M.Dip.Tech.(Environmental Health) / At the onset of this project the aim was to utilise fly ash, supplemented with lime, to stabilise sewage sludge, in so doing create an artificial soil. This would be an environmentally friendly method of disposing of both the fly ash 'and the sewage sludge which are both considered wastes. The sewage sludge was pasteurised by the temperature produced by the exothermic reaction between the moisture ofthe sewage sludge and the high pH ofthe fly ash and the lime. Initially very high concentrations of lime were utilised to achieve the pasteurisation of the sewage sludge. These levels proved to be adequate to completely sterilise the sludge, rather than pasteurise it, as temperatures in excess of 1000e were obtained and maintained for a prolonged period. The product, SLASH, should ideally maintain some of the non-pathogenic microorganisms to facilitate natural degradation processes in the soil. .It was thus decided to minimise the lime addition and maximise the ash usage without losing the necessary soil-like texture of the SLASH product and still insuring pasteurisation. Various 10kg tests were conducted on differing ratios of sewage sludge, ash and lime. The mixtures were contained in insulated 220 litre drums in order to ensure a minimum of interference from environmental factors. The tests were conducted with the drums sealed and unsealed, as well as with coarse and finely milled lime-stone. These laboratory scale tests led to the establishment of a preferred 6:3:1 ratio ofsewage sludge to ash to lime. After an international visit to a plant manufacturing a similar product, it was suggested that the ratio be amended to 6.3:3.4:0.6 of sewage sludge to ash to lime. Tests showed that although the temperatures obtained when using this ratio were insufficient for pasteurisation, pasteurisation did occur. This was attributed to the maintenance of the pH of the product above 12 for more than 24 hours. This severely stressed the microorgansims and they died. No pathogenic bacteria were detected in the analyses from these tests, but the total aerobic bacterial count indicated the presence of some microorganisms which would become part of the soils natural flora.

The principles behind anaerobic digestion are fairly well understood, but the limits of application of each digester design are not known. Because there are significant differences in the properties of the many wastewaters requiring treatment optimal anaerobic digester performance requires the matching of feed characteristics to a digester design and mode of operation. No consensus has yet emerged on digester design, operating conditions or feed/digester match-ups. In this study, three bench scale retained biomass anaerobic digester designs were examined for their response to a sequence of varied hydraulic retention times (HRTs) and influent wastewater concentrations. The digester designs studied were the upflow anaerobic filter, the upflow anaerobic expanded bed and the upflow anaerobic sludge bed. The wastewater was screened and diluted dairy cow manure obtained from the UBC dairy barn. The parameters monitored included the total and soluble chemical oxygen demand (TCOD and SCOD), volatile and suspended solids (VS and SS), total volatile fatty acids (VFAs), total Kjeldahl and ammonia nitrogen (TKN and NH₃-N), pH, biogas production, and the methane (CH₄) and carbon dioxide (C0₂) content of the biogas. Wastewater treatment efficiencies, measured in terms of TCOD, SCOD, VS, and TVFA removals, and methane productivity and methane yield for each of the digester designs were examined for the range of the operating conditions. The anaerobic filter digester effected a mean TCOD removal efficiency of 47% ± 14% at a mean 4.0 day HRT, 51% ± 9% at a mean 2.3 day HRT and 35% ± 11% at a mean 1.3 day HRT. The expanded bed digester effected a mean TCOD removal of 45% ± 15% at a mean 4.3 day HRT, 38% ± 12% at a mean 2.5 day HRT and 28% ± 9% at a mean 1.3 day HRT. The sludge bed digester effected a mean TCOD removal of 53% ± 9% at a mean 3.8 day HRT, 45% ± 12% at a mean 2.2 day HRT and 32% ± 10% at a mean 1.2 day HRT. For all three digesters, the difference in the treatment efficiency over the range of HRTs tested, from 5 to 1.25 days was not in proportion to the change in HRT. Methane productivity, measured against either the removal or addition of substrate in terms of TCOD, SCOD, VS and TVFA, demonstrated considerable variability. Methane production increased with both substrate addition and substrate removal. Methane yield increased with increasing HRT. The sludge bed digester generally exhibited the greatest but most variable methane yields. It produced 0.095 L CH₄/g VS added at a mean 3.8 day HRT and 0.037 L CH₄/g VS added at a mean 1.2 day HRT. The anaerobic filter delivered the greatest methane yield at the intermediate HRT, 0.044 L CH₄/g VS added at a mean 2.3 day HRT. The expanded bed demonstrated low methane yields over the range of feed strengths and HRTs tested. Biogas composition averaged 62.1% methane and 17.1% carbon dioxide for the anaerobic filter, 43.6% methane and 5.3% carbon dioxide for the expanded bed. and 61.1% methane and 18.9% carbon dioxide for the sludge bed. / Applied Science, Faculty of / Graduate

