Thesis (Ph.D.(Chemical Engineering))--University of Pretoria, 2008. / Summary in English. Includes bibliographical references.

Laboratory lysimeters were used to investigate the behaviour, over time, of a humid west coast forest soil under intermittent primary municipal waste water irrigation. Mineral soil packed to a depth of 69 cm and to a uniform density of about 0.9 gm per cm³ was covered with a forest floor 9 cm thick. Sintered glass bead tensiometers were used to gauge the water potential distributions in the soil lysimeters. Irrigation and drainage systems were designed to maintain constant rates of waste water application and facilitate measurement of drainage rates. Two groups of soil lysimeters each with triplicate samples, were loaded with waste water at the rates of 0.23 cm per day ( 37 cm³ per day ) and 0.47 cm per day ( 75 cm³ per day ) for a period of 9 months. The soil lysimeters were incubated at a temperature of about 15.5 degrees Centigrade. The total amounts of nitrogen added to both groups of soil lysimeters were 223.7 gm and 436.9 gm or equivalent to 1.4 % and 2.7 % of the total nitrogen of the original soil, respectively. Renovations of wastewater in terms of nitrogen were 75 % and 43 % with respect to the two groups of soil lysimeters. Renovations in terms of phosphorus were more than 99 % in both groups of soil lysimeters. Retention of nutrients by the soil was increased with time under favourable aerobic conditions. Uptake of nutrients by vegetation in the field would minimize leaching losses. Results from this experiment indicated no significant changes in the physical and chemical behaviour of the soils. Proper design of the waste water irrigation system in terms of loading would maximize the efficiency of renovation without deteriorating the behaviour of the soils. / Land and Food Systems, Faculty of / Graduate

A lab-scale study of anoxic-aerobic digestion of waste activated sludge was performed, using 6 litre digesters, and operated in a semi - continuous (fed-once-a-day) manner with solids retention times (SRTs) of 20, 15 and 10 days and mixed-liquor temperatures of 20 °C and 10 °C. Raw sludge was obtained from a pilot-scale biological phosphorus removal facility operating at U.B.C. Fresh sludge was obtained daily and digested by three different digestion modes: anoxic-aerobic, aerobic with lime addition and aerobic. Two aerobic control digesters were run in parallel with the anoxic-aerobic digesters. One of the aerobic digesters received a daily dose of lime slurry. All three digesters were operated under identical conditions (except for the cycling of air supply to the anoxic-aerobic digesters) so that direct comparison could be made between the three digestion modes. Comparisons were made on the basis of five main parameters related to: (1) digestion kinetics, (2) digested sludge characteristics, (3) supernatant quality, (4) ORP monitoring, and (5) an overall rating system. Percent volatile suspended solids (VSS) reduction was used as one performance variable. Despite using only 42 percent of the air required by the two controls, anoxic-aerobic digestion showed comparable percent VSS reductions. All three digestion modes showed increased solids reduction with increasing SRT and temperature. There was a linear relationship between percent TVSS and the product of SRT and temperature. All three digestion modes had a propensity to retain their percent nitrogen and phosphorus within their solids. However, with respect to retaining phosphorus, the aerobic controls were the least effective. Anoxic-aerobic digestion maintained neutral mixed-liquor pH (MLpH) throughout. Lime controls were maintained at MLpH close to neutral. Aerobic digestion, in general, resulted in MLpH levels below 5.0, however, there were periods when the MLpH of the aerobic digesters varied widely between 4.2 and 6.8. Supernatant quality was superior for the anoxic-aerobic digesters. Due to the incorporation of non-aerated periods, there was almost 100 percent denitrification of nitrates produced during the aerated time. This nitrification-denitrification resulted in very low soluble nitrogen levels in the effluent, as well as considerable removal of nitrogen gas. Neither of the controls showed this ability. The lime and aerobic controls produced high levels of effluent nitrates, as well as occasional measurements of ammonia and nitrite. Phosphorus levels were lowest for the lime control and anoxic-aerobic digesters. Presumably, due to reduced pH levels, the soluble phosphorus levels from the aerobic digesters were 2 to 3 times those in the lime or anoxic-aerobic digesters. Alkalinity was conserved in the anoxic-aerobic digesters as well as the lime control. However, the purely aerobic digesters consumed alkalinity until very little buffering capacity remained. Oxidation-reduction potential (ORP) was used as a means of monitoring the anoxic-aerobic digesters on a real time basis. ORP was particularly useful during the non-aerated periods, due to the fact that, at those times, dissolved oxygen was undetectable. Characteristic real time ORP profiles were revealed. Slope changes correlated well with events of theoretical and engineering interest; the' disappearance of ammonia and nitrates, as well as the (dis)appearance of detectable dissolved oxygen, could be predicted by these slope changes. As a result of the findings, ORP may prove to be an ideal parameter for the control of the anoxic-aerobic digestion process. Finally, an overall rating system was developed. The results of this study suggest that, for the digestion of waste activated sludge, anoxic-aerobic digestion out-performed both lime-control and conventional digestion modes. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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

