B: Article TROUBLESHOOTING AT A BATH WITH HYDROGEN
Contents
1. Depending on the results some tests have been dismissed because no new information was given The experiment strategy is based on evaluating the efficiency of the coagulation flocculation process as well as the effect of each parameter in this process For instance the test without coagulant is only done with high alkalinity level in order to demonstrate if there is still some active coagulant particle in pool water capable to form any flock with this alkalinity level as this experiment is not successful it is ruled out to do another one without coagulant addition In case of experiments realized with each coagulant the effect of alkalinity must be tested firstly with natural level 0 5 dH if it is not successful tests with high alkalinity level is done to compare with the real one All the experiments have been carried out with both reaction conditions in order to evaluate the pool flocculation system conditions in front of the supposed ideal ones Jar tests with different swimming pool waters have been done and no flocks have been observed Then it has been impossible to evaluate the effect of the kind of coagulant the alkalinity and the test conditions in the coagulation flocculation process However some small flocks and turbidity reductions about 70 have been obtained using lake water This result confirms the coagulants efficiency and obliged to take into account other possible causes those the experiment in the lab with pool water has no2. the filters at 45 60 m h in a back scavenging process With more pressure the water achieve to drag the wastes from the sand until the top of the filter where there is an outlet pipe In this process the water pass trough the filters many times before being removed and before the normal water filtration can work Sometimes back scavenging is made with a chlorine solution in order to remove the wastes better The disinfection system may be the last operation in the water treatment system It is made up of a low pressure Ultra Violet light chamber wavelength of light lt 300 nm in combination with the strong oxidiser hydrogen peroxide to generate very reactive radicals OH and then kill bacteria as quickly as possible according to the system water flow Thus the needed amount of hydrogen peroxide is injected depending on its concentration in the pool Tre Bjarnum Big Pool 80 T Botorm pool water water 20 inlets in be J o paom Coe a Balance Ma qm Oxa i i 17 H202 Nie HP mrte Fresh Lam i Filteri MOCHE A202 Water samples SAG t outlet outlet ing UV Chamber Strainer 3 y 1 _ Filter2 lt _ Q pump washing m i outlet 2 2 12 4 i r 4 H2504 pz Energy S 5 _ Filters sr AS t m Q 7 j am Be washing e 3 aler f control l gt PT washin 2 gt MIx pH non Filter4 filtrate J MIX Floc water n pipe Floculant fitrated pipe we b sa 04 filtrate
3. Combined Active Chlorine CAC presence in the water This kind of disinfectants forms some by products such as trihalomethanes which along with chlorammines can irritate eyes and respiration tracks and are also suspected carcinogenic Thus chlorine becomes dangerous for people who are exposed to these products for a long time for instance the professional swimmers or the pool attendants whose have been declared to suffer physical chronic problems as fatigue headache sore throat and eye irritations all of them probably caused by the work conditions Hydrogen peroxide is an alternative to chlorine disinfectants It has a high oxidation power and it does not produce problematic by products but it can build toxic compounds singlet oxygen and hydroxyls radicals Dieter 1988 cited in R Borgmann Strahse 2003 However its disinfectant efficiency has to be still demonstrated Hydrogen peroxide can enhance its disinfection properties in combination with other agents with metallic catalysts like Ag becomes a potent drinking water disinfectant R Pedahzur et Al 1997 with ozone or Ultra Violet light the oxidation power is enhanced from advanced oxidation processes Idil Arslan 2000 Besides in chlorine treated pools hydrogen peroxide can also remove chlorine by products like trihalomethanes and haloacetic acids those are formed when chlorine is oxidised by the air or condensated on process systems S Batterman 1999 From toxicological point of
4. Heater Figure 1 Bj rnum swimming pool water treatment system flow sheet Due to its mainly importance in this study Bj rnum flow sheet is represented Figure1 as an example of water system treatment However Bj rnum and Lund swimming pools have similar system treatment so similar flow sheet The main differences between these are that in Lund the treated flow is about 44 m h instead of 80 m h no Oxa H20 is added there are 5 filters instead of 4 and pH is regulated after filtration 2 2 Carried out tests 2 2 1 Filter test Filter tests are done full scale in Bj rnum system treatment In these tests hydrogen peroxide concentration and pressure are controlled before and after the filter Results are obtained in situ Hydrogen peroxide concentration is obtained in a spectrophotometer using water samples with a chemical Filter pressure values are taken in the filter pressure meter These tests are carried out twice the first when the normal water recirculating takes place and the second one after back scavenging In both tests water samples and pressure values are taken from each filter before and after the filtration took place 2 2 2 Jar test In this method a floculator machine is used in the lab It permits to mix the water regulating the stirring intensity in rpm and in two independent phases the coagulation or fast phase and the flocculation or slow phase In each two phases their stirring time is also selected as well as t