The extraction, separation and identification of volatile organic components of primary effluent before and after chlorination was undertaken to ascertain whether the chlorination of treatment plant effluents results in the formation of new volatile chlorinated organics. Extraction efficiencies of 70 to 90 percent of an aqueous solution of phenols were obtained by both continuous solvent extraction and sorption on a column of a macroreticular resin. Tests with primary effluent showed that the macroreticular resin recovered a slightly larger number of compounds than the solvent extractor which also suffered from emulsion problems.' Since the resin was also expedient in handling replicate samples it was adopted and further studies indicated that it had a capacity of 1.7 mg TOC/cc of resin and recoveries of the phenols were unaffected by pH or detergents. Preliminary separation of the. .components on the basis of acidity with .05'M^NaOH and diethyl ether and by thin layer chromatography on silica gel with pet ether and methanol proved to be useful. Gas chromatographic (GC) studies with various silicone liquid phases demonstrated that OV-101, 0V-17, and 0V-225 all provide good separation after optimization of temperature programs. Primary effluent samples taken from Lion's Gate Treatment Plant in North Vancouver on Monday mornings proved to be remarkably consistent in their GC 63 traces as monitored by Ni electron capture (EG) and flame ionization (FID) detectors. A series of spectacular new peaks was consistently observed by EC as a result of chlorination, but the FID showed only minor changes. Dosage levels of up to 120 mg/1 Cl₂ (NaOCl) produced similar chromatograms while a dosage of 200 mg/1 produced a new set of changes not found at the dosage levels used in treatment plants. Gas chromatographic studies with a micro- electrolytic conductivity detector showed that 10 or 11 new halogenated peaks in the neutral and basic fraction and 6 or 7 new halogenated peaks in the acidic fraction result from chlorination. These compounds all of which are in μg/l concentrations account for only 0.01 percent of the applied chlorine dosage but make up about 40 percent of the more volatile organically bound halogen present in chlorinated primary effluent. After a series of partially successful attempts by retention time, GC-MS and GC effluent trapping, a number of components were positively identified by a computerized GC-MS. TRirty-one compounds were positively identified by mass spectra and GC retention times, another 24 were tentatively identified by mass spectra and an additional seven were very tentatively identified by GC retention times. Only three of the compounds resulting from chlorination were positively identified. All compounds identified by mass spectra are present in concentrations in primary effluent. The implications of this study and suggestions for further investigations are also discussed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The adsorption of low concentrations of heavy metals, such as zinc, copper, lead and mercury, by various British Columbia coals was investigated. Five British Columbia coals were used as adsorbents for the four heavy metals described above. Batch tests were run on all five coals, namely, Hat Creek Oxidised, Hat Creek Unoxidised, Cominco Oxidised, Cominco Ash Waste and Cominco Production Coal. The optimum contact time for batch tests was found to be 60 mins. Batch tests provided a quick comparison of the adsorptive capacities of the five coals. Based on the batch tests data, the best performing coal from each of the Hat Creek and Cominco groups, namely, Hat Creek Oxidised and Cominco Ash Waste were chosen for further investigatory work using column tests. For the column tests, the influent concentrations were 2 mg/ℓ and less for zinc, copper and lead. Column work with mercury was carried out with influent concentrations of 5 μg/ℓ and less. Column tests showed the following:- a) Varying the cross-sectional area of the coal column from .001 ft² to .002 ft² has no significant influence on the adsorptive capacity. Both columns have diameters more than 10 times that of the average coal particle. b) The