FY 1992 ABSTRACTS

• Transport and Fate of Microbial Contaminants and Suspended Sediments in the Great Bay: Effects on Water Quality and Management Implications
• Innovative Point-of- Entry (POE) Treatment for Petroleum Contaminated Water Supply Wells
• Evaluation and Automation of Small Pressure Filter Systems

FY 1992 Water Problems and Issues

The summer of 1991 began dry and got drier. Most streams in the state were at or below 7Q10 levels. Aquifers and water supply wells were also significantly taxed. The net results were limitations on water use in some urban areas, curtailment of some treated wastewater discharges due to the low stream assimilative capacities and communities renewing searches for new water supplies. Fortunately, this dry period ended at summer's end with Hurricane Bob. Unfortunately, Bob generated flooding problems. This see-saw season served to underscore the critical problems which New Hampshire has been facing for a number of years: the relationship between water supply and water demand; the effects of water contamination; and securing water supplies for the future. Although the State and Federal governments have continued to invest in data collection efforts, the past few years have seen successive decreases in gathering water quantity and quality data. Natural process variability continues to be an important foundation to understanding the State's water resources manifest.

TRANSPORT AND FATE OF MICROBIAL CONTAMINANTS AND SUSPENDED SEDIMENTS IN THE GREAT BAY: EFFECTS ON WATER QUALITY AND MANAGEMENT IMPLICATIONS
Principal Investigators: Dr. Stephen H. Jones, Mr. Richard Langan, Dr. Frederick T. Short, Dr. Larry G. Ward, University of New Hampshire
Descriptors: Water quality management; bacteria; suspended sediments; shellfish; eelgrass beds; contaminant transport; estuarine modeling; pollutants.

Problem and Research Objectives:
The purpose of this study was to assess how reduction of microbial contaminants occurs in Great Bay. The proposed research was designed to identify natural mechanisms within Great Bay that could be exploited to actively remove microbial contaminants from the estuarine water by eelgrass and oyster beds. Such information would be extremely useful for regulators/managers to better understand the fate of microbial contaminants and suspended solids in estuaries. An understanding of the m mechanisms functioning in the estuary that reduce pollutant levels in the water can be exploited by implementing these mechanisms in critical areas as best management practices to better eliminate pollution problems. Determination of the magnitude of microbial contaminant removal by shellfish and eelgrass beds allows for evaluation of the relative appropriateness of exploiting these two habitats to purify water within the estuary. Obviously, the practical value of demonstrating removal of indicator bacteria is that pathogens will probably also be removed, thus mitigating the potential threat to public health of people that consume shellfish or that are exposed to estuarine water. Success in these activities would potentially lead to opening previously closed shellfish grounds and expanding other recreational uses of the estuary. The research should also give valuable information on the relationship between suspended microorganisms and sediments in estuaries. The research makes a substantial contribution to the scientific literature regarding the role of these biological features as filters of estuarine water in tidally-dominated estuaries.

Principal Findings and Significance:
The routine surveys of water quality showed microbial contaminant concentrations to be temporally and spatially variable. As previously observed, levels of indicators were strongly seasonal. During the initial period of the project in the summer of 1991, concentrations of microbial indicators were typically present at Furber Strait and Mid Bay at very low concentrations, often <10, and sometimes <1, enterococci, fecal coliforms and Escherichia coli per 100 ml. At Chapman's Landing, levels were higher than at Furber Strait and Mid Bay, but they were still lower than observed for other times of year. Levels at all 3 sites increased in October and remained high, relative to summer samples, through early January, and then again in the spring of 1992. Levels began to decrease again in late spring/early summer of 1992.

The stage of the tide was also a significant influence on microbial levels. At Furber Strait, levels of indicators were typically higher at high tide than at low tide, while the opposite was true at Chapman's Landing. The trend at Furber Strait is consistent with previous findings at Furber Strait over the previous three years, and confirms the observation that water leaving Great Bay at Furber Strait typically has lower levels of microbial contaminants than water entering the Bay at high tide. The trend at Chapman's Landing is expected, as the water at low tide should reflect the greatest influence of contaminated freshwater. The only significant deviations from the concentrations of fecal-borne microorganisms being higher at low tide occurred during the days following Hurricane Bob, in which case levels were much higher than normal at both tides.

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INNOVATIVE POINT-OF-ENTRY (POE) TREATMENT FOR PETROLEUM CONTAMINATED WATER SUPPLY WELLS
Principal Investigators: Dr. James P. Malley, Jr., Ronald Locandro and Jennifer Wagler, University of New Hampshire
Descriptors: Gasoline; groundwater contamination; treatment; advanced oxidation processes; UV/Peroxide; adsorption; synthetic resins; activated carbon.

