# Water Quality Changes in Cement-Lined Water Pipe Networks
## 4 Summary  
The aim of this research was to examine the impact of cement-mortar lining covering the interior surfaces of ductile iron water conduits on the quality of water conveyed in these conduits. Tests were performed using an experimental setup made of commercially available pipes. The setup was supplied with underground water collected and provided, without treatment, to a water supply network in a mid-sized city. Water examined during the experiment was of variable quality, however for the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Element** & **Unit** & \begin{tabular}{c} **Water Feeding** \\ **the Setup** \\ \end{tabular} & \
\begin{tabular}{c} **Water after 32 h** \\ **of Stagnation** \\ \end{tabular} & **Increment** & **Increment (\%)** &
\begin{tabular}{c} **Limit Value for** \\ **Drinking Water** \\ \end{tabular} \\ \hline B & ppb & 18.1 & 21.6 & 3.5 & 19 & 1000 \\ Na & ppm & 9.9 & 10.8 & 0.9 & 9 & - \\ Mg & ppm & 17.7 & 17.8 & 0.1 & 1 & 125 \\ Fe & ppb & 366.4 & 399.6 & 33.2 & 9 & 200 \\ Zn & ppb & 8.5 & 26.9 & 18.4 & 217 & - \\ Ga & ppb & 1.9 & 2.1 & 0.2 & 12 & - \\ Ba & ppb & 21.7 & 22.6 & 0.9 & 4 & 700 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Concentrations of trace elements in the water after 32-h stagnation in the cement-lined pipe (after 8 months in service). entire period of the experiment it displayed good physico-chemical properties in terms of its fitness for consumption, as well as poor corrosive properties with a tendency to form protective coatings, which made it a minor hazard for cement and metallic materials. During the experiment, attempts were made to determine changes in the physico-chemical quality of the water during long-term (multiple day) and short-term (few hours) stagnation of the water in the setup and during its flow through the setup at the velocity of 0.1 m/s (which is typical of working water supply networks). While examining the impact of cement mortar lining on water quality, changes in the quality in terms of increased indicators such as primarily turbidity, pH, alkalinity, hardness, chloride, sulphate and dry residue content were reported, as well as reduced carbon dioxide water content. Values of indices characterising water stability pointed out that water introduced into the setup gradually lost its corrosive properties and acquired an increasing ability to precipitate calcium carbonate. This provided evidence of the penetration of components of the cement lining into the water. Such changes were recorded incrementally for the first 5 weeks of water contacting the cement lining. After shorter contact (up to 32 h), water quality changes were primarily related to increased turbidity and hardness and minor pH rise. The phenomenon of interaction between water and cement-mortar lining was also observed while testing the water flow through the setup at the velocity of 0.1 m/s. In this case, the change in water quality was very small. It did confirm, however, the leaching of cement components into the water, which raised the water's ability to precipitate calcium carbonate. In the experiment, besides changes in the typical water quality indicators, an attempt was made to determine water penetration by metals found in the cement-mortar lining due to the applied cement manufacturing method. While testing the sample collected from the cement-mortar lining, besides the primary cement components, the following trace elements were detected: iron, magnesium, manganese, zinc, barium, chromium, lead, nickel and cobalt. Analyses conducted of samples of chlorinated and non-chlorinated water having contact with the cement lining at the initial stage of setup operation failed to confirm penetration of significant amounts of trace elements into the water (whereas leaching out of trace elements from cement was more intense in chlorinated water).