5. Hydrogen peroxide disinfectant swimming pool Jar test 1 INTRODUCTION Many people usually go to public swimming pools to do recreational activities They share a relatively small volume of water that has to maintain the sanitarian parameters stable all the time Because of that the pool water treatment system has to be efficient and friendly for the environment and human health as well Swimming pool water is usually polluted with different kinds of unwanted substances and microorganisms which are carried by the bathers There are many sources of contamination such as bacteria from skin and saliva pollution from swimwear cosmetics etc These microorganisms bacteria virus and protozoa can cause some illnesses like diarrhoea or several infections Is for these reasons that there is a high demand on disinfectants because they both achieve to kill the microorganisms and remove the dissolved pollutants via oxidation Almost all the swimming pools are treated with chlorine based disinfectants The most common chlorine based disinfectants is sodium hypochlorite that has been demonstrated effectiveness It kills bacteria by diffusion of hypohalous acid through the cell membrane White 1992 cited in R Borgmann Strahse 2003 and its disinfection rate depends on free available chlorine concentration type of organism contact time pH and temperature However high chlorine doses can provoke some hurts because of the Free Active Chlorine FAC and
6. and hydrogen peroxide consumption inside this Moreover sand filters were changed three weeks ago when its working live is about 10 year according to the suppliers Results of filter test during normal water circulation through the system treatment are shown in Figure 2 and 3 Dbefore filter Blafter filter Dbefore filter Bl after filter 120 18 110 1 4 100 1 2 1 2 1 2 i 90 m 2a 75 8279 S 80 _74 73 n 68 2 1 0 8 0 8 0 8 70 60 n x 06 50 o 40 A o4 30 0 2 20 0 10 4 3 2 1 0 4 3 2 1 filter i filter Figure 2 Manual pressure filter test Figure 3 Manual filter test during normal during normal circulation Bj rnum circulation to evaluate the hydrogen peroxide big pool 13 04 06 consumption Bj rnum big pool 13 04 06 In Bj rnum pool system treatment the pump usually works at 1 6 bar but due to pressure loss the water usually enters to the filters at 1 bar When the dirt goes increasing in the filters the pressure in the top enhances while in the bottom it decreases Pressure differences about 0 5 bar before and after the filtration means that back scavenging must be realized That is due to good flocculation or good dirt retention in the filter As is shown in Figure 2 pressure difference is lower than 0 5 in three to four filters so it could be because of a flocculation problem In Figure 3 hyd
7. coagulant come back to the pool becoming fats In swimming pool water the presence of suspended solids makes up an important contamination The size of this kind of particles can be really variable and many times visually imperceptible although they can cause the water turbidity The efficiency of Coagulation Flocculation process depends principally on the water characteristics the kind and dose of coagulant the reaction time the turbulence the pH the alkalinity the temperature and the equipment where the mentioned process is done During the Jar tests some of these parameters were changed to determine the effect of each one The water used in these Parameter analysed Value ee was collected from oH 640 jarnum pool surface Its physico chemical characteristics are shown Nitrat N 4 83 mg L in Table 3 Only using Dinofloc as Ammonium N 0 118 mg L a coagulant the water was from Ortho phosphate P 0 142 mg L Lund recirculation system to check Alkalinity 0 49 dH whereas the results were different COD 60 mg L According to Table 3 pH is lower Turbidity 0 1 NTU than the minimum required 6 8 ee Table 3 Bj rnum swimming pool water analysis results and it is able to affect negatively to coagulation efficiency The alkalinity value is also lower than the minimum recommended for the suppliers 5 dH COD represents theoretically the dissolved organic matter due to the insignificant turbidity value
