Research currently being conducted at Virginia Tech has produced a viable pesticide wastewater clean-up procedure using biologically based materials. The system consists of two steps. First, pesticide laden wastewater is mixed with a lignocellulosic sorbent such as peat moss in a demulsification and sorption step. Second, the wastewater filtered rinsate is then passed through a packed column containing the same sorbent in a column sorption and filtration step. Although the system yielded adequate results and performed the tasks commensurate with its design, the original batch demulsification and sorption phase of the process had several operational problems. Namely, the system was large and not very portable, the recirculation system was not very reliable, and the entire step one process was laborious and time consuming to execute. These problems and limitations prompted the redesign of the step one process into a new, more efficient system. The new system consists of a steel frame similar to the old system. However, the new frame is smaller, lighter, more portable, and one person can easily operate and maneuver the new system. In addition, the new system provides a safer work environment for the operator. The frame surrounds the barrel and liner like a cage so that if the hand winch or the cable fails when lifting the liner out of the barrel, the operator is protected. The recirculation system has been automated such that it 1s self priming, and turns off when all the rinsate contained between the inner liner and outer barrel has been pumped dry. The come-a-long has been replaced with a hand wench that makes loading and unloading of the inner liner easier. Finally, the same pump that is used to recirculate the rinsate is used to transfer the rinsate onto the column for the second sorption and filtration step. There is now no need for additional pumps. After the system was designed and developed, it was tested on two pesticides, atrazine and metolachlor, to determine if the new system yielded results comparable to the old system. The atrazine concentration in the rinsate was reduced from an initial 721 mg/kg (ppm) in step one to 2 mg/kg in the step two column sorption and filtration phase. This represents an atrazine reduction of 99.72% over the entire two step process. The metolachlor concentration in the rinsate was reduced from an initial 704 mg/kg in step one to 30 mg/kg in the step two column sorption and filtration phase. This represents a metolachlor reduction of 95.74% over the entire two step process. The percent reduction of pesticide from the rinsate in the new system is comparable to the 99% reductions obtained using the old system. / Master of Science

M.S.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Biological removal of sulphate from wastewater can be achieved by using a gas mixture consisting of 80% hydrogen and 20% carbon dioxide as energy and carbon sources. A novel reactor, including a venturi device for optimal hydrogen gas-liquid contact, and geotextile for immobilisation of the sulphate reducing bacterial community, was introduced. Efficient, relatively stable sulphate removal was obtained when the reactor was operated in continuous mode. The maximum sulphate removal rate obtained when the reactor was 8% packed with geotextile, was 1 g S04/(L.d) and 4 g S04/(L.d) when the reactor was 80% packed with geotextile. Kinetic batch studies showed that the highest sulphate removal rates were obtained at 29.5 °C; a pH of 7.5; initial sulphate concentration of 4000 mg/L; initial alkalinity of 1600 mg/L; cobalt concentration of 3 mg/L and when excess hydrogen gas was fed compared to what is stoichiometrically required (900 ml/min). Nickel addition showed inhibition at increased concentrations (>3 mg/L). The biofilm structure was observed on the geotextile with electron microscopy, while the viability of the biofilm was indicated with fluorescence microscopy. These observations indicated the suitability of the geotextile as a support material for biofilm formation in the sulphate reducing system. The stability of the sulphate reducing community was analysed, using the T-RFLP protocol. It was shown that the composition of the community changed after a period of 3 months, when the reactor was subjected to environmental changes. The reactor was also observed to be more efficient in terms of sulphate removal after the environmental changes, of which the temperature change from an average of 39 to 29.5 °C was the most prominent. Subsequently, it was speculated that the population shift was in favour of a more efficient system for sulphate removal. A dynamic, viable, mesophilic sulphate reducing community was therefore observed on the geotextile support, responsible for successful sulphate removal in a novel venturi-reactor. Defining optimal operating conditions, and a knowledge of biofilm structure and composition may contribute to the successful implementation of the biological sulphate removal component of the integrated chemical-biological process for the treatment of industrial wastewater, when hydrogen and carbon dioxide are supplied as the energy and carbon sources, respectively. / AFRIKAANSE OPSOMMING: Ongewenste industriële afval-water kan biologies behandel word deur 'n gasmengsel van 80% waterstof en 20% koolstofdioksied te gebruik vir sulfaat verwydering. 