It is essential to preserve the quality of natural mineral water from its origin to the points of use, so as to ensure sanitary safety for patients within the thermal spas. The complexity of water systems may lead to issues linked to microbiological and physico-chemical contaminations which are necessary to be solved in order to keep the installations in compliance with the regulations in force. In order to provide the thermal spa sector with means to achieve this goal, the team at the Institut du Thermalisme – Bordeaux University aimed at finding a relevant solution, i.e. designing and making two original and innovating prototypes which reproduce – in miniature – the natural mineral water system we can find in thermal spas. These two prototypes are different due to the nature of the materials they are made of. It is possible to get significant improvements in the research: on the one hand, linked to the general working of a thermal water system connected to individual or collective care units and, on the other hand, improvements in the research on keeping the quality of natural mineral water. Also, to solve microbiological and physico-chemical contamination issues, chemical and thermal treatments can be used.

INTRODUCTION

In the frame of the enforcement of rules relating to the management of microbial risk in French thermal spas (Arrêté du 19 juin 2000 modifiant l'arrêté du 14 octobre 1937 modifié; Circulaire DGS/VS 4 N° 2000-336 du 19 juin 2000; Arrêté du 27 février 2007; Décret n° 2007-49 du 11 janvier 2007), and which imposes the use of natural mineral water (NMW) free from bacteria at resource and at points of use, the Institut du Thermalisme – Bordeaux University (France) proposed efficient technical means to tackle to issues of the thermal spa sector.

Hence two prototypes (or pilots) of semi-industrial size were created. They reproduce the configurations of natural thermal mineral water systems. One is made in stainless steel grade 316 L and the other one in chlorinated polyvinyl chloride (C-PVC). They were designed so as to investigate the following:

  • The overall functioning of a thermal water system in order to preserve the quality of NMW, from its source to the point of use (treatment units), from physico-chemical and microbiological points of view.

  • The overall functioning of a swimming pool (tank), as it is connected to one of the two pilots (stainless steel 316 L or C-PVC), supplied with NMW so as to comply with the criteria on hydraulic, sanitary and other conformities, as stated by the regulations in force.

  • The various types of materials commonly used for pipes: stainless steel 316 L and C-PVC.

  • The various items constitutive of a system: valves, solenoid valves, variable flow pump, dosing pump, plate exchangers, manometer, thermometer, storage tank, heating system, etc.

  • The various types of physical or chemical treatments as part of preventive or curative maintenance operations.

This work thus presents the pilots which were designed by the laboratory of the Institut du Thermalisme, as well as the various applied studies which are carried out there.

MATERIALS AND METHODS

The two pilot designs testify for the need for applied research in balneology, hence the works of the Institut du Thermalisme on bibliography-poor topics. The pilots designed and described hereafter are the result of the thinking and expertise that are shared with university teachers and researchers (S. Pécastaings, Toulouse University – France; J.L Legido Soto, Vigo University – Spain), professionals, design offices, etc., of the sector.

The stainless steel 316 L prototype

The stainless steel 316 L prototype (Figure 1 and Figure 2) with the following measurements: L = 3.70 m, l = 1.40 m, H = 2.40 m, is attached to a wheeled frame enabling to foresee on-site testing, particularly in the thermal spa centers.
Figure 1

Synoptic diagram of the stainless steel 316 L prototype.

Figure 1

Synoptic diagram of the stainless steel 316 L prototype.

Figure 2

Stainless steel 316 L prototype.

Figure 2

Stainless steel 316 L prototype.

It is entirely made with AISI (American Iron and Steel Institute) stainless steel 316 L (17% chrome, 10.3% nickel and 2.1% molybdenum). This steel is preferentially used for the creation of NMW system in thermal spa but also used in health centres. It perfectly withstands high temperatures and most chemical treatments (CSHPF 1999) except hypochloric acid and high concentration chlorine (circulaire du 19 juin 2000).

The prototype may be supplied in NMW or tap water. This water is then stored in a 500-litre stainless steel tank (Charot – ZI des Sablons – BP166 - 89101 Sens Cedex France: stainless steel 316 L, 0.5 m3, 6 kW, reference 2558), the aim of which is to store and totally disconnect the pilot from the main system, hence protecting it from a potential retro-contamination. The storage tank is also equipped with an adjustable heating resistance making it possible to withstand thermal shocks (over 70 °C) for disinfections or to maintain temperature (around 35 °C for rheumatology treatments, 27 °C for phlebology treatments).