8. it works as a good biocide Then fats can be formed because of coagulant that has not reacted with any colloid REFERENCES Renate Borgmann Strahsen Comparative assessment of different biocides in swimmng pool water Int Biodeterioration amp Biodegradation 51 2003 291 297 R Pedahzur H I Shuval and S Ulitzur Silver and Hydrogen peroxide as potential drinking water disinfectants their bactericidal effects and possible modes of action Wat Sci Tech Vol 35 No 11 12 pp 87 93 1997 Idil Arslan Isil Akmehmed Balcioglu Tuula Tuhkanen and Detlef Bahnemann H O UV C and Fe H O UV C _ versus TiO UV A Treatment for reactive dye wastewater Journal of Environmental Engineering 2000 903 S Batterman L Zhang and S Wang Quenching of chlorination disinfection by product formation in drinking water by hydrogen peroxide Wat Res Vol 34 No 5 pp 1652 1658 2000 ECETOC European Center of Ecotoxicology and Toxicology of Chemicals Special Report No 10 Hydrogen Peroxide OEL Criteria Document ECETOC Brussels 1996 Socialstyrelsen Bass ngbad SOSFS 2004 7 M Swedish swimming pool water requirements
9. view hydrogen peroxide can provoke skin eyes and respiratory track irritations in concentrations over 10 mg m of air ECETOC For swimming pool applications it is usually distributed at concentrations of 35 of aquous solution 1 1 Swedish swimming pool water requirements H FAC CAC Total chlorine COD Total bacterial Pseudomona P mg l mg l added mg l mg O l count cfu ml aeruginosa cfu ml lt 0 4 pH 7 2 6 8 7 8 lt 0 5 pH 7 4 lt 0 4 lt 2 lt 4 lt 100 lt 1 lt 0 6 pH 7 6 Table 1 Pool water requierements Socialstyrelsen SOSFS 2004 7 M 1 2 Review of Bj rnum pool situation In Bj rnum big pool the water flow to be treated come in 80 v v from pool surface and 20 v v from pool bottom Is in the water surface where some oil or fat can be seen The water from pool surface are manually analysed instead of pool water in recirculation system that are automatically analysed In this analyses pH temperature and hydrogen peroxide concentration are measured Three months of data are used to characterise how is the pool working related on pH and hydrogen peroxide measures The first problem is that the information given to automatical machine and manual tests are quite different According to the company manual test are much more reliable so the problem leads for the bad working of the automatical machine which has to be more often calibrated due to the mal functioning of the elect
10. B Article TROUBLESHOOTING AT A BATH WITH HYDROGEN PEROXIDE AS DISINFECTANT Victor Martinez i Vila e mail victormvila gmail com Abstract Typically swimming pools are disinfected with chlorine methods those have demonstrated their worth regarding killing of pathogenic micro organisms In Lund and Bj rnum pool hydrogen peroxide in combination with Ultra Violet light is used replacing chlorine It does not produce by products and is eco friendly However some problems like a fat development leading to increased costs and operational problems In the given study this cited swimming pools are descript Mostly Bj rnum pool is accurately characterised and evaluated according to data taken from the water system treatment which indicated some anomalies mainly in the filtration system To analyse that a full scale filter test was done it consist in water analysis and pressure meter reading after and before the filtration After back scavenging with fresh water the same filter test was done again to evaluate and compare it with the previous one The filter test results indicate a low cleaning power and hydrogen peroxide consumption inside the filters Because of that the hypothesis that diminute particles did not become flocks and came back to the pool took more force Therefore a flocculation Jar test was done Results with swimming pool water were not satisfactory so this hypothesis was ruled out because of no particles were present Keywords
11. CONCLUSIONS v Automatical H2O machine control has to be more often calibrated in Bj rnum pool to reduce the hydrogen peroxide consumption and so the costs y Automatical pH machine control has to be more often calibrated in Bj rnum pool to avoid getting values out the limits which are imposed by the water requirements or by some specification from some part of the pool water system treatment COD level in Bj rnum filters suffers an unusual enhance of 40 then this water comes back to the pool dirtier than when it is recirculated to the water treatment system v Pressure in Bj rnum filters does not increase as it should the mainly filters do not reach the pressure difference of 0 5 bar so the filtration efficiency is lower than the desirable v H O consumption increases when pressure difference is higher so more flocks organic matter or pollutants are inside the filters After back scavenging with fresh water the pressure difference disappears but H O consumption is maintained Y In flocculation Jar test performed no flocks was obtained so it was impossible to improve the flocculation process efficiency However the coagulants and Jar test efficiency was confirmed with lake water Y Pool water turbidity is so low about 0 1 NTU that permits to think that the COD in the water is due to dissolved organic matter which only can be removed by the oxidant in this case H20 that according to external bacterioligical analysis presented
