The overall process of water treatment is a compilation of various unit processes including: aeration, disinfection, the mixing of chemicals, flocculation, sedimentation, and filtration. The arrangement of these various unit processes into different treatment configurations provided the basis for laboratory-scale experimentation in which the zeta potential, turbidity, alkalinity, and pH were monitored to determine the optimum operating mode for the Carvins Cove water treatment plant in Virginia during June and July, 1979. Results indicated that none of the treatment configurations tested produced significantly different results. Marginal improvement in turbidity removal was accomplished when alum was added after aeration rather than before aeration. The use of aeration did not significantly affect the coagulation process. Rapid mixing of the alum with a jar test apparatus did not significantly affect the turbidity removal achieved. The cationic polymer, CatFloc T, did not reduce the low turbidity of the raw water. / Master of Science

The influence of alum concentration, pH and the molecular weight of organic substances present in a water were evaluated in regards to the removal of trihalomethane (THM) precursors from a surface water supply, Peak Creek, in southwestern Virginia. Water was coagulated with various doses of alum with the pH uncontrolled and with the pH controlled at 5.2 - 5.3. Raw water and treated waters selected for efficient turbidity and optimum total organic carbon (TOC) removals were concentrated 400X using vacuum evaporation at a temperature of 40° C. Concentrated waters were fractionated in regards to molecular weight (MW) with columns packed with Sephadex G-25 and G-75 gels. The fractionated samples were chlorinated for 96 hours and THM production was determined. A preliminary investigation explored the effect of coagulant alum concentration in regards to removal turbidity, TOC and THM precursors from VPI Duck Pond water. A second preliminary investigation involved determining the MW chromatographs of raw and treated Claytor Lake and Peak Creek waters concentrated to different degrees. The results indicated that THM precursors and heavier MW organic substances were preferentially removed from water by alum coagulation; that conducting alum coagulation at pH 5.2 - 5.3 induced more effective turbidity, TOC and THM precursor removals; and that TOC concentration was a more effective surrogate parameter than turbidity for determining the removal of THM precursors. / Master of Science

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

A pilot plant study was conducted in Newport News, Virginia to investigate the effectiveness of powdered activated carbon [PAC] and granular activated carbon [GAC], with and without preoxidation, for reducing trihalomethane [THM] precursor concentrations in Harwood's Mill Reservoir water. Preoxidation with ozone followed by GAC is referred to as the "biological activated carbon" [BAC] process. This study showed that the GAC and BAC processes obtained the same level of organic removal; however, BAC would provide longer bed life and require less carbon than the GAC process. PAC treatment of alum coagulated water provided significantly higher TOC and THMFP removals than alum coagulation alone. The use of a preoxidant (ozone) with PAC slightly improved the organic removal efficiency. While treatment by PAC increased THMFP removals, it was not as efficient as the GAC and BAC processes. UV absorbance measured at 254 nm and TOC were found to be good surrogates for THMFP in the GAC column, but not in the BAC column. / Master of Science

This study was conducted to examine the kinetics of manganese sorption on oxide-coated filter media. Initial experimentation confirmed the findings of other investigators, the Mn²⁺ sorption capacity of oxide-coated media increases as solution pH increases. Further study revealed that uptake rate kinetics could be described by first order kinetics and also increased with increasing solution pH. The addition of free chlorine (HOCl) to solution greatly enhanced Mn²⁺ uptake rate kinetics. Later studies indicated that the oxide coating had very little impact on the physical properties of the media tested. Actual data from a water treatment plant filter confirmed laboratory experimental results by showing that sorption of soluble manganese does indeed occur on oxide-coated filters. The water treatment plant data also suggested that the sorption kinetics were relatively rapid, again upholding laboratory findings. Results from the manganese kinetics and sorption experiments were combined to formulate a theoretical model which would predict manganese breakthrough in a filter, given a known set of loading parameters. Preliminary use of the model indicated that oxide-coated filters could sorb significant quantities of soluble manganese before detectible levels of manganese appear in the effluent. / Master of Science