The thermal water flow is made possible with a variable flow pump (from 2 to 6 m3 per hour) which is correctly sized (Wilo Salmson France - 53 Bd République - 78400 Chatou: Salmson multi VE 204 EXV T4 2-2G).

In order to get a thermal water at respectively 35 ± 1 °C and 27 ± 1 °C for rheumatology and phlebology purposes, two plate exchangers (CIAT - 700 Avenue Jean Falconnier – BP14 - 01350 Culoz – France: PWA18.11 with 10 plates, 186 kW and PWA6.11 with 15 plates, 58 kW), correctly sized as well, are set in series on the pilot.

A pipe dead-leg, real reserve of stagnating water, was created after the plate exchangers so as to study the links which may exist between the hydraulic conceptions defects and the formation of biofilm and/or bacterial development. As a matter of fact, Donlan showed in 2002 that any material immersed in a stagnating water-based environment is immediately covered by polymers forming the conditioning film, a medium to which the bacteria may stick. The biofilm may be defined as the association of a bacterial community with a surface, included in a polymeric extracellular matrix (Costerton et al. 1995; Costerton 2004; Vu et al. 2009) or only characterised by an inter-bacterial adhesion (Palmer et al. 2007).

The water then flows in the detachable part of the prototype – initially in stainless steel 316 L – on which various types of piping materials (C-PVC, galvanized steel, copper, etc.) may be added so as to study the biofilm development/material ratio (Enkiri et al. 2006; Labbé et al. 2008; Chauveheid & Hansen 2010; Allion et al. 2010).

In 2006, Enkiri developed a study on many materials (copper, C-PVC, stainless steel, polybutene and polypropylene) at 30 °C and 50 °C, which proves that the capacity to generate the formation of biofilm varies according to the nature of the material and the temperature. Some metallic materials (stainless steel, copper) or organic (C-PVC) generates little biofilm while others (polypropylene, polybuthene) lead a proliferation of microorganisms. It should be noted that this study was made on new materials and that it takes into account by no means the ageing of the material, its scaling, corrosion and the disinfection procedures.

Regarding the water compatibility/material ratio, it is noticeable that the choice of the material will be of utmost importance for NMWs with physico-chemical profiles that are abrasive for the piping (CSHPF 1999; Arrêté du 29 mai 1997; Circulaire n° 2000-232 du 27 avril 2000 modifiant la circulaire DGS/VS4 99-217 du 12 avril 1999); the example of strong mineral waters (conductivity > 2000 μS/cm) containing chloride and sodium from Salies de Béarn (France, 64) are a very revealing example for which the most adapted material is C-PVC. On the other hand the natural mineral waters from Dax (France, 40) containing sulphate, calcium and magnesium are most of the time piped in stainless steel 316 L systems.

Finally the water is:

  • either rejected to the sewage system if the pilot is run in open circuit;

  • or directed to the storage tank so as to be re-used or re-directed to a pool (like a swimming pool) with a connexion at the output of the first exchanger, when the system is run in closed circuit.

Moreover, the pilot is fitted with various control devices (manometers, flowmeters, thermometers) making it possible to know the pressure, flow and temperature parameters, which may have an incidence on bacteria or a biofilm development observed by moving pipes (seen through removable piping).

Eleven sampling taps also fit the prototype so as to get samples and thus analyse the water at strategic locations of the system: at the output of the storage tank and then before and after the pump, the two exchangers and each piping to be tested. Their locations were tested to provide a precise knowledge of the microbiological quality of the thermal water, or of any water, on any critical points of the pilot.

Four transparent pipe sections are laid all along the system and used as check pipes for the overall state of corrosion and scaling of the system.

In addition, this pilot is fitted with a dosing pump that is connected to the tank (ProMinent France SA – 8 Rue des Frères Lumière – BP39 - Eckbolsheim – 67038 Strasbourg Cedex 2: ProMinent Gamma/L GALA 1005 NPB VA 01 0000) and that may be used for chemical disinfection operations of the system.

