Analysis of Filtered Water for Barium

Attached is the first part of the report from  Dr. Kingsley Donkor and Megan Campbell of the Thompson Rivers University Chemistry department analyizing water from the first of two filters that were brought to be evaluated for the possiblility of problems with Barium in clay used to form filters. These results are for the new 100% Plainsman red earth filter. You can read the report but essentially even analysis of a un flushed filter shows the barium level to be one third of the allowable limit initially and then  reduced to one third of that level very quickly.

Analysis of Filtered Water for Barium

Analyst: Megan Campbell, B.Sc.

Supervisor: Dr. Kingsley Donkor

Thompson Rivers University, Kamloops, BC

December 24, 2009

Method
Standards were made with barium chloride hydrate (BaCl2•2H2O) to produce a calibration curve as seen in Figure 1.  The barium standards ranged in concentration from 0 – 10 ppm, in increments of 0.5 ppm.  Each standard was analyzed in triplicates.

Tap water was filtered through a new 100% Plainsman red earth filter and samples were taken at 1.5, 2.5, 5 and 7.5 hours.  The samples were collected in brown washed plastic bottles.  Aliquots of 100 mL of each of the samples were taken and analyzed in triplicates.

Atomic absorption spectrometry (AAS) was used to analyze the concentrations of barium in the standards and in the filtered water which allowed for the determination of barium in each of the filtered water samples collected.

To ensure optimum results, the following precautions were performed:  The filtered water samples were collected in acid washed bottles that were washed in diluted (1:3) nitric acid to prevent interference by contamination.  Also, in each of the standard barium solutions and collected filtered water, potassium nitrate (KNO3) was introduced to suppress ionization.

Results
A calibration curve was made from the analysis of barium chloride hydrate by AAS (Figure 1).  From this calibration curve, the concentrations of barium in the filtered water samples at the different time intervals were determined as seen in Table 1.

Figure 1.  The calibration curve of barium using AAS.

*ppm = µg/mL or mg/L

Table 1.  The concentrations of barium in the filtered water samples at the different times of collection.

*ppm = µg/ mL or mg/L

Discussion

From the calibration curve produced by the barium chloride hydrate standards, the unknown concentrations of barium in the filtered water samples were determined.  The highest concentrations of barium were observed in the samples taken after 1.5 hours of filtration with an average barium concentration of 0.3154 mg/L (ppm) (Table 1).  With increasing time, the concentration of barium decreased in the filtered water indicating less barium was leaching into the water.  These results correlate with the physical properties observed when the water samples were collected.  At 1.5 hours, the water was an orange/yellow color and had a strong ceramic odor.  The following samples taken at 2.5, 5 and 7.5 hours gradually became colorless and odorless.  From these observations, it can be seen that less of the ceramic filter make-up is leaching into the filtered water; therefore, less barium is too. From the Health Canada’s Guidelines for Canadian Drinking Water Quality, the maximum acceptable concentration of barium in drinking water is stated to be 1 mg/L (1 ppm ) [1].  The barium concentrations experimentally obtained from the filtered water are exceptionally lower than the maximum acceptable concentration of barium in drinking water.  The highest average concentration of barium was after 1.5 hours and is approximately three times lower than the accepted concentration of barium in drinking water.

Reference

1. Electronic Resource, http://www.saskh20.ca/PDF-WaterCommittee/Barium.pdf