Very few sewage and industrial waste treatment effluents are free from microorganisms and proteins. Such discharges require further treatment by the receiving stream and consequently lower stream quality. The object of this investigation was to evaluate chlorinated solvent processes for the removal of microorganisms, proteins, and other substances from sewage and other wastes. Six different chlorinated solvents were added to different waste samples in the ratio (by volume) of five percent solvent and 95 percent waste, mixed and allowed to settle for a specified period of time. The efficiency of the solvent extraction process was evaluated in terms of reduction of suspended solids, biochemical oxygen demand, and by increased weight of residue separable by sedimentation. The results showed that the process produced the following effects on settled sewage. Suspended solids were reduced by 85 percent, the weight of residue separable by sedimentation was increased 33 percent, and the biochemical oxygen demand was reduced 49 percent. The process was less effective for the treatment of raw sewage, trickling filter effluent, sewage lagoon effluent, or for separation of activated sludge. The variables investigated were temperature, pH and the solvent waste system. Temperature and pH appeared to have negligible effects on the extraction efficiency. The solvents employed were; chloroform, ethylene dichloride, chlorobenzene, carbon tetrachloride, trichloroethane, and dichloroisopropyl ether. Solvents with low vapor pressures and wastes with low concentrations of suspended solids appeared to be the most efficient system. The addition of 20 percent of butanol (by weight) to trichloroethane appeared to increase the extraction efficiency of trichloroethane. Bacterial counts made indicated that the solvent extraction process was affecting better than 90 percent removal of microorganisms from the waste samples. More research will be needed to completely evaluate chlorinated solvent processes for the removal of microorganisms, proteins, and other substances from sewage and other wastes. / Master of Science

This investigation has led to the following conclusions: 1. Good removals of most bacterial species were observed. 2. Increased length of settling time increased the percent removal of pure cultures. 3. The solvent coagulation process worked best at a pH very near the pH produced by the bacteria during growth. 4. There was no advantage in changing from room temperature. S. proper surface active agents aided in the coagulation of bacteria in the solvent ooagulation process. 6. Almost all of the bacteria in suspension after the coagulation process were not viable. 7. Good removals were observed using the solvent coagulation process on mixed cultures. 8. The chlorinated solvent coagulation process shows promise for commercial operations. / Master of Science

This study was undertaken to examine the polymer mixing requirements for sludge dewatering with a belt filter press. This involved correlating full-scale field studies to small scale laboratory testing. Bench testing involved the use of a high-speed mixer and two sludge dewatering response tests: the capillary suction time test and the time-to filter test. Full-scale testing measured the belt press response to belt speed, sludge throughput, and polymer dose. Data indicated that the conditioning and dewatering scheme of the three belt filter presses was a low shear, low total mixing energy operation. The Gt, or total mixing energy, of these operations was in the range of 8,000-12,000. Optimal dose predicted by the bench-scale testing correlated well to the optimal dose for maximum cake solids coming off the belt filter press. Also, the amount of water removed from the sludge with the belt press was largely a function of the type of solids present in the sludge and less of a function of the number of rollers or residence time in the press. / Master of Science

The role of metal cations in enhanced biological phosphorus removal (EBPR) from wastewater by activated sludge was investigated. Potassium and magnesium were simultaneously required for efficient EBPR. Neither potassium nor magnesium could induce enhanced phosphorus uptake on its own. Cations were co-transported with phosphorus during anaerobic release and aerobic uptake. With every mole of phosphorus, between 0.23 and 0.43 moles of potassium and between 0.25 and 0.36 moles of magnesium were co-transported. Calcium appeared to be involved in EBPR to a limited extent, and did not seem to chemically co-precipitate with phosphorus. For every gram of chemical oxygen demand (COD) consumed by the sludge in the anaerobic zone of the experimental systems, 0.22 grams of phosphorus were released at a 15 d mean cell residence time and 20°C. Approximately 20 mgCOD/L were taken up by the sludge before any phosphorus was released. Phosphorus release could be described by first order kinetics. Phosphorus uptake under aerobic conditions could also be described by first order kinetics. The total phosphorus uptake in the anoxic and aerobic zones of the experimental systems was proportional to the total phosphorus release in the anaerobic zone. For every gram of phosphorus released, between 1.1 and 1.2 grams of phosphorus were taken up by the sludge regardless of the operating conditions. Phosphorus uptake by the sludge in the aerobic phase was hindered by the presence of acetate in solution. Uptake commenced only after all of the available acetate was first consumed by the sludge. Distilled water, 0.85 percent sodium chloride, and 5 mM and 50 mM ethylene diamine tetra-acetic acid were used to extract chemically precipitated phosphorus from EBPR sludge. Each of the washing media seemed to cause some cell lysis, suggested by the extraction of non-reactive phosphorus. The duration of wash seemed to affect the extent of cell lysis. Phosphorus fractionation extracts were assayed for deoxyribonucleic acid to determine whether cell lysis occurred. The assay was apparently not affected by the contents of the sludge supernatant. / Ph. D.

