Organic carbon and nitrogen content in low-strength wastewaters can be removed by conventional aerobic processes such as Modified Ludzak Ettinger (MLE), but these treatment methods are not appropriate for treating strong wastewaters. Treatment of highly polluted effluents from slaughterhouse, food processing, brewery, dairy, landfill leachates, etc., which are rich in organic matter and nutrients requires specific considerations. The main removal pathways in the aerobic processes are bacterial assimilation and complete nitrification-denitrification for nitrogen content removal which is accompanied by organic carbon removal during this process. Various biological aerobic treatment processes and operations have been tried in the past to effectively treat strong streams, but high energy requirement and sludge production are serious drawbacks. Anaerobic digestion (AD) is the best alternative to the aerobic processes for treatment of strong wastewaters but biological nutrient removal is not possible, and needs further treatment. In high-strength wastewater treatment, neither aerobic nor anaerobic treatment methods alone as a single-process can produce treated effluents complying with discharge standards. Therefore, existing conventional technologies for treatment of highly polluted streams are combined systems. These conventional combined systems are a pair of at least two separate processes in series. Most of the combined systems are applying the AD as a head system which is followed by a polishing aerobic process such as conventional activated sludge. Synchronizing two different processes in a series in combined systems is expensive and complicated with intensive operation and maintenance requirements. Hence, in order to prevail these difficulties, it is paramount to develop an efficient and less expensive single-process technology with simple operation and maintenance. In this thesis, a conventional MLE system as a single-process was modified for treating highly polluted wastewaters, with a performance similar to the combined systems. This modified system is referred to throughout the thesis as SAO/PND (Simultaneous Anaerobic Oxidation/Partial Nitrification–Denitrification). After several unsuccessful modifications were tried, the main successful modifications were increasing the hydraulic retention time (HRT) in the pre-anoxic reactor, and decreasing the solids retention time (SRT) to create favorable conditions for anaerobic oxidation and partial nitrification-denitrification. A laboratory-scale of SAO/PND was used to conduct the experiments in this research. SAO/PND looks like the MLE process regarding the reactor configurations and recycle and return lines. Ammonia concentrations above 150 mg/L can be toxic for the MLE system, but SAO/PND improves the situation so that ammonia concentration is not toxic until close to 290 mg/L. Another issue with MLE process is that it requires high amounts of oxygen and alkalinity which results in high amounts of sludge production. But, SAO/PND produces less sludge, and does not need high amounts of oxygen and alkalinity. The results showed more than 95% chemical oxygen demand (COD) and 90% total inorganic nitrogen (TIN) removal from synthetic wastewater, respectively, in our laboratory environment. In addition, volumetric design loading rates determined as 11.80 kg COD/(m3.d) and 0.63 kg TIN/(m3.d) with synthetic solution as a feed. Furthermore, the results showed high performance of the system in treating dairy and brewery industry effluents. In this modified single-process system, organic carbon was removed through anaerobic oxidation, assimilation, P–uptake by polyphosphate accumulating organisms (PAOs) and denitrifying PAOs (DPAOs), aerobic heterotrophs, and denitrification by DPAOs and denitrifying ordinary heterotrophic organisms (OHOs). Nitrogen content removal mechanisms were assimilation, partial nitrification–denitrification, anaerobic ammonium oxidation (anammox), and small portion uncharacterized processes. 95% and 90% less oxygen requirements along with 60% and 44% less sludge production compared to the conventional aerobic processes and conventional combined systems, respectively, resulted in significant potential cost savings by this modified system. Finally, the applied modified single-process system in this thesis is found as a sustainable, robust, cost-effective, and small footprint process with less intensive operation and maintenance requirements which will yield new insights into the design of treating highly polluted streams in the future.

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Surface and subsoil samples were collected from agriculturally important soils of Coastal Plain, Piedmont and Ridge and Valley regions of Virginia for the purpose of determining the contribution of different soil N fractions to plant available N. Soil samples were analyzed for exchangeable and non-exchangeable NH₄⁺-N, NO₃⁻-N, total N, and organic matter contents. The samples were also subjected to the anaerobic incubation procedure as an index of organic N availability. Plant available N was measured by N uptake of successive wheat crops grown in the greenhouse. Multiple linear regression models for different groups of samples were used to determine the contribution of the different soil N fractions to the plant available N supply, and to predict N uptake by wheat. Best models were selected considering fit, significance of the regression coefficients, and predictive ability. Due to the high correlation among the different soil N fractions, important collinearity was present and affected the linear models. These effects were reduced by utilizing biased techniques. All the soils provided significant amounts of N to the wheat in both the first and second crops. Exchangeable NH₄⁺-N and NO₃⁻-N were the major initial sources of plant available N. Non-exchangeable NH₄⁺-N was also a significant contributor to the plant available N supply for most soils. The results of the biological and chemical indices of organic N availability were highly correlated among each other, and with plant N uptake by the first and second wheat crops. Plant N uptake was associated with the variation observed in the different soil N fractions, indicating that wheat is a good indicator crop for plant N availability experiments. The procedures used to detect and combat collinearity were effective in producing more stable models with better predictive ability. Further research should be conducted under field conditions to study the contribution of non-exchangeable NH₄⁺-N to plant N availability. / M.S.

