Hardness

Degree of hardness for all results are in between 0 to 75mg/L. Hence, they fall within the acceptable range.

The hardness of water in Inlet C1 is the highest, the grease trap being the second highest. This is due to the detergent or soaps containing hardness-causing ions in the Grease Trap.

From the grease trap, the water travels through the phytoremediation system(PS) which contains soil, stones and plants. Perhaps the calcium ions from the stones gets washed away by the water passing through the PS and a large concentration of hardness-causing calcium ions ends up in the water of Inlet C1, resulting in the high value for hardness.

Laboratory Testing

· COD
1) The sample is refluxed with known amounts of potassium dichromate and sulphuric acid.
2) The excess dichromate is measured by spectrophotometry, as the amount of organic matter is proportional to the potassium dichromate consumed.

· Phosphate
1) Ammonium molybdate is combined with the sample containing phosphate ion and form a yellow colour solution
2) A reducing agent, ascorbic acid is added to produce a blue colour solution that is proportional the amount of phosphate present.

· Hardness
1) EDTA, a tritrating agent is added into the sample.
2) Hardness is present if the dye turns reddish-pink from blue colour.

· Suspended Solids
1) Weigh the filter paper with the ceramic dish.
2) Filter paper is placed on the filtration unit and a sample vessel is attached to filter assembly.
3) The filter paper is left to dry in the over at ±105®C for an hour in the oven
4) Then it is being measured again for the amount of solids on the filter paper

· Chloride
1) An indicator, potassium chromate is added into the sample
2) Silver nitrate is used as a titrant in the process of titration.
3) The titred value is noted when the solution turns reddish-brown and calculated by the formula.

Hardness vs TDS

There is no correlation between the hardness and total dissolved solids content of the different water collection points.

This would mean that the bulk of the total dissolved solids did not consist of hardness-causing cations and anions like Calcium, Magnesium, Carbonates and Bicarbonates.

To prove this further, the hardness of our control (Tank before Pond) was one of the higher ones despite having a TDS concentration of 0mg/L.