No description available.

Submitted in fulfilment of the requirements of the degree of Master of Engineering - Chemical, Durban University of Technology, Durban, South Africa, 2015. / Industrial wastewater containing organic compounds and/or substances is an increasing problem due to its increasing toxic threat to humans and the environment. The removal of organic compounds has become an imperative issue due to stringent measures that are introduced by the Department of Environmental Affairs in South Africa to enforce regulations concerning wastes that emanate from petrochemical industries. Thus, wastewater containing these compounds must be well understood so as to device adequate treatment processes. In this study, the adsorptive capacity of PAD 910 polystyrenic resin originating from China and granular activated carbon (GAC) was evaluated for the removal of benzene, toluene, ethylbenzene and isomers of xylene (BTEX) from an aqueous solution. Batch studies were performed to evaluate the effects of various experimental parameters such as mixing strength, contact time, internal diffusion, adsorbates and initial concentration on the removal of the BTEX compounds. The experiments were conducted at the mixing strength of 180 rpm, in order to comfortably assume negligible external diffusion. The equilibrium isotherms for the adsorption of the adsorbates on the PAD 910 polystyrenic resin were analyzed by the Langmuir, Freundlich and linearized Dubinin-Radushkevich models at a pH of 5.86. The Langmuir model fitted the data adequately; this result was supported by the work done by Site (2001) which concluded that the Langmuir is the most practical model in representing the adsorption of aromatic compounds. The Langmuir model indicated that resin has the highest adsorption capacity of 79.44 mg/g and GAC has 66.2 mg/g. Resin was found to adsorb 98% of benzene, 88% of toluene, 59% of ethylbenzene, 84% m-;p-xylene and 90% o-xylene at an initial concentration of 14.47 mg/l. BTEX adsorption was a two-stage process: a short, fast initial period then followed by a longer, slow period corresponding to the intra-particle diffusion of BTEX molecules in macropores and micropores. The adsorption capacity was determined by total surface area accessible to BTEX and the availability of active surface chemical groups. The dependence of adsorption capacity on the surface of the two adsorbents and temperature was observed, suggesting the chemical nature of the BTEX adsorption. The interaction between BTEX/activated carbon was however weak and energetically similar to that of hydrogen bonds. Generally, BTEX adsorption was an exothermic process that combined physisorption and chemisorption. The PAD 910 polystyrenic resin had a greater specific surface area (SSA) of 1040 m2/g which yielded in higher capacity compared to GAC which had a low SSA of 930 m2/g. The normalized adsorption capacity was found to be higher for PAD 910 polystyrenic resin than GAC (0.66 and 0.27 mg/m2 respectively) which suggests that the resin has a good potential of the adsorbent for removing BTEX compound compared to GAC. Fixed bed columns were used to evaluate the dynamic adsorption behaviour of BTEX/PAD 910 polystyrenic resin through a dynamic column approach. The performance of small-scale fixed bed columns, each containing PAD 910 polystyrenic resin and the other containing GAC were evaluated using 14.47 mg/L of BTEX concentration. The columns with 32 mm diameter, studied bed depths of 40, 80 and 120 mm and flow rate of 6 ml/min were used in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and design parameters like adsorption capacity, adsorption rate and service time at 20% and 60% breakthrough. BDST was also used to predict the service times of columns operated under different influent concentrations and flow rates to produce theoretical values that were compared to the experimental values. Adsorption model by Dubinin and colleagues (Dubinin, 1960), based on the theory of volume filling micropores was used to fit the measured adsorption isotherms. Agreement between the modelled and experimental results for GAC and PAD 910 polystyrenic resin using Dubinin-Radushkevich equation generally improved with increasing the surface area and produced reasonable fits of the adsorption isotherms for both GAC and PAD 910 polystyrenic resin. Granular