear fitting function. The NICA model accurately described the surface charge of these soils and the PO4 adsorption processes. / The HYDRUS-1D model was applied to simulate water flow and PO4 transport in re-constructed soil column experiments. The HYDRUS-1D model was calibrated based on physical and chemical parameters that were estimated from different experiments. Overall, the HYDRUS-1D model successfully simulated the water flow in the columns; however, it overestimated the final adsorbed PO4 concentrations in the soil. The discrepancies in the results suggested that the HYDRUS-1D model could not account for the differences in the soil structure found in the columns, or that the Freundlich isotherm could not adequately describe PO4 adsorption. / The HYDRUS-NICA model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the HYDRUS-1D model. The overall goodness-of-fit for the HYDRUS-1D model simulations was classified as poor. The HYDRUS-NICA model improved significantly the prediction of PO4 transport, with the coefficient of modeling efficiency values being close to unity, and the coefficient of residual mass values being close to zero. The HYDRUS-NICA model can be used as a tool to improve the prediction of PO4 transport at the field scale.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1983. / Bibliography: leaves 213-230. / Microfiche. / xviii, 230 leaves, bound ill. 29 cm

Low availability of soil phosphorus (P) caused by strong sorption of P is a major constraint to agricultural production in most South African soils, particularly those from the high rainfall areas. The aim of this study was therefore to investigate whether combined addition of goat manure with inorganic P fertilizers could enhance P availability in some P fixing soils of the Transkei region, South Africa. The study addressed the following specific objectives (i) to assess P sorption capacities and requirements of selected soils and their relationship with selected soil properties and single point sorption test, (ii) to assess the effects of goat manure and lime addition on P sorption properties of selected P fixing soils (iii) to assess the temporal changes in concentration of inorganic and microbial biomass P fractions following application of inorganic fertilizer P with goat manure in a laboratory incubation experiment, and, (iv) to assess the effects of goat manure application with inorganic phosphate on inorganic and microbial biomass P fractions, P uptake and dry matter yield of maize. Sorption maxima (Smax) of seven soils examined ranged from 192.3 to 909.1 (mg P kg-1) and were highly and positively correlated with sorption affinity constant (r = 0.93, p = 0.01) and organic C (r = 0.71, p = 0.01). The amount of P required for maintaining a soil solution concentration of 0.2 mg P l-1 ranged from 2.1 to 123.5 mg P kg-1 soil. Soils collected from Qweqwe (a Cambisol), Qunu (an Acrisol), Ncihane (a Luvisol) and Bethania (a Ferralsol) had lower external P requirement values and were classified as lower sorbers, whereas soils from Ntlonyana (a Planosol), Chevy Chase (a Ferralsol) and Flagstaff (a Ferralsol) were classified as moderate sorbers. The results suggested that P availability could be compromised in 43 percent iii of the soils studied and that measures to mitigate the adverse effects of P sorption were needed to ensure that P is not a limiting factor to crop production, where such soils are found. Goat manure addition at varying rates (5, 10 and 20 tha-1 dry weight basis) to two of the moderately P fixing soils from Chevy Chase and Flagstaff, reduced P sorption maxima (Smax) compared to the control treatment. Phosphate sorption decreased with increasing amounts of goat manure in both soils but the extent of reduction was greater on Chevy Chase soil than on Flagstaff soil. The relative liming effects of the different rates of goat manure followed the order 20 t GM ha-1 > 10 t GM ha-1 > 5 t GM ha-1. In a separate experiment, addition of inorganic P at varying rates (0, 90, 180, and 360 kg P ha-1) to Flagstaff soil increased labile P fractions (resin P, biomass P and NaHCO3-Pi) and the increases were greater when goat manure was co-applied. The control treatments contained only 17.2 and 27.5 mg P kg-1 of resin extractable P in the un-amended and manure amended treatments, respectively which increased to 118.2 and 122.7 mg P kg-1 on day 28 of incubation. Biomass P concentration was increased from 16.8 to 43.9 mg P kg-1 in P alone treatments but the fraction was greatly enhanced with manure addition, increasing it from 32.6 to 97.7 mg P kg-1. NaOH-Pi was the largest extractable Pi fraction and ranged from 144.3 to 250.6 mg P kg-1 and 107.5 to 213.2 mg P kg-1 in the unamended and manure amended treatments, respectively. Dry matter yield and P uptake by maize grown in the glasshouse were highly and significantly (p = 0.05) correlated with the different P fractions in the soil. The correlations followed the order resin P (r = 0.85) > NaOH-Pi (r = 0.85) > NaHCO3-Pi (r = 0.84) >> biomass P (r = 0.56) for dry matter yield at 6 weeks after planting. At 12 weeks after planting, goat manure had iv highly significant effects on resin P and biomass P but had no effect on NaHCO3-Pi and NaOH–Pi. The combination of biomass P, resin P and NaHCO3-Pi explained 75.8 percent of the variation in dry matter yield of which 63.0 percent of the variation was explained by biomass P alone. The greatest increase in biomass P occurred when added P was co-applied with 5 or 10 tha-1 goat manure. The predictive equation for maize dry matter yield (DM) was: DM (g) = 1.897 biomass P + 0.645 resin P (r = 0.73). Resin P was the fraction that was most depleted due to plant uptake and decreased by 56 to 68 percent between the 6th week and the 12th week of sampling indicating that it played a greater role in supplying plant available P. The results therefore suggested that the use of goat manure may allow resource poor farmers to use lower levels of commercial phosphate fertilizers because of its effect to reduce soil P sorption. In addition, higher increases in biomass P due to manure addition observed at lower rates of added P indicated that goat manure has potential for enhancing bioavailability and fertilizer use efficiency of small inorganic P applications.

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