most crucial factor affecting adsorptive capacity is the pH of the influent. There is a definite decrease in capacity with decreasing pH. c) The capacity decreases with increasing flow rate, but the relationship is not linear. The decrease in capacity due to a flow rate increase from 1 to 3 Igpm/ft² is much greater than the decrease in capacity due to an increase from 3 to 5 Igpm/ft². d) Comparing the adsorptive affinities of zinc, copper and lead, it is seen that lead displayed the greatest affinity with copper second and zinc third. At 10% breakthrough concentration, the capacities displayed by Cominco Ash Waste coal for lead, copper and zinc were in the ratio of 12:6:1. The influent pH and initial concentrations involved were 4.0 and 2 mg/ℓ respectively, and the flow rate was 1 Igpm/ft². e) Using influents containing a mixture of zinc, copper and lead results in smaller individual capacities for Zn, Cu and Pb than would be achieved with single solute influents. But the total overall capacity of the coal for heavy metals is greater with mixed influents than with any single solute influent. f) Tests with mercury influents show that deterioration of the concentration of the mercury solution occurs at concentration of 5 μg/ℓ and less. g) Of the two coals chosen for column test work, Hat Creek Oxidised is the superior coal with regard to the adsorptive capacity of heavy metals. Tests run at an influent pH of 4.0 and influent concentrations of 2 mg/£ of each metal, showed the ratio of capacities of Hat Creek Oxidised: Darco activated carbon: Cominco Ash Waste for Zn to be 12.1 : 1.2 : 1.0, for Cu to be 11.9 : 1.7 : 1.0 and for Pb to be 3.8 : 0.7 : 1.0. An attempt was made to correlate the column effluent pH with the effluent metal concentration. It was found that this correlation is more pronounced at lower influent pH values. During the course of the column work, a growth of fungus was observed at the top of the coal columns. It is possible that adsorptive capacities were affected by this fungus. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The advent of high molecular weight polyelectrolytes has stimulated research into their use for BOD reduction in primary and secondary treatment and as sludge dewatering aids in vacuum filtration and centrifugation. Since many of these products have not been approved for use in domestic water supplies because of their possible toxicity to humans, it was felt that they may be toxic to the microorganisms in anaerobic digestion, activated sludge or other biological treatment processes. This research evaluates effects on the anaerobic digestion process. Three continuously mixed laboratory scale anaerobic digesters were operated at 32±1°C with a 30 day hydraulic and solids retention time. Digester number one served as a control and received sludge obtained by sedimentation of domestic sewage without the use of coagulants; number two received sludge obtained using 14 mg/l of a cationic Hercules Incorporated polymer, Hercofloc 814.2, as the coagulant; and number three received sludge obtained using 30 mg/l of ferric chloride as the primary coagulant and 1 mg/l of Hercofloc 836.2 as a coagulant aid. Waste stabilization calculations, based on influent and effluent BOD, COD, and VS results and on methane production, failed to indicate any toxicity or physical inability of anaerobic microorganisms to penetrate the floes formed as a result of the addition of coagulants as aids to sewage sedimentation. Calculations of waste stabilization from BOD₅, BODL , COD, and VS results indicated treatment efficiencies of approximately 81, 70, 62 and 59 percent, respectively, for all three digesters. Results of pH, alkalinity, and volatile acids testing of digester effluents and total gas production from the digesters did not indicate unbalanced treatment due to the presence of coagulants. pH and alkalinity results were, however, consistently higher in the digesters receiving chemically coagulated sludge than in the control digester, signifying a greater buffering capacity against digester upset. The effluent from digester number two was observed to settle more rapidly and leave a clearer supernatant than effluent from either of the other digesters. Subsequent Buchner funnel vacuum filtration tests produced values of specific resistance for effluents from digesters one and three that were 18 times greater than the values obtained for the number two effluent. Although the results were for the mixed digester contents rather than for the settled portion of the effluent, they indicate that little or no additional conditioning would be required prior to vacuum filtration dewatering of effluent from digester number two. A limited number of jar tests