activated carbon had a lesser performance compared to the PAD 910 polystyrenic resin, in terms of kinetic studies, and this finding was attributed to the pore structure which made accessibility of BTEX molecules more difficult in this study. The results indicate that PAD 910 polystyrenic resin show potential as an adsorbent for removing low concentrations of BTEX from wastewater. It is suggested that necessary treatment of GAC might improve the performance of this adsorbent by creating more mesopore volume and fraction which is essential to enhance adsorption rate. A substantial different SSA could be achieved through high porosity development in GAC by using templating method with a higher potassium hydroxide mixture ratio.

Thesis (MScEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Urine contains up to 80% of nitrogen, 50 % of phosphates and 90 % of potassium of the total load in domestic wastewater but makes up less than 1% of the total volume (Larsen et al., 1996). The source separation and separate treatment of this concentrated waste stream can have various downstream advantages on wastewater infrastructure and treated effluent quality. The handling of undiluted source separated urine however poses various challenges from the origin onward. The urine has to be transported to a point of discharge and ultimately has to be treated in order to remove the high loads of organics and nutrients. Wilsenach (2006) proposed onsite treatment of source separated urine in a sequencing batch reactor before discharging it into the sewer system. This study focused on the treatment of urine in a sequencing batch reactor (SBR) primarily for removal of nitrogen through biological nitrification-denitrification. The aim of the study was to determine nitrification and denitrification kinetics of undiluted urine as well as quantification of the stoichiometric reactions. A further objective was to develop a mathematical model for nitrification and denitrification of urine using experimental data from the SBR. The SBR was operated in 24 hour cycles consisting of an anoxic denitrification phase and an aerobic nitrification phase. The sludge age and hydraulic retention time was maintained at 20 days. pH was controlled through influent urine during volume exchanges. Undiluted urine for the study was obtained from a source separation system at an office at the CSIR campus in Stellenbosch. Conditions in the reactor were monitored by online temperature, pH and ORP probes. The OUR of the system was also measured online. One of the main challenges in the biological treatment of undiluted urine was the inhibiting effect thereof on nitrification rate. The anoxic mass fraction was therefore limited to 17 % in order to allow longer aerobic phases and compensate for the slow nitrification rates. Volume exchanges were also limited to 5% of the reactor volume in order to maintain pH within optimal range. Samples from the reactor were analysed for TKN, FSA-N, nitrite-N, nitrate-N and COD. From the analytical results it was concluded that ammonia oxidising organisms and nitrite oxidising organism were inhibited as significant concentrations of ammonia-N and nitrite-N were present in the effluent. It was also concluded that nitrite oxidising organisms were more severely inhibited than ammonia oxidising organisms as nitrate-N was present in very low concentrations in the effluent and in some instances not present at all. Ultimately the experimental system was capable of converting 66% of FSA-N to nitrite- N/nitrate-N of which 44% was converted to nitrogen gas. On average 48% of COD was removed. A mathematical model was developed in spreadsheet form using a time step integration method. The model was calibrated with measured online data from the SBR and evaluated by comparing the output with analytical results. Biomass in the model was devised into three groups, namely heterotrophic organisms, autotrophic ammonia oxidisers (AAO) and autotrophic nitrite oxidisers (ANO). It was found that biomass fractionation into these three groups of 40% heterotrophs, 30% AAO and 30% ANO produced best results. The model was capable of reproducing the general trends of changes in substrate for the various organism groups as well as OUR. The accuracy of the results however varies and nearexact results were not always achievable. The model has some imperfections and limitations but provides a basis for future work.