12. a main characteristic that hydrogen peroxide along with Ultra Violet light is used as disinfectant All of these have a recirculation system where the first stage is a balance tank to maintain the desirable level on the pool and control the flows through the pipes filters and Ultra Violet chamber After the balance tank the pool water pass through a strainer removing big particles like hair and lint to be pumped to the filters Both before and after the filtration automatic measure machines can control the system in continuous it usually controls both pH temperature disinfectant concentration on the pool water flow and the amount of chemicals available in the can to provide the daily consume After that the water flow is pumped to the filters but before it enters there a certain amount of coagulant is added normally about 0 4 l l The filtration process is made up of four or five filters in parallel Each filter has one pipe inlet one pipe outlet and one pipe that can work as an inlet or outlet in order to be able to do the pool water filtration and the filter back scavenging In the filtration system the pool water enters into the filter about 2 3 m s on the top of it percolling through the filter at 15 20 m h in contact to three kinds of sand or gravel where the particle diameters are from 0 4 to 5 millimeters then the cleaner water go out to the back of the filter to be disinfected When the filters have to be cleaned the fresh water cross
13. e coagulant phase with the highest floculator turbulence 400 rpm during 15 seconds followed by a short slow phase of 1 minute to 50 rpm The second one tries to reproduce the ideal flocculation according to the found literature adding the coagulant with a high turbulence 200 rpm during 3 minutes in the coagulant phase followed by the flocculant phase where reducing the stirring intensity to 50 rpm during 7 minutes the particles join together and form aggregates After that wait about 20 minutes to let flock precipitation The results are obtained firstly showing the amounts of precipitate If some precipitate has been obtained turbidity measures can be done to evaluate quantitatively the coagulation floculation reaction Finally in case to obtain good turbidity results COD measures can be carried out to evaluate the organic mater removal due to suspended solids 2 3 Analysis Samples for analysis were taken from different kinds of water pool water recirculating pool water and water from experiments carried out in the laboratory Nitrate was determined using the Dr Lange method LCK 339 Ammonium using the Dr Lange method LCK 303 Phosphate using the Dr Lange method LCK 349 and COD concentration using the Dr Lange method LCK 114 Alkalinity was determined through SS EN ISO 9963 1 pH was determined with an hydrogen selective electrode and turbidity using a turbidimeter 3 RESULTS AND DISCUSSION 3 1 Filter tests Filters tests have bee
14. he sedimentation time Another matherials and products used in Jar test are pool water three kinds of coaguland micropipette available range from 0 5 to 10 microliters pH meter thermometer sodium carbonate and hydrochloric acid 0 1 M At the beginning of the test 1000 ml of pool water is put in a baker this water is collected from the Bj rnum pool or from the Lund recirculation system Then the baker is immersed in a water bath to reach 25 C The desirable alkalinity is adjusted with sodium carbonate three alkalinity levels are tested the natural pool water alkalinity 0 5 dH 5 dH and 10 dH After that the pH has to be adjusted with hydrochloric acid solution to reach a pH range of 6 8 7 8 optimal for the coagulation and inside Swedish water requirements Subsequently the flocculator is turned on with the desirable condition test and 0 5 microliters of one of three coagulants is added This coagulants are polyaluminium chloride Sachtoclar and Dinofloc and sodium aluminate Optofloc all of these used by International Marketing AB in Lund and Bj rnum Each of these solutions are tested in two different conditions varying the turbulence and reaction time in each phase The first condition tries to simulate the real situation in the pool water system treatment although it is impossible because the turbulence in the first section of the pipe is twice than the flocculator capacity 400 rpm Therefore the coagulant is added in th
15. n done in Bj rnum pool system treatment in order to evaluate how they work and thus find a technically feasible way of solving the problem Firstly some water parameters taken before and after the filtration system are analysed in the lab as it is shown in Table 2 In Table 2 the strange filter functioning Parameter can be deduced Although nitrogen based analysed Sample 1 Sample 2 compounds and phosphorous i 67 66 concentration values do not follow a bad wee BF progress in the filtration pH value are too Nitrat N 1 01 mg L 1 01 mg L low and COD suffers an unusual enhance Ammonium N 1 34mg L 1 38 mg L7 COD increases its value in 40 in the filter therefore the water comes back to Phosphate P 0 15 mg L 0 12 mg L the pool dirtier than when it is Alkalinity 0 5 dH 0 5 dH recirculated to the water treatment COD 53 mg L 74 mg L system It seems clear that something does not work well in the filtration Turbidity 0 1 NTU 0 1 NTU system it could be because of a Table 2 Bj rnum water filter test 08 03 06 flocculant or disinfectant problem Is for Sample 1 is from water taken before the filter and this reason that a full scale filter test have Sample 2 is from water taken after the filter been done Water Temperature 16 C In these filter tests hydrogen peroxide concentration and filter pressure was specially controlled both before and after the filter in order to evaluate the flocculation