Problem and Research Objectives:
An ongoing study by New Hampshire Department of Environmental Services (NHDES) has been looking at aeration and/or aeration plus granular activated carbon (GAC) as short term POE technologies to be used at contaminated sites. These technologies are considered the standard POE options for underground petroleum storage tank (UST) remediation. However, several problems exist with conventional POE technologies: (1) the combination of aeration plus GAC cannot cost-effectively meet the NHDES standard of 100 mg/L for methyl-t-butyl ether (MTBE); (2) MTBE is poorly removed by aeration and will rapidly exhaust the adsorption capacity of the GAC; (3) the fate of lead in petroleum contaminated ground waters and conventional POE units has not been examined; and (4) non-volatile dissolved organic carbon (NVDOC), which is abundant in petroleum contaminated ground waters, can interfere with conventional POE processes. While the impact of competitive adsorption has been examined for GAC in many surface waters, the impact of NVDOC from petroleum contamination on aeration and GAC has not received extensive study. For these reasons, the research project had three objectives:

Principal Findings and Significance:
Principal findings of the research are as follows:
UV/peroxide oxidation was extremely effective at removing MTBE from petroleum contaminated ground waters. Studies in simulated ground waters showed that greater than 90% removal of MTBE could be obtained in twenty minutes using a 15:1 (peroxide: MTBE) molar ratio (5.8 mg/L peroxide per 1000 mL MTBE). Initial MTBE concentrations up to 10,000 mg/L could easily be treated to meet the NHDES guidelines of 100 mg/L.

Ambersorb Tm (563, 572, 575) resins (Rohm & Haas, Philadelphia, PA) produced by pyrolysis of highly sulfonated styrene-divinylbenzene macroeticular ion exchange resins are a promising alternative to GAC for MTBE adsorption. In simulated ground waters Ambersorb resins had faster adsorption kinetics and about the same capacity as GAC. However, in actual contaminated ground waters AmbersorbTm resins maintained a high capacity for MTBE whereas GAC showed significantly lower capacities.

Sampling of petroleum contaminated water supplies during two seasons found no detectable (less than 0.01 mg/L) lead concentrations in the contaminated ground waters. These data are consistent with transport and fate models which suggest lead compounds will be attenuated (sorbed) by the soil.

Non-volatile dissolved organic carbon (NVDOC) did not significantly reduce the efficiency of aeration systems for removing BTEX 1, 2 DCA and MTBE compounds. Further, NVDOC did not affect GAC adsorption of BTEX or 1, 2 DCA compounds. Removal of MTBE by GAC adsorption was affected by BTEX compounds and studies are ongoing to determine if NVDOC affects MTBE adsorption on GAC.

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EVALUATION AND AUTOMATION OF SMALL PRESSURE FILTER SYSTEMS
Principal Investigators: Dr. Thomas P. Ballestero, Dr. M. Robin Collins, University of New Hampshire
Descriptors: Pressure filter automation; infiltration; water quality control.

Problem and Research Objectives:
Passage of amendments to the Safe Drinking Water Act required the US Environmental Protection Agency to specify where filtration of surface water sources is mandatory. Disinfection was also required for public water systems using surface water supplies. This project designed, constructed and installed a field scale pressure filter system for the Town of Contoocook, NH. The system was then run for seven months to evaluate the success of this technology for surface water treatment.

Principal Findings and Significance:
Software: The software system accomplished all primary objectives. The hardware could use more expansion slots to allow telephone notification capability.

Precoat DE Size: The influent flow rate decreased over time as the headloss in the filter increased because the DE pilot plant was operated at constant gravity with no flow controller. The best hydraulic performance was obtained by the medium grade DE (Celite 503). The 503 grade had slow headloss development, but did not treat quite as much volume as the larger 545 grade DE. Visual inspection of the filter coat by the operator showed uneven filter coating with the 545 grade at all precoat doses.

Precoat DE Dose: The optimum precoat dose for both the 503 and the 545 DE grades, as determined by headloss development, was 0.15 lb/ft2. For all grades of DE tested, 0.15 lb/ft. was the optimum dose for maximum volume of water treated at a minimum terminal headloss.

Bodyfeed Dose and Size: After determining the optimum precoat grade and loading, i.e., Celite 503 at 0.15 lb/ft2 dose, various bodyfeed combinations of DE size and dosage were tried. All bodyfeed application rates resulted in faster headloss development than using precoat only. Influent flow rates decreased more rapidly for all bodyfeed application rates than for precoat only.