Call number: LD2668 .T4 1984 R327 / Master of Science

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Transition state theory was applied to the nitrification process in soil-water systems, and a computerized, theoretical rate model was developed to include NH₄⁺ and 0₂ concentrations, pH, temperature, moisture content, and local differences in nitrifying capacities of Nitrosomonas bacteria. The model was restricted to enriched calcareous soils thus simplifying the application of basic physicochemical principles. Experimental rate data from an agricultural and a native desert soil provided verification of a zero order reaction for nitrification with respect to NH₄⁺ concentrations above a certain saturation level, as previously reported. The saturation concentration in soils was found to be about 1.0 to 5.0 ppm. A theoretical linear relationship between activation energy and ionic strength was confirmed by application of the above data. However, each local population of nitrifiers tended to display different values for the slope and intercept of the linear relationship. The structure of the activated complex for NH₄⁺ oxidation to NO₂⁻ was determined to be more like NH2OH or NH₄⁺ than NO₂⁻. As a first approximation, the NH₂OH activated complex was included in the rate model. The equation form for the equilibrium between the reactants and the activated complex was found to differ from the stoichiometric reaction between NH₄⁺ and O₂ to form NH₂OH. The equilibrium expression was found to be more closely approximated by the relationship, 2 NH₄⁺ + O₂ ≶ (ACTIVATED COMPLEX) + + H⁺. A method was developed to compute soil pH values as a function of moisture content. Verification was obtained by using data obtained from the agricultural and native desert soils, including cases where samples were acidified. The calculated pH values were used in the nitrification rate model. Further verification of the model was obtained using data from the literature for two soils from the Northern Great Plains. Data pairing of observed and predicted rates for these soils yielded R values of 0.944 and 0.940. The rate model was programmed in FORTRAN IV computer language and designed to operate in conjunction with existing computer models. Thus, this relatively sophisticated model may be applied to field simulation studies with a minimum of adaptive procedures. The model should aid in obtaining reliable predictions of NO₃⁻ formation and movement under a wide range of field conditions.

Clinoptilolite zeolite has a theoretical cation exchange capacity of 2.25 moles of charge kg⁻¹, and a rigid three-dimensional lattice riddled with angstrom-sized tunnels, and interconnected voids, in which water and exchangable cations are held. The hypothesis was that clinoptilolite had the facility to preferentially and internally sorb NH₄⁺, where it would be physically protected from microbial nitrification. Hence nitrification rates would be decreased and plant N-fertilizer use efficiency increased. Exchange capacities of clinoptilolite determined at 30°C by saturation/desorption for NH₄⁺, K⁺ and Na⁺ were approximately 2.00 moles of charge kg⁻¹, while capacities for Ca²⁺ and Mg²⁺ were 1.53 and 0.97 respectively. On this basis three site groups were identified: those accessible to all cations studied, sites accessible to all cations but Mg²⁺ and sites only accessible to NH₄⁺, K⁺ and Na⁺. Equilibrium isotherms were used to determine selectivity of site groups at 30°C. Consideration of site accessibilities and selectivities indicate an overall preference of clinoptilolite of: K⁺ > NH₄⁺ > Na⁺ = Ca²⁺ > Mg²⁺. Notably, the plant macronutrient cations, K⁺ and NH₄⁺, are preferentially sorbed. Nitrification of NH₄⁺ on clinoptilolite amended sands incubated at 20% volumetric moisture capacities, was studied in the laboratory. Treatments were washed mortar sand amended with 0, 5 and 10% clinoptilolite by volume and 2.38 and 3.57 moles of NH₄⁺ m⁻³ of sand-clinoptilolite mix. Nitrification was evaluated by monitoring NH₄⁺ loss. Rates of nitrification decreased with increasing clinoptilolite amendment and decreased with N-fertilizer initially applied. The effect of clinoptilolite in slowing nitrification was more pronounced at higher initial NH₄⁺-fertilizer application. The hypothesis that internally sorbed NH₄⁺ in clinoptilolite is physically protected from microbes resulting in decreased nitrification rates was confirmed. The effect of clinoptilolite on N-use efficiency of creeping bentgrass was studied in a field trial. Factorial treatments included washed mortar sand amended with 0, 5 and 10% clinoptilolite by volume and 25, 50 and 75 kg of N ha⁻¹ growing month⁻¹. Approximately 45% of applied N was harvested in clippings from 10% clinoptilolite amended sand in contrast to 36% N recovery on 100 % sand. This supports the hypothesis of improved plant N-fertilizer use efficiency on clinoptilolite amended sand.

Thesis. 1978. Sc.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 307-314. / Sc.D.

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