Finally, an electrical control cabinet is connected parallel to the system and manages the electricity supply of the storage tank, the solenoid valves, the pump and the two exchangers.

C-PVC prototype

As for the stainless steel 316 L prototype, the C-PVC prototype (Figure 3 and Figure 4) is made with slightly different dimensions (L = 3 m, l = 1.90 m, H = 1.40 m) and is assembled on a frame with four casters so as to be used for experimentation in thermal spas.
Figure 3

Synoptic diagram of the C-PVC prototype.

Figure 3

Synoptic diagram of the C-PVC prototype.

Figure 4

C-PVC prototype.

Figure 4

C-PVC prototype.

All its constitutive items are made of C-PVC, with the exception of the plate exchanger, which is made in stainless steel. Some simplifications were added compared to the stainless steel 316 L prototype: removal of one plate exchanger, of the pipe dead-leg and of the removable part.

The NMW (or any other sort of water like tap water) is stored in a C-PVC storage tank (Linpac Allibert – 5 Rue Montesquieu – 92018 Nanterre cedex) with a 500-litres capacity and fitted with a cover and a removable electrical resistance (Vulcanic SAS – 48 Rue Louis Ampère – Zone Industrielle des Chanoux F – 93330 Neuilly sur Marne – France: Type 4832, 9 kW, stainless steel 316 L). Chemical corrosive disinfections are thus made possible with no risk of damaging the resistance. The water is flown into the system through a pump which is entirely made of C-PVC, pump housing included (Someflu – BP72 – F 93172 Bagnolet cedex: Someflu Eco-N 32/200 PP). The water can flow through two different paths:

  • Either the hot mineral water flows through the whole system as it undergoes a cooling through the plate exchanger (CIAT - 700 Avenue Jean Falconnier – BP14 – 01350 Culoz – France: PWB8.11 033P). Using the principle of calories exchange, this exchanger uses cold tap water to lower the water temperature to the desired temperature according to the identified thermal spa indication. The cooled water will thus go back to the storage tank or be directed to the sewage system.

  • Or the hot mineral water by-passes the plate exchanger to get back directly to the storage tank, when the prototype is used in closed circuit applications and the water is directed to the sewage system.

Three hundred and eighty volts may supply the prototype with two electrical control cabinets. The first box manages only the electrical resistance in the tank which is used:

  • either to heat the cold tap water to approximately 70 °C, during 30 minutes, so as to create thermal shocks for bacterial eradication;

  • or to select a constant temperature of the water for individual or collective uses (35 °C).

The second electrical control cabinet manages several devices: the recirculation pump, the dosing pump and the four solenoid valves of the system. The two first solenoid pumps located at the input point of the tank alternatively enable the prototype to run with thermal water or with tap water as they open or close. The control of the water volume in the tank is made with two filling probes located on a high position and a low position of the tank.

As for the solenoid valve at the end of the exchanger, it plays the role of temperature control so as the water temperature at this point is in compliance with the requested instruction. Finally, the last solenoid valve is located downstream of the tank and enables the prototype to run in closed circuit with a recirculation of the water to the tank, or in open circuit with a disposal of the water to the sewage system.

Moreover the prototype is fitted with manual control items all along its system: three manometers, two flowmeters, one thermometer and twelve valves. In addition, as on the 316 L stainless steel prototype, a dosing pump (ProMinent France SA – 8 Rue des Frères Lumière – BP39 – Eckbolsheim – 67038 Strasbourg Cedex 2: ProMinent Gamma/L GALA 1005 NPB VA 01 0000) may be connected to automate the chemical disinfection on the system. Lastly, six sampling taps make it possible to study the sanitary aspect of the system.

Connecting the pilots to an experimental pool

Each pilot (stainless steel 316 L or C-PVC) can be connected to an experimental pool holding 2 or 3 m3 at the exit of the plate exchanger ‘35 °C’, thus creating a pool pilot (Figure 5) equipped with a water processing station (Figure 6), which is made of a recirculation pump, a 6-way sand filter, a chlorinator and a chlorine regulator (equipment manufacturer: SWAN) with a solenoid valve. The pools (2 or 3 m3) are fitted with 8 multidirectional discharge nozzles. As for the mandatory disposal of the water top layer, the 2 m3 pool (Figure 7) is fitted with a skimmer whereas the 3 m3 pool (Figure 8) is fitted with a channel, evacuating the organic pollution brought by the bathers much more homogenously.
Figure 5

Synoptic diagram of the pool prototype.

