# Water Supply Systems for Settlements with Arsenic-Contaminated Groundwater--Making the Right Choice
## 3 Results and Discussion
### Comparison of the Alternative Approaches
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & & & \multicolumn{3}{c}{**Investments**} & \multicolumn{3}{c}{**Operating Costs**} \\ \cline{3-8}
**Settlement** & **Population** & **Q Av.D**\({}^{*}\) & & **Total** & **Per Capita** & **Total** & **Per Capita** & **Per m3 of Water** \\ \cline{3-8}  & **m3/Day** & **(EUR)** & **(EUR/p.c)** & **(EUR/Year)** & **(EUR/p.c/Year)** & **(EUR/m3)** \\ \hline \hline \multicolumn{8}{l}{**Local supply systems for the 9 settlements in the Santa microsystem**} \\ \hline \hline \multicolumn{8}{l}{Municipality of Kanjiza} \\ Tresnjevac & 1724 & 327 & 454,000 & 263 & 41,500 & 24.1 & 0.35 \\ Adorjan & 1037 & 197 & 288,000 & 278 & 71,000 & 68.3 & 0.99 \\ Municipality of Senta & & & & & & \\ Bogaros & 568 & 117 & 285,000 & 502 & 56,000 & 98.8 & 1.32 \\ Gornji Breg & 1726 & 342 & 544,500 & 316 & 61,000 & 35.5 & 0.49 \\ Senta & 18,704 & 3946 & 4,166,500 & 223 & 874,000 & 46.7 & 0.61 \\ Municipality of Coka & & & & & & \\ Coka & 4028 & 721 & 1,598,000 & 397 & 230,000 & 57.1 & 0.87 \\ Sanad & 1151 & 205 & 525,000 & 456 & 75,000 & 65.0 & 1.01 \\ Ostojcevo & 2324 & 419 & 977,000 & 420 & 128,500 & 55.4 & 0.84 \\ Jazovo & 742 & 135 & 517,500 & 698 & 72,500 & 97.6 & 1.48 \\ Total & 32,004 & 6409 & 9,354,000 & 292 & 1,609,500 & 51.5 & 0.  
infrastructure is not less than 30 years, it can be concluded that, in this case, as a permanent solution, the central supply solution is the more economically favourable approach. It should be noted that the operating costs for any of the alternatives are not the total production costs of water but only its part. Among the major costs, the following were left out of our analysis: costs of water abstraction, secondary network, and the organisation of operations. For the entire territory of Kanjiza municipality, the following may be recommended:  
1. A central microsystem should be constructed for Kanjiza municipality, with water abstraction and a WTP in Velebit. 2. The system includes: Kanjiza, Velebit, Zimonjic, Martonos, Horgos, and Novi Knezevac
3. Drinking water treatment in the settlements Doline, Orom, Novo Selo, Totovo Selo, Male Pijace, and Mali Pesak should be resolved at the local level. A summary of all costs (investment and operating) for both alternatives for Senta is presented in Table 8. While the amount of investment is somewhat lower (about 7%, or an absolute difference of EUR 663,000) for the individual local water supply alternative, once again there is a very significant difference between the operating costs, which are far lower in the central microregional system (less than half as much, about EUR 678,000/year). The difference in annual operating costs exceeds the difference in the value of investments, such that after just one year, the centralised microregional system will already be more cost effective. Therefore, the centralised solution with the Senta microregional system is highly recommended. Investments amounting to EUR 313 per capita and operating costs of EUR 0.29 per cubic meter of produced water are quite acceptable. It should, however, again be noted that the above operating costs are not the total production cost of water but only a part of it, with the costs of water abstraction, secondary network and the organisation of operations left out of our analysis. From this comparison, it is clear that from an economic standpoint, the centralised approach to water supply is a significantly more viable solution for water supply in the two municipalities studied. This result is in agreement with the results of [PERSON] et al., who found that decentralised systems for water softening, although demonstrating sufficient treatment efficacy, were 7-10 times more expensive than centralised systems [24]. However, it should be noted that there are several sociopolitical issues that make realisation of the centralised approach harder to achieve:  
1. The vast majority of drinking water utilities in Serbia are public companies under the direct control of the municipalities.