and settling column tests using a weak to medium strength domestic sewage, produced BOD₅ and COD removal efficiencies of 50 to 70 percent using 30 mg/l of FeCl₃ in combination with 0.5-1.0 mg/l of anionic Hercofloc 836.2. Similar efficiencies were achieved using 6-14 mg/l of either of the cationic Hercofloc polymers, 812 or 814.2, as the sole coagulant. An economic analysis was carried out comparing the total annual costs of primary and activated sludge treatment methods. Capital costs were amortized over a twenty-five year period at 10 percent per annum and were added to operation and maintenance costs to obtain total costs. The results of this analysis indicated that the maximum economic dosages of Hercofloc 814.2 added continuously to primary plants operating at capacity are 14.9, 10.2, and 6.6 mg/l for 1, 10, and 100 mgd plants, respectively. Similarly for ferric chloride and 0.5 mg/l of Hercofloc 836.2, the corresponding economic dosages of FeCl₃ are 51, 34, and 21.5 mg/l. These dosages are based on the assumption that an adequate degree of treatment can be obtained by chemical precipitation. Within the limitations of the economic analysis and based on jar test results, it was concluded that use of Hercofloc 814.2 as an aid to primary clarification of domestic sewage is not an economically attractive alternative to providing activated sludge treatment unless an adequate degree of treatment can be achieved at dosages somewhat less than 14 mg/l. On the other hand, use of ferric chloride and Hercofloc 836.2 was found to be economically attractive for plants in the 1-10 mgd range. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The evidence of heavy metal build up in the aquatic environment near sewage treatment plant outfalls around Vancouver,coupled with the generally held theory that secondary treatment is not required in this area, leads to the conclusion that a treatment method is required that is primarily aimed at heavy metal removal. In this study, jar tests were performed to evaluate the heavy metal removal efficiency of the lime-magnesium coagulation process. Five heavy metals (Cr³⁺ , Cu²⁺ , Pb²⁺ , Ni²⁺ and Zn²⁺ ) were all tested at initial concentrations of .5, 2.5 and 5.0 mg/1 individually and in combination. The experiments were performed on prechlorinated primary effluent and raw sewage at the natural alkalinity levels (120-130 mg/1 as CaCO₃), and some work was done at elevated alkalinity (190-200 mg/1). The need for filtration in the process was also researched. Results of the study indicated that the heavy metal removal efficiency was enhanced by the presence of Mg²⁺ at a given lime dosage for all of the heavy metals except nickel. A comparison indicated that intermediate lime treatment (220 mg/1) coupled with 33 mg/1 Mg²⁺ might be a more attractive process than just straight high lime treatment (400 mg/1). / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This research explored the effects of operational parameters on the prefermentation of primary wastewater sludge and the resultant wastewater characteristics changes at a full-scale in-line prefermenter, with due emphasis placed on the identification and resolving of practical problems. The settled sludge recycle flowrate was the main operational variable and the overall wastewater characterisation was based on the changes in the nutrients to carbonaceous material ratios across the prefermenter. The evaluation of prefermentation on wastewater nutrient ratio changes was performed under three different sludge operating conditions with regards to sludge elutriation rates, regulated at 0.7,2.2 and 3.7 kg sludge solids/m3 raw sewage. The corresponding sludge ages at these elutriation rates were calculated as 17.3, 2.5 and 7.5 days. At all three operating conditions the TKN/COD ratio increased (64, 46 and 20% respectively), with an average ratio of 0.057 mg N/mg COD in the raw sewage increasing to 0.082 mg N/mg COD in the settled sewage. These ratio changes limit the use and performance of certain biological nutrient removal process configurations. Linear relationships were identified for constituent removal levels across the prefermenter. Associations were based on solids removal (settleable solids vs. suspended solids), COD to solids removal (COD vs. suspended solids), nutrient to COD removal (TKN and TP vs. COD) and ammonia nitrogen change (ammonia vs. TKN) across the prefermenter. Solids (settleable solids and suspended solids) and COD removals against the prefermenter solids surface loading rates were also correlated. Although the operational conditions varied over the experimental stages, the scatter of data points still formed in most cases distinct linear trends that were quantified with