Figure 5

Synoptic diagram of the pool prototype.

Figure 6

Water processing station.

Figure 6

Water processing station.

Figure 7

2 m3 pool.

Figure 7

2 m3 pool.

Figure 8

3 m3 pool.

Figure 8

3 m3 pool.

Applications of those prototypes

The aim of the designing of these two pilots was to maximize the disinfection methods and to suggest realistic solutions for the thermal spa sector through tests, some of which were published in scientific literature (Pécastaings 2010); other tests were carried out, yet remain unpublished.

There are two sorts of applications for these prototypes.

  • Either the system flows in closed circuit and two applications are possible:

    • Test the efficiency of chemical and/or physical treatments after an artificial bacterial contamination through challenge testing.

    • Test the efficiency of chemical treatments after adding organic nitrogen and bacterial pollution coming from bathers in a swimming pool.

  • Or the system flows in open circuit and two sorts of applications are also possible:

    • Test with a water disposal to the sewage system.

    • Or test with a connection to an individual care unit.

RESULTS – DISCUSSION

The two prototypes in the Institut du Thermalisme have the same applications but the physico-chemical profile of the mineral water and the types of treatments applied on the systems will lead us to choose between the two. Hence, for a NMW having high chloride and sodium characteristics, as we may find with the mineral waters from Salies de Béarn in the Pyrénées Atlantiques (France, 64), it will be mandatory to use the C-PVC prototype so as to avoid corrosion phenomena met with stainless steel 316 L. Besides the C-PVC pilot could be of perfect use in the thalassotherapy sector as waters are highly loaded with chloride and bromide.

Similarly, the chemical treatments of the ducts will have to take into account the material/product compatibility and the product concentration applied according to the recommendations of the Conseil Supérieur d'Hygiène Publique de France (French Public Hygiene Higher Council) (CSHPF 1999; Circulaire DGS/SD7A/SD5C/DHOS/E4 n° 2002/243 du 22 avril 2002 relating to the prevention of Legionella hazard in health centres).

It is also essential to take into account the very rigorous sanitary rules that are mandatory for the thermal water spa sector in France. It is compulsory to have an absolute absence of pathogenic bacteria (Circulaire DGS/VS 4 N° 2000-336 du 19 juin 2000) on points of use; otherwise care units, distribution units and even the whole thermal spa centre may be shut down. There are two sorts of pathogenic bacteria which are researched in the frame of this check:

  • Bacterial indicators of fecal contamination: total coliforms, thermo-tolerant coliforms (including Escherichia coli), enterococci, sulphite-reducing anaerobic bacteria.

  • Other pathogenic species: Pseudomonas aeruginosa and Legionella pneumophila.

Pathogenic staphylococci are also checked in collective cares thermal water pools (Arrêté du 7 avril 1981; Arrêté du 18 janvier 2002 modifiant l'arrêté du 7 avril 1981 modifié; Arrêté du 22 octobre 2013).

In this context, we can present results on our tests we have realized in closed or open circuit.

Case studies in closed circuit:

  • The stainless steel 316 L, used in closed circuit, made it possible to study the Pseudomonas aeruginosa strains. This ubiquitous bacterium is frequently met in thermal spas with a colonisation of the water systems and with its capacity to create biofilms prone to host Pseudomonas aeruginosa (Klausen et al. 2003).

  • The system thus got artificially contaminated at the tank level by these environmental Pseudomonas aeruginosa strain with a 8.05 × 108 CFU/mL (colony-forming unit/mL) concentration (challenge test method). Then the contaminated water was flowed during approximatively 1.30 hours. After a stagnation period lasting nearly 12 hours, the system was drained and the pilot filled with mineral water. Disinfection tests have been performed following two methods (Pécastaings 2010):

  • • a chemical process using a thermal shock with various active products: polyhexamethylene biguanide (PHMB) (25, 35, 250 ppm, 1 hour, NF EN 1040 standard), bleach with 9.6% chlorine (1, 10 and 50 ppm, 1 hour), Sanosil® (hydrogen peroxide H2O2 + silver nitrate 500 and 1,000 ppm, 1 hour).