Human enteric viruses are present at low levels in sources of potable water. Due to the low minimum infective dose required for such viruses, these low levels are of public health significance and will become more important as water reuse increases. The effectiveness of alum coagulation for virus removal was evaluated using a synthetic water seeded with monodispersed poliovirus LScl. Experiments were done using 10(3),10(4),10(6) Plaque Forming Units (PFU) per liter. A microporous filter concentration technique was used post treatment to increase the virus titer to make possible virus enumeration by plaque assay on BGM cell cultures. Preliminary work was done to determine the efficiency of the concentration technique at 10(3),10(4),10(6)and PFU per liter. An average of 30.9 per cent of the original PFU were recovered. Two coagulation test methods were used at the lower virus titers. In one, virus was added to the system after the coagulant during the flash mix period and in the other, the coagulant was added to water already seeded with virus. Removals were similar for both conditions. Alum coagulation was found to remove 95 percent of the virus present at the low titers. This efficiency of virus removal is similar to that observed at high initial virus titers. Therefore, it appears that alum coagulation is an effective virus removal method. / Master of Science

In anticipation of government mandates regulating the quantity of the toxic mutagen, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone, which can be released into potable waters or from industrial facilities, technologies for monitoring the concentration, reducing the quantity, and inhibiting the formation of this compound were investigated. Adsorption of the chlorinated hydroxyfuranone from laboratory systems (pH 7.2, 22°) utilizing the non-polar, polymeric resin, Amberlite XAD-4, was successful. As these system conditions are comparable to those present in drinking water treatment facilities, application of this resin to such systems should be investigated. However, typical concentrations of the chlorinated mutagen released from such facilities are some 100 times less then those employed in laboratory experiments. As such, highly sensitive analytical technology, such as fluorescent spectroscopy, would be required for direct detection of the mutagen in these aqueous systems. Since development of a fluorescent adduct of the mutagen, through either Schiff's base or halogen replacement reactions, failed, application of the adsorption methodology was not investigated. Approaching the problem in a different manner lead to ° investigations aimed at reducing the formation of the mutagenic compound. Since the mutagen is formed upon chlorination of waters containing lignin derived materials, lignification in intact growing plants, and the effects of modified substrates on this process, were investigated. All modified substrates tested increased the uptake of a C¹⁴ labelled lignin precursor into the lignin containing fraction of a living poplar stem. Research continues in this area to determine through what mechanism these compounds are affecting lignification. / Master of Science / incomplete_metadata

Manganese is typically found in all water supplies in the United States. Manganese concentrations are usually higher in water obtained from groundwater sources or resei:voir hypolinutlons. This is because manganese is more soluble in the reducing conditions normally found in these waters. Although manganese is not known to cause any health related problems, the secondary drinking water MCL for manganese is 0.05 mg/L. This standard was set to eliminate aesthetic problems associated with manganese bearing waters. In this study continuous-flow filters were operated in both pre-oxidative (oxidized Mn applied to filters) and auto-oxidative (soluble Mn applied) modes. The oxidants used were dllorine (HOCl/OCl⁻) , potassium permanganate (KMnO₄), chlorine dioxide (ClO₂), and ozone (O₃). Other experimental parameters included: filter media type - manganese coated or non-coated, filter loading rate --2 to 5 gpm/f², operating pH -- pH 6 to pH 9, and temperature --5 to 25℃. The most important experimental parameter was whether or not the filter media had a prior oxidized coating of manganese. If this was the case the filter produced an effluent concentration of manganese below the MCL under all pre-oxidative conditions and under auto-oxidative conditions when the pH was above neutral. Increased flow rate through the filter caused deeper penetration of manganese into the filter bed. This should not prove to cause an effluent breakthrough problem for filter depths typically used in water treatment plants. Temperature and pH effected the reaction rate of manganese oxidation in both the pre- and auto-oxidative modes. In most cases th.is did not effect the effluent quality from manganese coated filter media. However, when non-coated media was used and no oxidant was added, a decrease in pH or temperature usually adversely effected effluent quality. / M.S.

Little information is available regarding the applicability of various disinfectants to the control of microbial growths within water distribution systems, especially in relation to "nuisance" organisms. With regards to microbially mediated iron precipitation, an isolated heterotrophic iron precipitating bacterium was identified. An investigation of free chlorine, chloramines, and chlorine dioxide was undertaken to examine their applicability in the control and/or elimination of this type of deterioration in water quality. Environmental conditions were then varied to determine their effects on the disinfectant's efficiencies. The isolated bacterium was identified as Pseudomonas cepacia. It was determined that chlorine dioxide offered a serious challenge to chlorine as a secondary disinfectant on the basis of its biocidal capabilities and stability. Solution pH affected free chlorine's efficiency the greatest, while chloramine's poor efficiency suggested that its use should be avoided in areas of microbial iron precipitation. Water temperature and turbidity showed a minimal effect on the rate of inactivation of P. cepacia for all the disinfectants under consideration. / Master of Science

M.S.