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Abstract:
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The use of overland flow is currently being studied as a way to treat
textile wastewater more cost-effectively " The response of this system to
treating textile waste during cold weather and modified operating times is not
fully understood. It is also not known whether treated effluent is amenable to
polishing by sand filtration, or if operation of the system poses a ground water
contamination problem.
By measuring the performance of the system while operating in cold weather
conditions and by modifying the application rate, ways of optimizing the system
can be determined. By assessing the response. of the treated effluent to sand
filtration, the potential for post-treatment by this method can be indicated.
By evaluating the results of soil and soil moisture tests, the potential for
ground water contamination can be assessed. Therefore, the objectives of this
thesis investigation were to measure the performance of the overland flow system
at Gordonsville Industries, Gordonsville, Virginia during cold weather operation,
to measure the performance of the system with an operational change, to assess
the response of the treated effluent to sand filtration, and to study the results
of soil moisture and soil tests.
Samples of the runoff were taken frequently during cold weather operation
of the raw waste and the runoff effluent, and were measured for chemical oxygen
demand, turbidity, percent transmission, conductivity, pH, and temperature. Soil
temperatures were measured , and daily weather records were acquired through the
state climatology office, to correlate with the results from the sample tests.
Runoff flow, in gallons per minute, during normal and split loading operation
was measured, and the treatea effluent was subjected to a series of tests
for alum precipitation, laboratory scale sand filtration, industrial scale mechanized sand filtration and sand filtration by a sand strip near the bottom of the terrace slope. Soil and soil moisture test results were collated and reviewed.
Re.sults from sample tests indicated that cold weather has a significant
effect on treatment performance, and that operation of the system can be
maintained during the winter, with a restriction for a low average air temperature
cutoff point of about 34 degrees Fahrenheit with a freezing soil temperature.
At these low temperatures the microorganisms perform aerobic oxidation
at a very restricted rate and evapotranspiration and percolation are also
reduced.
Results of the operation modification indicated that peak flow and peak
flow waste strengths can be reduced. Split loading gives the wastewater longer
time on the slope and increases the opportunity for oxidation by microorganisms,
filtration, adsorption, percolation, and evapotranspiration " Excluding the
mechanized filter, test results indicated that there is good potential for sand
filtration post-treatment of the runoff 1 because, the remaining color is mostly
"apparent" as a result of colloids in suspension. Test results of soil and soil
moisture do not indicate a ground water contamination problem.
Year-round textile wastewater treatment by overland flow is technically
feasible and can be enhanced by operation modifications and sand filtration
post-treatment without posing a ground water contamination problem.
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