'n Reaktor wat 'n venturi apparaat bevat vir optimale waterstofgas-vloeistof kontak, asook geotekstiel vir die immobilisasie van die bakteriële sulfaatverwyderende gemeenskap, is bekend gestel. Effektiewe, relatief stabiele sulfaatverwydering is waargeneem sodra die reaktor op 'n kontinue basis gevoer is. Die optimale sulfaat verwyderingstempo wat bereik is as die reaktor 8% met geotekstiel gevul was, was 1 g S04/(L.d) en 4 g S04/(L.d) wanneer die reaktor 80% met geotekstiel gevul was. Kinetiese groepstudies het getoon dat die beste sulfaatverwydering bereik is by 'n gemiddelde temperatuur van 29.5 °C; pH van 7.5; aanvanklike sulfaatkonsentrasie van 4000 mg/L; aanvanklike sulfied konsentrasie van 268 mg/L; aanvanklike alkaliniteit van 1600 mg/L; kobalt konsentrasie van 3 mg/L, asook wanneer 'n oormaat waterstofgas gevoer is (900 ml/min), in vergelyking met wat stoichiometries benodig word. 'n Verhoogde byvoeging van nikkel by die voerwater (3 mg/L), het tekens van inhibisie getoon. Die biofilm struktuur is waargeneem op die geotekstiel met behulp van 'n elektronrnikroskoop, terwyl die lewensvatbaarheid van die biofilm aangedui is met behulp van fluoressensie mikroskopie. Hiermee is die bruikbaarheid van geotekstiel as 'n ondersteunings-matriks bevestig. Die stabiliteit van die sulfaatverwyderende gemeenskap is ondersoek deur die T-RFLP protokol te gebruik. Hiermee is aangedui dat die samestelling van die gemeenskap verander het na die 3 maande toets periode, toe die reaktor onderhewig was aan omgewings veranderinge. Die reaktor het ook 'n verbetering in sy sulfaatverwyderings vermoë getoon na hierdie tydperk van omgewingsveranderinge, waarvan 'n temperatuur verandering vanaf 'n gemiddeld van 39 na 29.5 °C die prominentste was. Dit is dus gespekuleer dat die populasie verskuiwing ten gunste was van 'n beter sisteem vir sulfaatverwydering. 'n Dinamiese, lewensvatbare, mesofiliese sulfaatreduserende gemeenskap, verantwoordelik vir die sulfaatverwydering in die venturi-reaktor, is dus waargeneem op die geotekstiel as 'n ondersteuningsmatriks. Met hierdie evaluasie kan die insig wat verkry is in die reaktor samestelling en die optimale kondisies vir die reaktor werking, bydra tot die suksesvolle implementasie van die biologiese komponent, in die geïntegreerde chemies-biologiese proses vir die behandeling van industriële afval water, wanneer 80% waterstof en 20% koolstofdioksied gas as energie en koolstofbron respektiewelik, gebruik word.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

The bacterial flora of groundwater obtained from wells and distribution sites was investigated from both an ecological and a public health perspective. A majority of the isolates were oxidase positive, non-fermentative, gramnegative bacilli. Extensive heterogeneity of groundwater microflora, as determined by biochemical characterization and antibiograms, was observed both within and among welldistribution (N-D) systems. Of the unique isolates (sorts) found in the W-D systems, 75% were resistant to 2 or more antibiotics at clinically significant concentrations. Community diversity within W-D systems was evaluated by rarefaction which failed to reveal a general trend. Standard plate counts in 2 of 3 wells were significantly higher on Standard Methods Agar diluted ten-fold than on the same medium at the standard concentration. Pseudomonas aeruginosa, Flavobacterium sp., Aeromonas hydrophila and Yersinia enterocolitica were detected in 21, 18, 7 and 3% respectively of water samples analyzed over a 12 month period. A selective medium was developed for the isolation of Flavobacterium sp. and was effective in suppressing 98% of the background flora when used in a membrane filtration (MF) procedure. Yersinia Selective Agar was employed in an MF procedure for the isolation of Y. enterocolitica. The use of anaerobic incubation in this procedure effectively suppressed background growth both in the presence and absence of an antimicrobic supplement. Anaerobic incubation of m-endo LES Agar (AN-MF) was effective in suppressing non-coliform growth in the total coliform MF test and markedly reduced the frequency of overgrown plates. The AN-MF appeared to obviate the need for selective chemical agents and thus has potential value in the isolation of stressed coliforms.