The current pressure on water bodies is a structural problem that may compromise the satisfaction of future water demand and the good status of the natural environment. Activities such as wastewater reuse or desalination provide an additional source of water resources to meet demand without the need to increase natural water abstractions. In addition, reuse also contributes to improving water quality by limiting abstractions and reducing discharges. However, reuse has not been widespread as a source of supply in resource-rich contexts. In resource-abundant areas, the high cost of reusing water is a strong disincentive to its use, which puts the focus on reducing pollution through discharge without assessing the potential of reuse as an additional source of resources. The use of reclaimed water has a great margin for development that should be exploited in the coming years to obtain a guarantee of supply and an improvement in the environmental quality of water in the current context of increasing scarcity. However, the financial and environmental situation of reuse requires the involvement of the public sector. In this work, two instruments with the potential to facilitate the development of reuse have been studied. The first of these is photovoltaic self-consumption, in order to reduce the cost of energy consumption of wastewater treatment plants, given that this is their main financial operating cost. This possibility, however, has shown little capacity to reduce these costs since, except in the case of the floating photovoltaic installation, the cost of electricity from self-consumption is higher or similar to the market price. If we consider the reduction of greenhouse gas emissions derived from self-consumption, this alternative is much more competitive. The situation is, once again, of an activity that presents financial losses and environmental benefits derived from the current excess of emissions. The responsibility lies with the public sector in the same way as in the case of reuse. Water tariffs, as one of the main revenues from water treatment, is an instrument that can be evaluated with a view to increasing revenues through an increase in the price of water. The results obtained show large differences in the impact of such an increase depending on the region but make it clear that the potential for additional revenue from this possibility is small. This analysis has also shown that there is a problem in the current tariffs that reduces their effectiveness by not valuing the type of household. The problem lies not in the structure of the tariff or the number of household members, but in the characteristics of the household. By not taking these into account and calculating the bill without these details, the tariffs are not fully effective. In conclusion, both reuse and photovoltaic self-consumption are beneficial activities for society, but the financial costs involved in their implementation require the involvement of a public sector with a reduced capacity to increase current revenues.

The objectives of this report was to study the existing literature and data of residential graywater treatment and disposal systems and their possible applications and environmental impacts in Florida. The report addresses mainly (1) the definition of graywater quantity and quality, (2) the evaluation of proposed graywater treatment systems for possible reuse and disposal, (3) the impact of residential graywater systems on existing and proposed wastewater treatment plants, and (4) the possible impacts on groundwater and surface water environment. The report also presents some preliminary residential graywater treatment and disposal system designs including expected treatment efficiencies and cost. It should be cautioned that the proposed designs and efficiencies are based on limited operational or test data, and a great amount of field data was obtained for blackwater septic tanks. Finally, it recommended that additional laboratory, field and operational testing is required to evaluate system design parameters and possible environmental impacts for the Florida Environment.

Thesis (M. Sc.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 59-62).

Thesis (Ph.D.)--University of Western Australia, 2008.

Thesis (M. Sc. (Soil Science)) -- University of Limpopo, 2019 / Water scarcity poses significant risks to global food security. The use of treated wastewater for irrigation could be a sustainable remedy for water scarcity in arid to semi-arid regions. Furthermore, it has been the most readily available source of water which can serve as an adaptation strategy to shortage of irrigation water. The objectives of the study were to determine (1) whether different disposal points following wastewater treatment could have effects on the quality of treated wastewater used for irrigation at the University of Limpopo (UL) experimental farm and (2) the response of selected critical nutrients, microbial and enzyme activities on soils irrigated with treated wastewater at the UL Experimental Farm. Water samples were collected monthly at three disposal points, namely, the exit point of treated wastewater from the treatment plant (Pond 16), the entry point into the night-dam and the exit point from the night-dam at the UL Experimental Farm. The water samples were analysed for pH, electrical conductivity (EC), sodium (Na), nitrate (NO3-), phosphate (PO42-), sulphate (SO42-), salinity, magnesium (Mg), calcium (Ca), potassium (K), chlorine (Cl), total dissolved solids (TDS), total soluble salts (TSS), lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn), Ascaris lumbricoides, Escherichia coli, Shigella spp., Salmonella spp. and Vibrio cholera. A field experiment was conducted on a separate 4-ha virgin field (VF), cultivated field (CF) and fallowed field (FF), with soil samples collected from 0- 5, 5-15 and 15-30 cm soil depth in each field and analysed for pH, EC, mineralisable P, NH4+, NO3-, organic carbon (OC), active carbon (AC), potential mineralized nitrogen (PMN), fluorescein diacetate (FDA) and phosphatase (PTS) enzyme activity. All data were subjected to ANOVA using Statistix 10.1. The treated wastewater had, at the three sampling points, significantly different EC, Na, NO3-, PO42-, SO42-, Cu, Zn, Shigella spp., V. cholerae, A. lumbricoides and E. coli, whereas salinity, pH, Mg, Ca, K, Cl and Cd were not affected by the sampling point. Generally, the night-dam entry and exit points had significant increases in PO42-, K and Ca when compared to Pond 16 exit. In contrast, the flow of wastewater from Pond 16 through the furrow to the entry and exit of the night-dam resulted in decreases of Na, NO3- and Cl. The exit point of water from the night-dam at UL Experimental Farm had the least harmful materials, rendering it the safest point with the best water quality for irrigation. In the field study, NH4+, NO3- and PMN were significantly different in soil depth. However, NO3- field × depth interaction effects were not significantly different. In contrast to all soil parameters, FDA and PTS activity for both soil depth and field × depth interaction effects were highly significantly different. The EC and pH were not affected by soil depth or field type. The negative effects of treated wastewater were mainly observed in the cultivated field. In conclusion, treated wastewater with fallowing could be used as the best approach to overcome water shortages, with the uses having the potential to reduce the need to apply high synthetic chemical fertilisers. Keywords: water reuse, disposal points, essential nutrients, microbial activities

