The Refurbishment of Filtration & Chemicalisation Systems On A Recent Project Paper Prepared By:- Mr McDermott Swimming Pool Filtration Ltd, 3 Wellside Drive, Cambuslang, Glasgow G72 8TA
In Brief The filtration and chemicalisation systems were totally refurbished 9 years ago. At that time the site had a 33 metre pool which, during the refurbishment, was shortened to 25 metres to accommodate a new leisure pool and flume. The site has retained its existing teaching pool. Problems 1) Whilst planning the refurbishment in 1995, it was decided to install only 2 filtration systems. One filtration system for the 25 metre pool and one for the leisure pool, flume and teaching pool. The concept behind this idea of connecting 2 or more pools to one filtration system is, to an experienced filtration engineer, incomprehensible. Local Authorities should understand that there is only one way to maintain the correct filtration of swimming pool water, the correct way, irrespective of economics.. Each pool should have its own filtration system, if this is unaffordable, the site should not consider housing extra pools. 2) A lack of foresight at the initial designing phase meant that there had been no access allowed for the removal of the existing 3 x 2.5 meter steel filters, or for the installation of similar sized replacement filters. 3) Due to the lack of access, banks of small filters were installed at the site on both of the systems. With less filtration than the original plant and the addition of the new leisure pool and flume, problems were inevitable. When installing banks of filters, extra care must be taken when calculating the pipework hydraulics, to ensure that each filter is receiving the correct flow of water and that each filter should, ideally, have it s own flow meter. The most essential part, when installing any filtration system, is to ensure that filters are sitting level, on a level plinth. If the filters are not level then the filtration system will have a built-in problem from day one. 4) During the past nine years, there has been a variety of problems, not least the splitting of the filters on numerous occasions. This has resulted in the flooding of the plantroom as well as pool water problems. 5) The chemical treatment on all swimming pools can be a potential problem. How do you keep the pool chemically balanced when, two buses full of children all decide to enter the pool? When you have gismos fitted, ones which require you take water to them, then you have a lag time (pool turnover) it is at this point that the water can be unbalanced. 1 Gismos n. gadget, gimmick Source: The Concise Oxford Dictionary ~ Seventh Edition
6) The other issue we had to rectify was that of the mains water feeding the swimming pools, (last year there was a report of Cryptosporidium in the mains water). 7) The teaching pool, leisure pool and flume had previously connected to the one balance tank and one filtration system, resulting in both pools having to be closed when unwanted contamination entered the pools. 8) The leisure pool features have their own separate pipework and circulating pumps as the water in the pipework will be stagnant when the features are not in use, therefore creating chemical and microbiological problems, when they are switched back on. 9) The balance tank for the leisure pool has the return pipework to the leisure pool running through it Swimming pools that do not use the correct equipment are inevitably, a potential danger to public health.
Solutions Page 42 of The Treatment & Quality of Swimming Pool Water D.O.E. 1984 stated:- Where an establishment contains two or more pools, each should have separate sets of circulating pumps and filters for normal use. 1) The new filtration and chemicalisation systems have been designed to comply with the German DIN Standards, and more. We completed this installation in January 2004. 2) Our main objective at the start of this project was to find a reputable filter manufacturer who would be able to supply 2.5 metre diameter by 3 metre high filters. These filters would have to be able to fit through an opening of 3 metres by 1 metre. Our specifications for the filters to comply with the German DIN Standards were; (i) (ii) (iii) (iv) (v) (vi) (vii) 2.5 metres x 3 metres cut into three sections nozzle plate outlets with 12 (300mm) inlet and 12 outlets easy access manhole to bottom of nozzle plate side entry manhole top entry manhole a viewing window on the side of the filter We did find a reputable filter manufacturer that could not only comply with our specifications but could also improve upon it by fitting a patented inlet diffuser which would ensure the filter media bed would be level. They could also supply a light on the inside of the filter vessel, and yes, they are a German based company! 3) We wanted to install two filters for the 25mtr pool so that we could establish a flow rate of 12.5m³/m²/hr, with a backwash rate of 40m³/m²/hr. Also we installed one filter for the leisure pool plus flume, giving a flow rate of 10m³/m²/hr with a backwash rate of 40m³/m²/hr. We also installed another filter for the teaching pool to give a flow rate of 10m³/m²/hr with a backwash rate of 40m³/m²/hr. 4) Our rationale for installing quality filters with the 12" backwash pipework was to ensure that there would be no backpressure on the filter when the filter media bed is lifted up by 100mm during a backwash. This would ensure removal of all dirt. If backpressure is present, then all the dirt would not be removed. The DIN Standards require that a backwash can be carried out with the top manhole cover removed, to prove there is no backpressure. Under no circumstances should the backwash pipework run above the filter. All commercial installations should use air and water during the backwash.
Solutions (Cont.) 5) Good quality flow meters, monitoring equipment (amperometric), valves and mains water meter have to be fitted. Proper medium flow rates 10mtr to 15mtr³ must be adhered to, anything other than this would be false economics. Our statement German DIN Standards and more ~ the more being the new filter media which we are using and have been using for the past 6 years, Activated Amorphous Silica, (trade name A.F.M.). This is a recycled glass that may have the same life span as that of the filter. Its properties far outweigh silica sand and can help prevent turning the filter into a bio-filter ~ this is extremely important. We are also using two coagulants, therefore we can achieve after the filter, 0.5 micron. Thus ensuring the pool has crystal clear water. Therefore we installed another chemical product which when added to the water will provide a bank, in all of the water, therefore keeping the water balanced all the time, (trade name, the Wapotec System). The other chemicals being used are Calcium Hypochlorite, P.A.C., Sodium Bicarbonate, CO 2 and Calcium Chloride Flake. 6) Therefore we installed a 1 micron filter to the incoming mains water for the entire leisure centre and also separate activated carbon filters on the mains water feeding the swimming pools. This ensures that should there ever be another report of Cryptosporidium in the mains water; the leisure centre should be able to remain open. 7) We redesigned the pipework, arrangement of valves and supplied each pool with it s own totally separate filtration system. 8) We decided that in order to keep the features pipework on the leisure pool chlorinated, we would introduce a 1" pipe from the filtration return after the chlorine injection point. This continually runs into the features pipework adding chlorine. 9) To keep the balance tank chlorinated; we fitted 2 saddles on the return pipework with 2 ½" pipes continually running into the balance tank. Swimming pools that do not follow the above will usually experience some problems, whether they are chemical problems or of poor water quality. No matter how many electronic gismos 1 are fitted, there will still be problems, in addition to the extra problems expensive gismos create. 1 Gismos n. gadget, gimmick Source: The Concise Oxford Dictionary ~ Seventh Edition
Chemical Parameters! Free chlorine, as low as possible to ensure that the pool water is bacteria free, usually 0.6mg/l! Combined chlorine, no more than 50% of the free chlorine! ph 7 to 7.4! Calcium hardness min. 200mg/l! Alkalinity min. 50mg/l! T.D.S. no more than 1,000mg/l above the incoming mains water.! THMs as low as possible (F.I.N.A. Standard below 20ppb).! Combined chlorine are we getting the correct readings using the DPD No. 3 test tablets? We know that there are chemicals that do interfere with the readings, from the tablets. This tablet was designed some 50 years ago, but the amount and type of chemicals being introduced to the pool water by the bathers can change at an alarming rate, i.e. old, new and up-dated products such as suntan lotions, moisturizers, hair conditioner, deodorants, etc.! From analytical work completed we are satisfied that the combined chlorine measured present NO public health risk.