The aim of the investigation was to compare the performance of an anaerobic baffled reactor (ABR) with a completely mixed anaerobic reactor (CMAR). The ABR was operated with a hydraulic retention time (HRT) of 20 h while the CMAR was operated at 20 d. A control experiment was conducted with a CMAR operated at a constant hydraulic retention time and substrate feed concentration. During the first phase, the start-up performance of the ABR and CMAR were compared. In the second phase of the study the steady state COD removals were compared. The laboratory completely mixed anaerobic reactor was a 20L glass vessel with a stirrer coming in through the neck. A second type of reactor, anaerobic baffled reactor (ABR) was also operated. The ABR was a rectangular perspex box with internal vertical baffles alternately hanging and standing. The baffles divide the reactor into eight compartments with a total working volume of 7.5 L. Each baffle is angled at about 45Q to distribute the flow towards the centre of the upcomer. The reactors were seeded with raw sewage and allowed to stand for 3 days after which a continous feed of sucrose and basal salts was commenced. The initial HRT for the ABR and the CMAR were 60 h and 30 days respectively. When the reactors reached steady state (pH, gas production, gas composition and alkalinity), the HRT was reduced in a stepwise fashion (ABR 60 h to 35 h to 20 h and CMAR 35 d to 30 d to 20 d). At the final HRT the COD removals were similar (67 %). The ABR took 120 d to attain final steady state while the CMAR took 200 d. The organic loading tests were undertaken with a stepwise increase (doubling) in the influent substrate concentration. The feeding commenced at an organic loading rate (OLR) of 4.8 kg/m(3).d for the ABR. The flow rate (HRT) into both reactors and other parameters were kept constant (HRT of 20 h and 20 d for ABR and CMAR respectively). The substrate concentration was increased from 4 gCOD/L (4.8 kg/m(3).d) to 64 gCOD/L (76.8 kg/m(3).d) for the ABR. For the CMAR it was increased from 4 gCOD/L (0.25 kg/m(3).d) to 32 gCOD/L (2 kg/m(3).d). The method used was to increase the organic loading rate until the reactors failed. Since the two reactors had different operating HRTs, the tests began when both had the same COD removal rate of about 60 % COD reduction. The same parameters as in the start-up period were monitored for both reactors. The CMAR had a COD removal efficiency ca. 70 %, which did not fluctuate when OLR was increased. The ABR reached a maximum COD removal of 80 %. An increase in the OLR led to an initial decrease in the COD removal until the biomass recovered and the high COD (80 %) removal rates resumed. The ABR reached a maximum OLR of 76.8 kg/m(3).d whilst the CMAR reached a maximum OLR of 2.0 kg/m(3).d. The investigations showed that the ABR could be operated at higher organic loads than the CMAR and give the same organic removal rate. This verified the importance of increasing the SRT/HRT ratio in anaerobic reactors. The CMAR, however, proved to be stable to changes in the influent feed strength, as there was no immediate noticeable changes in the gas production. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / Horizontal subsurface flow constructed wetlands (HSSF CWs) are being considered in South Africa as an alternative waste water treatment technology which is low in capital costs and typically requires less operational infrastructure when compared to conventional treatment technologies. HSSF CWs may thus be a potential solution for solving the challenge of ensuring reliable access to clean water for rural communities whose municipalities may not be able to afford the construction of a waste water treatment plant as well as not being able to supply sufficient technical expertise for the operation thereof. Proper design of HSSF CWs requires a detailed investigation into the hydraulic behaviour as it has a direct effect on the treatment performance in these systems. In this study, three available hydraulic modelling methodologies for HSSF CWs were compared and these are the impulse, step change integral and step change derivative modelling methodologies. Hydraulic data were generated from planted and unplanted pilot scale HSSF CWs using residence time distribution (RTD) studies