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Submitted in fulfillment for the requirements for the Degree of Doctor of Technology: Biotechnology, Durban University of Technology, 2012. / Nitrification is a crucial step in biological nutrient removal (BNR) processes, mostly carried out by a group of nitrifying bacteria which includes ammonia-oxidising bacteria (AOB) and nitrite-oxidising bacteria (NOB). Nitrification failure has proven to be a common operational problem in full-scale wastewater treatment plants (WWTP) since nitrifying bacteria are very sensitive to sudden changes in environmental or plant operating conditions. The current investigation was carried out to advance our understanding of the distribution of nitrifying bacterial populations and their performance at three different BNR plants in KwaZulu-Natal, South Africa. The latest molecular techniques such as fluorescent in situ hybridisation (FISH)-confocal scanning laser microscopy (CSLM), polymerase chain reaction (PCR) and real-time quantitative PCR (Q-PCR) were applied to detect and quantify nitrifying bacteria. When using FISH to target the nitrifying population, it necessitated optimising pre-treatment protocols of the samples to improve accuracy during quantification. Sonication was found to be the superior method of dispersion based on the least disruption of nitrifier cell integrity, irrespective of the sludge type. The effect of plant configurations and wastewater characteristics on the distribution of the nitrifying bacterial population and subsequently on the nitrification performance was evaluated using FISH and PCR. FISH results revealed the dominance of Nitrosomonas (AOB), Nitrobacter (NOB) and Nitrospira (NOB) for all BNR plants. The 16S rRNA analysis of PCR products using genus-specific primers, revealed the presence of more than one species of the same group at these plants. Nitrosomonas spp. including Nitrosomonas halophila, Nitrosomonas eutropha, Nitrosomonas europaea, Nitrosomonas aestuarii and an unidentified Nitrosomonas spp. were found to dominate among the AOB and Nitrobacter vulgaris, Nitrobacter alkalicus, Nitrobacter hamburgensis and an unidentified Nitrobacter spp. were the dominant species for NOB. Among these species, Nitrosomonas aestuarii, Nitrosomonas europaea, Nitrobacter hamburgensis were detected only from the industrial wastewater samples. The efficiency of two commonly used techniques viz., FISH and Q-PCR for the detection of nitrifiers from WWTP were also studied and compared, specifically targeting Nitrobacter sp. Even though there were slight variations in the quantification results, changes in the Nitrobacter community at these plants were consistent for both FISH and Q-PCR results. Both techniques have their own limitations and advantages. This study has helped to add to the platform of understanding the distribution and activity of nitrifying bacteria by correlating population dynamics with the operational parameters at full-scale level. The observations made in this study will assist researchers and engineers to minimise future nitrification failure at full-scale BNR plants. This study also confirmed the highly complex activities of wastewater treatment processes, which is dependant on a number of factors. Specific AOB or NOB predominant in wastewater rather suggests that the wastewater type and characteristics may contribute to significantly different microbial environments. Among the AOB, Nitrosomonas dominated at all BNR plants throughout the study period and for NOB both Nitrobacter and Nitrospira were found in significant numbers but their dominance varied across the plants. These dissimilar, distinct distribution patterns could be attributed to their environment which in turn impacted on the nitrification performance of the system. It was also noted that the co-existence of more than one group of these communities at the same plant could help the plant escape complete functional failures such as nitrification, due to sudden changes in temperature and substrate concentrations, as this function can be performed by different groups. Although it would have been meritorious to conduct a nitrogen balance in this study, this was not possible since the research focused on full-scale systems. / National Research Foundation / D