Our maintenance team are care for the :PH levels, BOD, COD and total dissolved soiled of the water before and after our system are also checked ones a month to ensure that the treated water parameters are regulated to the safest levels according to international and national safety standards.
Biochemical Oxygen Demand – BOD
Biochemical oxygen demand or BOD is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. It is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. It is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days (BOD5) of incubation at 20°C and is often used as a robust surrogate of the degree of organic pollution of water.
Chemical Oxygen Demand
Chemical oxygen demand (COD) relies on chemical oxidation with chromic acid (a strong oxidizer). Many organic compounds, including color bodies and fibres, which are not easily biodegradable, along with any inorganic chemicals will show up as chemical oxygen demand but not biochemical oxygen demand (BOD). Some mills have found that filtered COD samples give a better surrogate for the five-day BOD test than the one-day BOD test. Chemical oxygen demand (COD) is the amount of a specified oxidant that reacts with the sample under controlled conditions. Results are defined as the mg of Oa‚‚ consumed per litre of sample. The sample is heated for two hours with a strong oxidizing agent, potassium dichromate. Oxidizable organic compounds react reducing the dichromate ion to the green chromic ion. The amount of Craºa¶ or Craº ³ is measured calorimetrically with a spectrophotometer. Chemical oxygen demand can be used to estimate biochemical oxygen demand (BODa‰ˆ ½ COD) and determine the dilutions needed for the BOD five-day test. Total COD is run on undiluted samples. For a soluble COD, the samples are filtered through a 0.45 mm filter before analysis to remove biological interference. 2 mL of the sample is pipette into a COD digestion reagent vial. The vial is then inverted several times to mix (vial will get hot). The vial is placed in the COD reactor at 150 ° C for two hours. The samples then cool and the samples are tested using a spectrophotometer. The chemical oxygen demand value will be read in mg/L for both total COD (tCOD) and soluble COD (sCOD).
For samples with a concentration of 0 to 150 mg/L, use the low range COD vials. For higher concentrations the high range COD vials (0-1500 mg/L) should be used. If the COD exceeds 1500 mg/L, the sample should be diluted to bring the results in range. Chloride is the primary interference. Vials with mercuric sulphate can be used to eliminate chloride interference up to 2000 mg/L Cl–. Samples with higher chloride concentrations should be diluted enough to reduce the chloride concentration below this limit. If the sample is diluted the values are adjusted based on the dilution factor. If the COD testing is for permit reporting, the method including vials with mercury is the EPA approved method.
Chemical Factors – pH
PH is the term used to refer to the degree of activity of an acid or base in the water and is the important chemical factor. PH is measured on a scale from 0 to 14 with 7 being neutral. A pH value between 0 and 7 is considered acidic with 0 being the greatest acid activity and getting weaker as it approaches a value of 7. A value of 7 to 14 is considered basic with 14 being the greatest base activity. Gray water pH is best kept in the range of 7.0 to 12.0. When pH remains below 7.0, the water is considered to be corrosive. This means etching of plaster and metals in equipment such as heat exchangers will result. In addition, it is more difficult to keep chlorine in the pool because while more effective as a sanitizer at the low pH, chlorine is also much less stable resulting in the consumption of larger quantities of chlorine than would be used at normal pH levels.
Maintaining the pH higher than 12.0 will increase the tendency to form scale or cloudy water. Calcium, the major component in scale, is a relatively unstable mineral and when the pH is high, the calcium is not as soluble and it will have a greater tendency to precipitate or “fall out” of solution resulting in cloudiness or scale. High pH will also reduce chlorine effectiveness resulting in the need to maintain higher chlorine levels to achieve maximum sanitization. If the pH is low, sodium carbonate, otherwise known as pH up or soda ash, is added to raise the pH. If the pH is high, pH Down is used. PH Down comes in two forms: liquid acid (muriatic acid) or dry acid (sodium bisulphate).
Total dissolved solids
Total dissolved solids (TDS) are normally the least worrisome factor.TDS is the sum of all materials dissolved in the water and normally runs in the range of 250 ppm and higher. There is much discussion over what levels are considered too high, but there is no real lower limit. TDS is comprised of many different chemical compounds, which means that the issue of how much is too much actually depends more on what they consist of than how much there is. For example, sodium chloride or ordinary salt is extremely soluble and is therefore unlikely to cause a problem, whereas, as we have seen, calcium compounds can be a problem even at fairly low levels. In general, when the TDS exceeds approximately 1500 ppm, problems may begin to occur. It must be pointed out that pools whose sanitizing systems are based on chlorine or bromine generation equipment (salt generators) will likely have much higher TDS levels.
These pools actually have salt in one form or another added to the pool. The salt used is highly soluble and does not cause the type of problems normally associated with high TDS, but never the less, it does add to the TDS level in the pool. When testing water in this type of pool for TDS, the salt intentionally added to the pool needs be taken into account. At elevated levels, TDS can lead to cloudy or hazy water, difficulty in maintaining water balance, reduction in sanitizer activity and foaming. Unfortunately, the only way to reduce TDS is to drain a portion of the water and replace it with fresh water. Sequestering agents do not help when high TDS levels are causing cloudy water.
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