Submitted in fulfillment of the academic requirements for the Master’s Degree in Technology: Chemical Engineering, Durban University of Technology. Durban. South Africa, 2015. / Increased public concern over health and the environment, the need to expand existing wastewater treatment plants due to population increase, and increasingly stringent discharge requirements, have created a need for new innovative technologies that can generate high quality effluent at affordable cost for primary and secondary re-use. The membrane biological reactor (MBR) process is one of the innovative technologies that warrant consideration as a treatment alternative where high quality effluent and/or footprint limitations are a prime consideration. MBR processes have been applied for the treatment of industrial effluent for over ten years (Harrhoff, 1990). In this process, ultrafiltration or microfiltration membranes separate the treated water from the mixed liquor, replacing the secondary settling tanks of the conventional activated sludge process. Historically, energy costs associated with pumping the treated water through the membranes have limited widespread application for the treatment of high volumes of municipal wastewater. However, recent advancements and developments in membrane technology have led to reduced process energy costs and induced wider application for municipal wastewater treatment (Stephenson et al., 2000). This report describes a small and pilot scale demonstration study conducted to test a woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) process for use in domestic wastewater treatment. The study was conducted at Durban Metro Southern Wastewater Treatment Works, Veolia Plant, South Africa. The main objective of this project was to develop and evaluate the performance of an aerobic woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) for small scale domestic wastewater treatment. The experiments were oriented towards three sub objectives: to develop the membrane pack for immersed membrane bioreactor based on WF microfilters; to evaluate the hydrodynamics of WF membrane pack for bioreactor applications; and to evaluate the long-term performance and stability of WFM-IMBR in domestic waste water treatment. The literature was reviewed on membrane pack design for established commercial IMBR. The data collected from literature was then screened and used to design the WF membrane pack. Critical flux was used as the instrument to measure the WF membrane pack hydrodynamics. Long-term operation of the WFM-IMBR was in two folds: evaluating the performance and long term stability of WFM-IMBR. The membrane pack of 20 flat sheet rectangular modules (0.56 m by 0.355 m) was developed with the gap of 5 mm between the modules. The effects of parameters such as mixed liquor suspended solids or aeration on critical flux were examined. It was observed that the critical flux decreased with the increase of sludge concentration and it could be enhanced by improving the aeration intensity as expected and in agreement with the literature. Hence the operating point for long term subcritical operation was selected to be at a critical flux of 30 LMH and 7.5 L/min/module of aeration. Prior to the long term subcritical flux of WFM-IMBR, the operating point was chosen based on the hydrodynamic study of the WF membrane pack. The pilot scale WFM-IMBR demonstrated over a period of 30 days that it can operate for a prolonged period without a need for cleaning. Under subcritical operation, it was observed that there was no rise in TMP over the entire period of experimentation. Theoretically this was expected but it was never investigated before. Good permeate quality was achieved with 95% COD removal and 100% MLSS removal. The permeate turbidity was found to be less than 1 NTU and it decreased with an increase in time and eventually stabilized over a prolonged time. Woven fibre membranes have demonstrated great potential in wastewater treatment resulting in excellent COD and MLSS removal; low permeate turbidity and long term stability operation. From the literature surveyed, this is the first study which investigated the use of WF membranes in IMBRs. The study found that the small scale WFM-IMBR unit can be employed in fifty equivalence person and generate effluent that is free of suspended solids, having high levels of solid rejection and has acceptable discharge COD for recycle. Future work should be conducted on energy reduction strategies that can be implemented in WFM-IMBR for wastewater treatment since high energy requirements have been reported by commercial IMBRs.