Table 4: Changes in element concentrations in tap water after running the machine without feet.

Elements (μg/L)Pre-FBS ( 𝑛 = 4 )Post-FBS ( 𝑛 = 6 )Post-FBS–Pre-FBSP value
Mean ± Std devMean ± Std devDifference ± Std dev%change

Aluminum§93.75 ± 11.35105.00 ± 18.9514.17 ± 12.2215.10.257
Antimony§0.75 ± 0.501.83 ± 0.411.00 ± 0.63133.30.038
Arsenic§1.00 ± 0.005.50 ± 0.844.50 ± 0.84450.00.010
Barium§20.00 ± 0.0025.00 ± 5.485.00 ± 5.4825.00.333
Boron35.00 ± 5.7736.67 ± 5.163.33 ± 5.169.50.905
Cadmium§0.50 ± 1.006.50 ± 1.645.50 ± 2.431,100.00.010
Calcium39,255.00 ± 1,354.5139,843.33 ± 906.151,206.67 ± 893.373.10.609
Chromium3.50 ± 1.2917,289.67 ± 4,240.3617,286.67 ± 4,239.65493,904.70.010
Cobalt1.00 ± 0.00249.17 ± 44.02248.17 ± 44.0224,816.60.010
Copper465.00 ± 46.55723.33 ± 93.31253.33 ± 64.3954.50.010
Iron213.50 ± 183.7288,689.17 ± 17,460.5988,388.17 ± 17,532.1141,399.60.010
Lead§2.75 ± 1.713.17 ± 1.170.33 ± 1.3712.10.676
Lithium0.00 ± 0.001.17 ± 2.861.17 ± 2.860.00.800
Magnesium10,720.00 ± 437.3411,025.00 ± 561.31405.00 ± 427.733.70.476
Manganese5.25 ± 0.501,240.17 ± 212.041,235.00 ± 211.8323,523.80.010
Molybdenum47.50 ± 18.362,559.83 ± 440.072,505.17 ± 438.105,274.00.010
Nickel3.25 ± 2.5011,623.17 ± 2,076.0311,621.00 ± 2,075.55357,569.20.010
Phosphorus16.75 ± 15.7348.50 ± 28.0337.33 ± 21.73222.90.114
Potassium2,052.50 ± 235.282,146.67 ± 190.23−11.67 ± 163.64−0.60.610
Selenium0.75 ± 0.500.50 ± 0.550.00 ± 0.000.00.905
Silicon742.50 ± 120.931,805.00 ± 204.521,003.33 ± 170.37135.10.010
Silver§0.00 ± 0.000.00 ± 0.000.00 ± 0.000.00.000
Sodium77,622.50 ± 41,701.87101,911.67 ± 9,916.6919,190.00 ± 38,454.8824.70.114
Strontium200.50 ± 4.80202.83 ± 7.883.17 ± 10.941.60.114
Sulfur6,245.00 ± 1,537.156,178.33 ± 1,234.35−628.33 ± 1,253.99−10.10.914
Uranium§0.00 ± 0.000.00 ± 0.000.00 ± 0.000.00.000
Vanadium1.00 ± 0.0043.50 ± 11.7142.50 ± 11.714,250.00.010
Zinc22.50 ± 9.5735.00 ± 17.6116.67 ± 10.3374.10.543

Total137,771.75 ± 43,704.77285,799.67 ± 27,823.80142,837.17 ± 36,748.30103.70.010

Array components1,481.50 ± 334.61124,179.50 ± 24,547.41122,540.83 ± 24,659.988,271.40.010
Essential elements136,171.50 ± 43,506.28161,473.17 ± 10,605.2120,265.83 ± 39,878.1514.90.171
PTEs§118.75 ± 11.53147.00 ± 25.4230.50 ± 19.8525.70.133

§PTEs: potentially toxic elements were defined to be aluminium, antimony, arsenic, barium, cadmium, lead, silver, and uranium.
Essential elements were defined to be boron, calcium, lithium, magnesium, phosphorus, potassium, selenium, sodium, strontium, sulphur, vanadium, and zinc.
Array components were defined to be chromium, cobalt, copper, iron, manganese, molybdenum, nickel, and silicon.
Bold indicates a statistically significant difference, 𝑃 < 0 . 0 5 (Mann-Whitney U-test).