linear equations. This study has also highlighted the importance to counterbalance the requirements of fermentation with the requirements of solids thickening and solids removal at in-line prefermenters. The sludge management function at prefermenters is crucial in cases where the downstream waste sludge handling capacity is limited, usually due to the absence of additional sludge thickeners. In the full¬scale prefermenter the minimum suspended solids removal (33%) was achieved at the lowest settled sludge solids content (4.25%), at a corresponding maximum volatile fatty acid process generation rate (5.7 mg VFA/l/h). These opposing results demonstrated the need to find a proper balance between the various operational fermentation and solids handling requirements. The solid and volatile fatty acid concentration profile down the prefermenter tank depth was determined at a high sludge blanket condition to demonstrate that the constituent mass inventory is about constant throughout the water and sludge layers respectively. The use of on-line sludge level detection instrumentation proved to be very beneficial to monitor sludge blanket height variations. The on-line data availability of the prefermenter sludge content simplified sludge age determinations. The increased solids loading on the prefermenter due to the internal sludge recycle places a limit on the level of thickening and solids removal that can be achieved in an in-line prefermenter. This aspect is not considered in detail in the available literature. Preliminary calculations at the case study site indicate that at the typical raw sewage suspended solids concentration (425 mg/l suspended solids), a solids loading of about 83 kg solids/m2 tank surface/d is created due to a sludge recycle rate of 0.05 m3 sludge/m3 raw sewage. This is related to an elutriation rate of 2.9 kg sludge solids/m3 raw sewage and a 5.6% total solids recycled sludge concentration, resulting in an APT feed concentration of 3158 mg/l solids. It is assumed that the recycled solids consist completely of resettleable solids. Unpredictable solids carry-over at peak flow conditions indicated however that loss of solids settleability and resuspension of solids do occur. Inhibitory substances can reduce the VF A generation performance of a prefermenter due to consumptive VF A counter-reactions. Escalating levels of sulphate in the raw sewage at the prefermenter was identified as a possible contributing factor for the reduction in the VF A content of the settled sewage over the experimental period. The surface scum collection system, transferring scum gravitationally with settled sewage from the fixed scum trough to the waste sludge sump, can dilute and lower the thickened waste sludge concentration unnecessarily. This problem was resolved by returning most of the scum transfer medium (settled sewage) with a submersible pump to the inlet of the prefermenter. The impact of wastewater prefermentation cannot be evaluated in isolation, based on the local prefermenter VF A production rate alone. The nutrient ratios and solids removal changes in the settled sewage from a prefermenter must be considered when evaluating the downstream biological nutrient removal process. The type of the prefermenter configuration employed is considered to be the determining factor to ensure sufficient operational flexibility is available at the primary treatment section of a water care works. / Dissertation (M Eng (Chemical Engineering))--University of Pretoria, 2007. / Chemical Engineering / unrestricted

In compacted Na-montmorillonite membranes, the pore-size, and surface charge will influence filtration processes of solutes. A dead-end hyperfiltration setup was utilized to: (a) study the intrinsic retention, membrane filtration coefficient, and solution flux of different membrane configurations and (b) model nitrate break-through effluent concentrations through the membrane. Scanning electron microscopy and solute analytical techniques were employed to assess what critical components of micro-pore parametrics would prevail in a non-bio stimulated remediation of simulated agricultural wastewater. Although high content bentonite membrane configurations (5 g clay at 2500 psi) offered better solute rejections with a 30 percent increase in the cell concentration, the compaction of the membrane had the most deterministic influence on the solution flux. The results reveal hyperfiltration of nitrate ions is a function of the compaction pressure and composition of bentonite in the mixed soils. High content bentonite membranes compacted at the optimal pressures offer promising solutions to nitrate contaminant remediation.

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