  • • a physical process through thermal shocking, 1 hour at 80 °C.

  • Still with the same goal in mind, i.e. the eradication of Pseudomonas aeruginosa biofilms, the stainless steel 316 L pilot system was used in closed circuit to test the efficiency of a magnetic electro frequencies generator, producing low magnetic frequencies under 300 Hz (SPECTRUM® G3 generator). It was developed and patented in 2005 by the firm SPECTRUM Ingénierie (review: L'eau, L'industrie, Les nuisances, n° 333, 2010).

  • Once connected to an experimental pool, this pilot made it particularly possible to do disinfection tests with sodium hypochlorite for rheumatology thermal pools, which are supplied by Dax natural mineral water (containing sulphate, calcium, magnesium and light sodium) (Dubourg et al. 2008).

  • Moreover, Cleaning In Place (CIP) comparative tests were undertaken on the two stainless steel 316 L pilots with the classic protocol: de-greasing at pH 12 with soda and then descaling at pH 3 with diluted nitric acid, followed by a neutralization and rinsing (results not published yet).

  • As for the C-PVC pilot that is connected to an experimental 3 m3 pool, we tested it on the Isla de la Toja site which is located in Galicia (Spain). This NMW contains calcium, magnesium, much chloride (>16 g/l) and it has high conductive (>20000 μS/cm).The study of this corrosive water, that is disinfected with the biocide bromochloro-5,5-dimethyl hydantoin (BCDMH), which is approved in Spain, shows the C-PVC pilot reacts very well to this corrosive water.

Case studies in an open circuit:

  • Several test trials were made on the stainless steel 316 L pilot system with an open circuit to check the efficiency of a catalytic electrolyse towards this sort of biofilm. This process named Activ'H2O® was developed and patented by the Européenne Traitement des Eaux (ETE company) (Morales & Ginestet 2004). This process consists in a method of an electro-peroxidation eliminating the Pseudomonas aeruginosa-prone biofilm, thanks to hydrogen peroxide H2O2, a powerful oxidizer generated in situ by the system.

  • The stainless steel 316 L pilot system used in open circuit was used for experimentations linked to the carbogaseous treatment used in phlebology. The studies dealt with the safety, profitability and efficiency of this care.

  • The synoptic diagram (Figure 9) is a representation of this pilot system connected to the carbogaseous treatment unit that describes its constructive elements: a carbon dioxide bottle, a carbonator (equipment manufacturer: UNBESCHEIDEN) and a bathtub. The carbonator is set between the pilot and the bathtub in which the care is done; it is a stainless steel mixing column enabling the diffusion of the carbon dioxide gas into the natural mineral water of Dax.

Figure 9

Synoptic diagram of the carbogaseous care unit.

Figure 9

Synoptic diagram of the carbogaseous care unit.

CONCLUSION – PERSPECTIVES

The two pilots created by the Institut du Thermalisme are pioneering tools useful to make simulations and experimentations on systems on a semi-industrial scale on natural mineral water systems. Indeed the studies that were conducted so far essentially related to bacterial contamination controlled by physical or chemical disinfections.

Also, to complete spectrum experimentations, some alternative physical treatments like ultrasound and microwaves could be used in our prototypes to know their efficiency on a water system.

The next topics that shall be studied will relate not only on thermal spa systems issues, but also on balneotherapy and thalassotherapy centre water systems, and all health establishments.

It shall then be necessary to integrate the physico-chemical profile of the waters and the hydraulic parameters of the system to correlate all these parameters between themselves and propose relevant and technical solutions to the people in charge of these types of technical installations.

In addition to the sanitary hazard management of water systems, the sanitary hazard management in thermal spa pools represents a major application for the research activities linked to the stainless steel 316 L pilot. Hence, we bought an overflow pool bearing the technical characteristics compliant with the statutory regulations of surface pools exceeding 200 sq.m. (Arrêté du 7 avril 1981; Arrêté du 18 janvier 2002 modifiant l'arrêté du 7 avril 1981 modifié). This enables us to develop a different and absent topic in the bibliography dealing with the influence of pool water runoff (Figure 8) on the water microbiological quality in a pool with chlorine disinfection.

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