Saman Nimali Gunasekara
Master’s Thesis: Improvements on Municipal WWT
are 4.11% at 30 mg/l [Ca2+] and 10 mg/l of [Mg2+] and 0.66% at 30 mg/l [Ca2+] and 40 mg/l of [Mg2+]. The detailed experimental results are available in TableA4 0.1, while the percentage increase results for conductivity are available in TableA4 0.4 in Appendix 4. 4.3.1.6 Alkalinity The percentage alkalinity increase of the wastewater considering the before and after treatment alkalinity measurements, is depicted in Figure 4.10. Since alkalinity was being measured in only one of the two parallel experiments (referred to as the main trial), only the measurements for this trial is representative of the results in the figure, while the labelling is similar as mentioned in Section 4.3.1.1. 15,000 10,000
% Alkalinity Increase
5,000 0,000 -5,000
10
20
30
40
[Ca2+]= 10 [Ca2+]=20
-10,000
[Ca2+]=30 -15,000 -20,000 -25,000 -30,000 -35,000
Mg2+ Concentration (mg/l) Figure 4.10 Percentage increase of alkalinity vs. Mg2+ concentration (only for main trial)
No distinct common trend could be identified for the increase (or decrease) of alkalinity with the increase of Mg2+ for constant Ca2+ concentrations, or even for increasing Ca2+ for constant Mg2+ concentrations. However at 30 mg/l of Mg2+ for all the three concentrations of Ca2+, the percentage increase is somewhat closer in values; nevertheless within a range of around 5% with two values lying at negative range thus actually being percentage reductions. For Ca2+ concentration 10 mg/l, the percentage increase is increasing with the increase of Mg 2+ concentration, while for both the other concentrations of Ca2+ the percentage increase is somewhat deviating, increasing up to a maximum, then decreasing to a minimum and then again increasing (in a zigzag pattern) when the Mg2+ concentration is increasing. A distinct feature is that alkalinity increase for the two concentrations of Ca2+, 20 mg/l and 30 mg/l; are quite similar at each corresponding Mg2+ concentration except at 10 mg/l (where in contrast there is a huge deviation in the two values as well as in sign, one being positive and the other negative). The highest alkalinity increase; 9.33% is observed at 10 mg/l of [Ca2+] and 40 mg/l of [Mg2+]. A distinction in alkalinity measurements also was the observations that not only increases but also - 44 - | P a g e