Arsenic Removal by Sand Filtration for Potable Water in Newfoundland

Coles, Cynthia and Bin Rohail, Danial (2012) Arsenic Removal by Sand Filtration for Potable Water in Newfoundland. Project Report. The Harris Centre, St. John's, Newfoundland and Labrador.

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Abstract

The purpose of this research was to study sand filtration as a treatment technology for drinking water sources in Newfoundland and Labrador to reduce the arsenic (As) concentration to the level of 7 micrograms (µg) per litre without using chemicals. The effect that various ions present in groundwater have on As removal efficiency using sand filters was also investigated. Water sampling locations were narrowed down based on the composition of groundwater provided by the Department of Environment and Conservation. Two different water samples were collected from the town of the Wabana on Bell Island. One with high As and iron (Fe) concentrations and the other the normal Wabana water supply. Water samples were also collected from the Town of Freshwater in Carbonear. The composition of the water samples (arsenic, iron and other element concentrations) was determined using Inductively Coupled Plasma Mass Spectrometry (ICPMS) from the Department of Earth Sciences at the Memorial University of Newfoundland. The Fe to As ratio is the most important parameter in successfully removing arsenic from groundwater to the level below an acceptable concentration. Capital Ready Mix supplied the washed sand required for this project. The sand had a finesse modulus (FM) of 2.9. The sand for all the experiments was first washed with 60˚C hot distilled water to dissolve all the impurities. The water was then drained to collect the washed sand. The sand was dried in the oven at 105˚C for 24 hours to remove all the moisture. Batch Column tests were conducted for treating the arsenic contaminated water. The test equipment, two columns, was manufactured by Technical Services in the Faculty of Engineering and Applied Sciences. The columns were partially filled with the washed and dried sand. In order to uniformly distribute the water along the whole cross section and to control the flow of solution into the column, either a Ceramic disk or the cloth was used. Similarly, at the bottom of the column, either the ceramic disk or cloth was used. The purpose of using either the ceramic disc or the cloth at the bottom of the column was to allow the flow of the solution out of the column and to retain the sand. 1000mL of distilled water was passed through the column prior to commencing the batch tests to remove all the very fine particles which results in turbidity. Once the clear water was collected at the bottom of the column, only then the tests were initiated. It was concluded that hydrous ferric oxide (HFO) can play a very vital role in mitigating the arsenic concern in the groundwater of the Newfoundland and Labrador. The higher the iron content, the greater will be the arsenic removal but the sand filter replacement frequency may decrease. It is therefore suggested to use sand filtration in combination with aeration and dilution to deal with the growing arsenic concern in the province of the Newfoundland and Labrador.

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