Economic substantiation of use of sodium hipochlorite for water treatment of swimming pools

                                                                          A. Istoshin

Introduction

At an estimation of a degree of risk to health of the person the most important role is played with microbiological pollution of water. Receipt in a swimming pool of microbes and pathogenic bacteria occurs owing to poor quality of processing of water at stations of the centralized water-preparation, pollution of basin occurs from visitors during operation. Water of poor quality can cause a number of illnesses, especially if the head of the swimmer is often diped: adenoviral pharingo-conjunctival a fever, an epidermophitia (« an itch of swimmers»), virus hepatites A and many other things.
For exception of probability of occurrence of flashes of infectious diseases water of basin it is necessary to subject disinfection.
Earlier, in processes of disinfection of water, chlorine-gas was used. Now this method is not used owing to weighable restrictions on safety.
Now, to a problem of disinfection of water of basins are applied:
- the various chemical combinations, allowing to obtain disinfecting agents at disolution in water;
- disinfection by dioxide of chlorine (ClO₂), obtained from sodium chlorite (NaClO₂);
- Disinfection by sodium hipochlorite (NaClO), obtained electrolysis of chloride of sodium (NaCl).
For definition of investment appeal of offered technology of disinfection of water by electrolytic sodium hipochlorite it is necessary to carry out comparison of cost of water treatment of basin of unit volume (for example, volume 2000 м³), the methods listed above.

Hygienic requirements to quality of water of swimming pools

According to recommendations of standards of the various countries residual concentration of active chlorine in water of a swimming pool not should to exceed 3 mg/litres (tabl.1).

Table 1

The note: ^a PWTAG (1999), ^b Recommended European Community values; PWTAG (1999), ^c American National Standards Institute (1991), ^d Deutsches Institut fur Normung (1997), ^e Gazzetta Ufficiale della Repubblica Italiana (1992), ^fSanPIN 2.1.2.1188-03 (2003).

The technical and economic analysis of disinfection of water of pools

According to the data presented in table 1 concentration sodium hipochlorite in water of a swimming pool should not exceed 3 mg/litres. Thus, for disinfection of water of pool (from medium dirtiness of water organic compounds) volume 2000 м³ 6 kg/day of sodium hipochlorite (2,0 kg/day of dioxide of chlorine - is required smaller concentration) is required.
Annual charges on disinfecting of water include: amortisation charges and working costs on: the electric power, reagents, replacement of materials.
Amortization also includes charges on repair, rent and the maintenance of a premise, a payment on service of installation, taxes and the other fixed charges which depend only on productivity of installation. This kind of expenses is difficult for estimating in advance as they basically depend on an external environment of installation on the yielded concrete place, therefore these expenses are not included in calculation.
In table 2 expenses for disinfection of water of pool, by volume 2000 м³, various methods are presented.
Table 2

Summing up the review of the market of technologies of systems of water-preparation, it is possible to draw a conclusion - application of the concentrated reagents and dioxide of chlorine for disinfection of water of pools  is poorly perspective, as expenses for processing of water (for the first year of operation) in 2,0 and 1,72 times above, than in case of use of electrolytic sodium hipochlorite.
On fig. 1 expenses (in euro) on disinfection of water of pool in volume 2000 м³ for five years of operation are presented.

Fig.  1 Expense for disinfection of water of pool in volume 2000 м³ for five years of operation: 1 - chemical reagents, 2 - Bello Zone, 3 - Szelena2 Bt.