and the modelling results using each methodology were compared. It was found that each methodology was capable of suggesting a different hydraulic behaviour for the same system being studied and since it is not possible to evaluate an analytical answer to the problem independently it was not possible to determine which modelling methodology was the most accurate. Practical limitations of the experiments used to feed hydraulic data to the respective methodologies were also highlighted. Despite a well-designed sampling regime it was not possible to capture sufficient data surrounding the peak of the impulse response curve and may have impacted negatively on the modelling results. No such difficulties were encountered with the step change tracer experiments. The mathematical techniques which each methodology employs were also critically assessed. It was found that numerical differentiation in the step change derivative modelling approach introduced noise into the RTD curve and may have affected subsequent results. Ultimately each methodology has its own associated strengths and weaknesses and choice of methodology may be dictated by other factors such as cost to set up the hydraulic experiment as well as equipment availability. Tasks two and three of this dissertation dealt with how Biomimicry can be used as a tool to develop more sustainable HSSF CW designs and hydraulic modelling processes. In task two, hydraulic data generated from the first task were used to develop estimates of the velocity profiles inside a planted HSSF CW to identify regions most prone to clogging, a phenomenon which would be a serious concern for rural communities whose sole water treatment system would be the CW. Biomimetic design principles were combined with the modelling results to develop a modular system design allowing for sections of the CW to be removed for cleaning while still allowing for continuous treatment of the waste water. Task three explored the use of heat as a hydraulic tracer. Heat is considered more environmentally friendly when compared to chemicals as tracers as the CW can equilibrate to ambient conditions post study and the effluent does not require dedicated disposal infrastructure. Heat is non-conservative in these systems and processes such as absorption by the subsurface media and loss to the surroundings distort the hydraulic response curve from which the hydraulic behaviour cannot be directly obtained. In this study a mathematical model was developed which maps a heat tracer response curve to one which would be obtained if a conservative chemical tracer were used. It was tested by conducting a combined heat-chemical tracer study on an unplanted laboratory-scale HSSF CW and the predicted chemical response curve was compared with the actual experimental response curve. The model performed satisfactorily indicated by a 5% and 6% relative difference in the Peclet number (Pe) and mean of the RTD respectively. In each of these chapters, an abstract is provided which summarizes the main findings of the study. / MT2017

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2015. / In this study, comparative sorption studies of the major metal ions (Mg2+, Ca2+, K+ and Na+) in the brine wastewater were performed on hydrophilic materials (PAN nanofibre, PAN+TiO2 nanofibre, PAN+ZEOLITE nanofibre) and Purolite S950 resin to investigate their uptake performances. For this purpose, PAN nanofibre was electrospun and subsequently doped with 3 wt% each of titanium dioxide and zeolite respectively, in controlled experimental conditions in order to improve its performance. This was followed by the characterization of the respective hydrophilic materials (PAN, PAN+TiO2 and PAN+ZEOLITE nanofibres) using Fourier Transform Infrared Spectroscopy (FT-IR); Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). SEM showed that the incorporation of titanium dioxide or zeolite into the PAN structure made the surface rougher than that of the ordinary PAN nanofibre and FT-IR revealed the peaks belonging to titanium dioxide and zeolite respectively, showing the inorganic materials are within the PAN structure. The XRD analysis complemented the FT-IR of the nanofibres by revealing the peaks characteristic of titanium dioxide and zeolite are present on the PAN structure.