16. rode might be caused for the fats Moreover it is also a problem that the hydrogen peroxide consumption depends on the automatically measurements and it does not work as a proportional control system which tries to avoid the peaks so far to the set point which is in 88 ppm Therefore the hydrogen peroxide consumption varies dramatically which represent an important costs increases as well as the possibility to achieve stabilize the hydrogen peroxide pool concentration and so to optimize the disinfectant efficiency Approximately once a week back scavenging with fresh water is made and once a month back washing filter with chlorine is made too when that occur the amounts of fresh water increase However the effects of these on the system cannot be evaluated with the data taken although it seems that back scavenging and chlorination help to maintain the system more stable Bacterial analyses done every 15 days during these 3 months of data demonstrate that the pool water is correctly disinfected Total bacterial count concentrations are about 10 cfu ml much lower than the limit 100 cfu ml Pseudomonas Aeruginosa s concentrations are also given and its concentration is on the correct value which has to be below 1 cfu 100 ml of water 2 MATERIAL AND METHODS 2 1 Swimming pool water system treatment The swimming pools that has been experimented and evaluated are Skane pools provided by International Marketing Sweden AB Those have as
17. rogen peroxide consumption is shown This consumption is only significant in filter number 3 the same one that presented pressure difference of 0 5 and the huge amounts of dirt inside Therefore that could mean that the hydrogen peroxide with its hydroxyl ions were consumed by the coagulants or by the organic matter After back scavenging the pressure is 0 9 bar in all the filters and also before and after each filter it means that the filter is cleaned correctly In this filter test hydrogen peroxide concentration is a little bit higher However hydrogen peroxide consumption is similar than before back scavenging maybe because it more difficult to remove some pollutants if they are mixed with the sand or dissolved in water Another possibility of hydrogen peroxide consumption is due to the reaction with coagulation chemicals that are positively charged As is shown in Table 2 the recirculating water suffers a COD enhance when it cross the filters but the turbidity is always very low about 0 1 Therefore COD can be due to the dissolved organic matter and its enhance because of the contact with the dirtiness into the filter which could provoke an increase of hydrogen peroxide consumption 3 2 Flocculation tests Flocculation tests are performed through Jar test method to check and improve the coagulation flocculation efficiency as well as to confirm the hypothesis that reaching bigger flocks is possible to avoid that small colloids mixed with
18. t work as it was expected Maybe it is really difficult to obtain some flocks with water of very low turbidity 0 1 NTU and also with a laboratory equipment that do not permit to reproduce the coagulation flocculation process of the pool system treatment About that note that the turbulence is much higher in the pool system treatment than in the lab equipment so the small coagulant doses added in the water can be put in contact much easier with the pollutants that theoretically exist increasing its efficiency However the reaction time in the pool system is very short and could be insufficient to the good flocks formation Besides the scale problem has to be considered because to obtain flocks from 1 liter of relatively clean water can be difficult when too much flocks are not obtained in the filters after 7400000 liters of pool water with coagulant pass through them every week note that Back Scavenging is done approximately every week Thus with turbidities about 0 1 NTU it is easy to think that the COD in the water is due to dissolved organic matter which only can be removed by the disinfectant in this case hydrogen peroxide However according to the bacterial analysis hydrogen peroxide in combination with UV light is a good biocide Thus it would not be a good idea to rule out the possibility that fats can be diminute flocks coagulant pollutant blend or just coagulant that can cross through the filters coming back to the pool 4
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