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Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: J. Thomas Sims, Agriculture and Natural Resources. Includes bibliographical references.

Five different combinations of Hydraulic Retention Times (HRT) and temperatures were used in a two stage (feed and test reactor) Autothermal Thermophilic Aerobic Digestion System to assess the impact of these parameters on the production of odorous gases. The gases monitored were hydrogen sulphide, dimethyl sulphide, methyl mercaptan, ammonia, and amines. Other liquid parameters were also monitored in order to better understand the impacts of temperature and HRT. These parameters are total solids content, volatile solids content, volatile solids destruction, specific oxygen uptake rate, alkalinity, ammonia concentration, and pH. In order to assess the character of the sludge and understand the digestion process the carbohydrate, fat, and protein content were also measured in the inputs and in the test reactor. It was found that all of the odorous compounds measured were affected by stage of digestion and temperature more than by HRT. Of the five compounds monitored, none were affected by changes in the HRT of the test reactor. However, the concentrations measured in the feed and test reactors were often a degree of magnitude apart. The reduced sulphur compounds (hydrogen sulphide, methyl mercaptan, and dimethyl sulphide) were found in higher concentrations in the feed reactor than in the test reactor; whereas ammonia and amines were found in much higher concentrations in the test reactor than in the feed reactor. Also, ammonia concentrations were significantly higher in both reactors when the temperature was higher; and amine concentration was higher in the test reactor when the temperature was higher. One set of tests for volatile fatty acid concentration was also undertaken. While breakdown of the carbohydrates and fats occurred throughout the process, proteins were broken down into their amino acids, releasing reduced sulphur compounds in the feed reactor and then deaminated, releasing ammonia and amines in the test reactor.

Includes bibliographical references.

Five different combinations of Hydraulic Retention Times (HRT) and temperatures were used in a two stage (feed and test reactor) Autothermal Thermophilic Aerobic Digestion System to assess the impact of these parameters on the production of odorous gases. The gases monitored were hydrogen sulphide, dimethyl sulphide, methyl mercaptan, ammonia, and amines. Other liquid parameters were also monitored in order to better understand the impacts of temperature and HRT. These parameters are total solids content, volatile solids content, volatile solids destruction, specific oxygen uptake rate, alkalinity, ammonia concentration, and pH. In order to assess the character of the sludge and understand the digestion process the carbohydrate, fat, and protein content were also measured in the inputs and in the test reactor. It was found that all of the odorous compounds measured were affected by stage of digestion and temperature more than by HRT. Of the five compounds monitored, none were affected by changes in the HRT of the test reactor. However, the concentrations measured in the feed and test reactors were often a degree of magnitude apart. The reduced sulphur compounds (hydrogen sulphide, methyl mercaptan, and dimethyl sulphide) were found in higher concentrations in the feed reactor than in the test reactor; whereas ammonia and amines were found in much higher concentrations in the test reactor than in the feed reactor. Also, ammonia concentrations were significantly higher in both reactors when the temperature was higher; and amine concentration was higher in the test reactor when the temperature was higher. One set of tests for volatile fatty acid concentration was also undertaken. While breakdown of the carbohydrates and fats occurred throughout the process, proteins were broken down into their amino acids, releasing reduced sulphur compounds in the feed reactor and then deaminated, releasing ammonia and amines in the test reactor.

The biological treatment of pulp and paper mills effluents results in the production of waste secondary sludge which is hard and costly to dewater and dispose. Secondary sludge, which is structurally comparable to the municipal sewage sludge, is composed of microbial cells, organic woody materials, and ash. In this work, the use of this waste biosolid as renewable and cost-cutting filler in the composite industry is proposed. Moreover, the effect of enzymatic treatment of the waste biosolid on the final properties of the manufactured biocomposite is studied. The high protein content of the secondary sludge (35 ± 5%) and the surface thermodynamics measured by Inverse Gas chromatography (IGC) led us to choose Nylon 11 as the main polymeric matrix. The biocomposites samples produced by compounding and injection molding of different mixtures of dried secondary sludge and Nylon were tested. The results of mechanical strength tests showed that a 10% sludge content does not lead to any significant deterioration of either tensile or flexural strengths. Therefore, it is concluded that the secondary sludge may be used as filler to reduce the cost while maintaining the mechanical properties of Nylon. Enzymatic modification of the waste biosolid to advance its application from cheapening filler to reinforcing filler has also been proposed in this work. Lipase and laccase utilized for the modification of the sludge in order to reduce the hydrophobicity and increase the molecular weight, respectively. Lipase application did not lead to any significant changes in either tensile or flexural strengths. This is attributed to the rather low content of lipids in the sludge. On the other hand, enzymatic modification of the sludge by laccase which increases the molecular weight of the existing lignins, resulted in significant improvement of the flexural strength of the manufactured biocomposite.