Treatment efficiency in a constructed wetland is related in part to the amount of time that a wastewater remains in the system. Current design methods idealize the system as a plug flow reactor and use a "residence time" based solely on the volume of the cell and the flow rate. Under this assumption, every element of wastewater entering the wetland cell experiences the same residence time. It is understood that this idealization ignores the existence of longitudinal dispersion, short circuiting and stagnant regions within the wetland cell. The result of these phenomena is a distribution of residence times. In other words, portions of the effluent exit the cell earlier than predicted, resulting in undertreatment, and portions exit late, resulting in excess treatment. The average concentration of treated wastewater at the outlet is a function of this distribution and the reaction kinetics associated with the waste. The overall effect of a distribution of residence times is reflected in a reduction of treatment efficiency at the outlet. Hydraulic regimes of constructed wetland systems were investigated at a pilot project site providing tertiary treatment of a pulp mill wastewater. Two vegetation types, bulrush and cattail, were investigated and compared to nonvegetated and rock-filter cells with identical configurations. Tracer studies used a fluorescent dye and were performed over the course of a year. Dye was input as a pulse at the inlet end of the cell and sampled over time at the outlet end to obtain concentration breakthrough curves. From these curves, time to peak, actual mean detention times, degree of dispersion, and extent of dead space were calculated, as well as predicted treatment efficiency. Results indicated varying degrees of dispersion, short circuiting, and dead space in the individual cells. Analysis of the residence time distributions provided estimates of the "active" volume of the treatment cell and the degree of short circuiting in the system. Effective volume of the planted cells ranged from 15 to 25% of full volume. Early arrivals of the peaks of the distributions, indicative of short circuiting, ranged from 30% to 80% of the theoretical detention times. A first order treatment model and a kinetic coefficient, k, were assumed, and corresponding treatment efficiencies were compared to the theoretical treatment of an ideal plug flow reactor. Reduced treatment efficiencies for the planted systems ranged from 2 to 20 %, by this estimation. Many references attempt to analyze wastewater treatment systems by refering to two models: dispersed plug flow and an approximation of tank-in-series. These models were investigated as potential descriptions of the hydraulic regime present in constructed wetlands. Residence time distributions of the constructed wetlands in this study indicated flow was not exclusively dispersed plug flow. This simplified model does not account for the exchange of material with "dead" space in the wetland cell. The data suggest a combination model of dispersed plug flow with a transient storage zone component may be more appropriate. / Graduation date: 1994

Co-produced water from the oil and gas industry represents a significant waste stream in the United States. Produced water is characterized by high levels of total dissolved solids (TDS), dissolved organics and oil and grease. Among the wide variety of organics present in the water, the concentration of hazardous substances such as benzene, toluene, ethylbenzene, and xylenes (BTEX) can reach 600 mg/L and the concentration of non-hazardous carboxylate can be as high as 10,000 mg/L (API, 2002). Regulations governing the disposal of produced water are tightening and the interest in reusing treated produced water is increasing in the United States particularly in regions with scarce water supplies. In order to reuse produced water, removal of both the inorganic dissolved solids and hazardous organics such as BTEX may be necessary. The main goal of this research was to investigate the feasibility of using a combined physicochemical/biological treatment system to remove the organic constituents present in saline produced water. In order to meet this objective, two separate biological treatment techniques were investigated: a vapor phase biofilter (VPB) to treat the regeneration off-gas from an upstream surfactant-modified zeolite (SMZ) adsorption system and a membrane bioreactor (MBR) to treat the carboxylate and BTEX constituents that penetrate an upstream SMZ system. Each of the biological pretreatment systems was investigated first in the laboratory treating synthetic produced water and then in the field coupled to an SMZ adsorption system treating produced water. Both of the biological treatment systems were capable of removing the BTEX constituents both in the laboratory and in the field over a range of operating conditions. For the VPB, separation of the BTEX constituents from the saline aqueous phase yielded high removal efficiencies. However, carboxylates remained in the aqueous phase and were not removed in the combined VPB/SMZ system. In contrast, the MBR was capable of directly treating the saline produced water and simultaneously removing the BTEX and carboxylate constituents. The major challenge of the MBR system was controlling membrane fouling, particularly when the system was treating produced water under field conditions.