The overall aim of this research was to contribute to the optimisation of aerobic wastewater treatment processes in sequencing batch reactors, by investigating the performance of the process with real and model wastewaters in order to achieve the highest possible reduction of influent COD with the minimum reactor volume and oxygen consumption. Six industrial wastewaters from the food and drink companies were treated in lab-scale aerobic sequencing batch reactors (SBRs) inoculated with soil and monitored for COD and total suspended solids (TSS) removal. The results showed high COD removal efficiencies for all the wastewaters, in the range of 64-95 %. Extended aeration tests were carried out on the reactor effluents and the results indicated that the residual soluble COD was not further biodegradable. This indicates that the soluble BOD removal in the reactors was virtually 100 %. The biodegradation efficiency was investigated over two values of the solids retention time (SRT) and the performance of the reactors was essentially unaffected by the SRT (in the range of 7-18 days considered in this study). This means that very good COD removal can be achieved at relatively lower SRT, with potential savings in capital and operating costs. The removal of TSS for the wastewaters was not satisfactory, largely due to the low food to microorganism (F/M) ratios (0.13-0.29 kg COD/kg biomass.day) in the reactors. Three batch tests at different initial substrate to biomass (So/Xo) ratios were carried out on each of the two industrial wastewaters for kinetic characterisation of the wastewaters. Oxygen uptake rate (OUR) was measured during the tests and the OUR profiles were used for the estimation of the kinetic parameters using a mathematical model consisting of substrate hydrolysis, biomass growth and endogenous metabolism. The results showed large variations with regards to the values of the parameters for each wastewater due to day-to-day variability in the biomass's response to substrate utilisation. For the two industrial wastewaters, the hydrolysis rate constant (kh) and half saturation constant for slowly biodegradable substrate (KX) were found to be in the range of 2.21-14.8 kg COD/kg biomass.day and 0.006-0.45 kg COD/kg biomass respectively. The maximum growth rate (μmax) and the half saturation rate constant for readily biodegradable substrates (KS) ranged between 1.21-7.3 day-1 and 0.004-0.89 kg COD/m3 respectively. The biomass growth yield (YX/S) and the endogenous metabolism coefficient (b) were found to be 0.3-0.57 kg biomass/kg COD and 0.001-0.41 day -1 respectively. The hydraulic retention time (HRT) and SRT were optimised in order to minimise the SBR volume and maximise the organic loading rate (OLR) of the SBR process. Two model wastewaters, glucose and ethanol, were used in the study. An experiment of eleven different SBR runs (HRT in the range of 0.25-4 days and SRT of 1-65.3 days) was carried on the glucose wastewater. Nine different SBR runs were carried out on ethanol wastewater (HRT in the range of 0.5-4 days and SRT of 1-73.6 days). The minimum HRT and SRT values for the successful operation for glucose wastewater treatment were 0.25 days and 3.1 days respectively while the minimum HRT and SRT for ethanol were 0.5 days and 4.9 days respectively. The highest corresponding OLR values from the minimum HRT and SRT which gave satisfactory process performance were 4.28 g COD/l.day and 4.14 g COD/l.day for glucose and ethanol wastewaters respectively, which are among the highest OLRs reported in the literature for aerobic conventional dispersed-growth processes. The calculated oxygen consumption and biomass production were found to depend on the SRT as well as the OLR, where in general, oxygen consumption increased while biomass production decreased at higher OLR. Batch tests were also carried out on the two model wastewaters for kinetic characterisation. The kinetic parameters for glucose wastewater were: 1.07-4.79 day -1 for μmax, 0.24-0.45 kg COD/m3 for KS, 0.04-0.1 day-1 and 0.47-0.6 kg biomass/kg COD for b and YX/S respectively. For ethanol wastewater, the kinetic parameters were: 0.99-2.3 day -1 for μmax, 0.001-0.04 kg COD/m3 for KS, 0.05-0.2 day-1 and 0.38-0.51 kg biomass/kg COD for b and YX/S respectively. A new mathematical model and procedure to calculate the periodic steady state of the SBR using a kinetic model of the biological process and values of the kinetic parameters was developed. This new procedure allows the direct calculation of the steady state profiles of biomass and substrate in the SBR without calculating the dynamics of the system from start up to steady state. The numerical accuracy of the procedure was discussed and the model was applied to show the effect of the operating parameters (SRT, HRT, length of the phases and number of cycles) on the steady state performance in terms of biomass and substrate concentrations. It was also shown how the model can be used for various applications like: optimisation of operating parameters for a minimum reactor volume; simulation of the competition between filamentous and floc-forming bacteria for bulking control; and calculation of the minimum volumetric mass-transfer coefficient required to maintain a desired oxygen concentration. In the end, the periodic steady state of the SBR was simulated for the industrial and model wastewaters at various values of the operating conditions (e.g. HRT, SRT, number of cycles) using the developed SBR model with values of kinetic parameters obtained from the various batch tests. The predicted model performance in terms of effluent quality and biomass concentration was compared with experimental results achieved during the treatment of the wastewaters. The simulation gave very good prediction of the extent of substrate removal for all the wastewaters. However, the prediction was not very accurate for biomass concentration. The study indicated that a good model prediction in terms of biomass production is strongly dependent on the values of the kinetic parameters especially b and YX/S.

This study was undertaken to examine the feasibilty of a low-cost aerobic system to treat greywater for reuse.Its purpose was to provide a system that would be easy to maintain, flexible and be affordable for households and small communities in developing countries. This thesis outlines and evaluates the key biological and chemical hazards associated with greywater reuse. It discusses the performance of a variety of wastewater treatment options in use. It presents details of the components of the greywater system,namely, an aerobic grease trap and slow sand filter. Reference is made to the evaporation and treatment bed and ultraviolet disinfection components, but these are not examined. The incorporation of vermitechnology in the preliminary stages of the system for reduction of organics in greywater is reviewed. This study takes the traditional approach to water quality assessment with the measurement of physical, chemical and biological indicators. Assessment of the system involved examining the input characteristics of the greywater, monitoring the vermiculture system and sampling the liquid discharge from the aerobic grease trap and slow sand filter for analysis of the quality indicators. The results obtained under the framework of this study have provided recommendations for further use of the aerobic grease trap and slow sand filter, while propsing an approach for an appropriate long-term monitoring program. / Master of Engineering (Hons)

The design or improvement of a biological wastewater treatment system requires the characterization of influent wastewaters, the characterization of the microbial community in the system, and a knowledge of the rates of biological reactions. The wastewater treatment system of the city of Ste-Julie (Quebec) consists of four facultative aerated lagoons operating in series. Batch reactor experiments were performed with the municipal wastewater of Ste-Julie to simulate the biological processes occurring in the lagoon system. The first, second, and third lagoons were characterized in terms of soluble BOD, soluble COD, total solids, total suspended solids, volatile suspended solids, and TOC. The influent wastewater is classified as weak wastewater containing a relatively low concentration of soluble BOD compared to total BOD. The microbial communities in the first three lagoons were characterized using the BIOLOG redox technology which allows the simultaneous testing of the populations for the utilization of 95 carbon substrates. Finally, the specific initial BOD or TOC removal rates were determined for the first three lagoons. (Abstract shortened by UMI.)

Thesis (M.Eng.) -- University of Western Sydney, 2004. / A thesis submitted in fulfilment of the requirements for the degree of Master of Engineering at the University of Western Sydney. Includes bibliography.

Thesis submitted in fulfilment of Master's Degree in Technology: Biotechnology, Durban Institute of Technology, 2004. / M

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

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