In Northern latitudes, active oxygen is a particularly popular alternative disinfectant to chlorine. Principally, however, for purposes of measurement what counts is whether the medium used contains persulfate or peroxide. Water disinfected with persulfate-containing media is measured according to the DPD N° 4 method. When using peroxide containing disinfection media, Hydrogen Peroxide tablets are used in connection with the Acidifying PT tablets. In both cases, the “Active Oxygen (O₂)“ designation is in fact misleading. It is not the molecular Oxygen that oxidizes (disinfects); rather it is an Oxygen radical which quite quickly combines with an additional radical to form molecular Oxygen (the air one breathes). This is also the main disadvantage to this method; because the disinfection effect does not last long and the effect is rather limited. As a strict rule, therefore, Chlorine is added in regular intervals when Active Oxygen is used for disinfection. Yet with the DPD N° 4 method false readings can then result (when simultaneously using both Chlorine and Active Oxygen), because the potassium iodide contained in this tablet catalytically splits the persulfates and thus the sum of persulfate and chlorine is indicated.

KS4,3 Acidity is also known as m-Alkalinity, Total Alkalinity, Hydrogen Carbonate Hardness, Acid Buffering Power, Temporary Hardness, … Alkalinity describes the ability of water to buffer the increase of ph value influencing chemicals (flocculants, disinfection media – e.g. chlorine products – lowering or raising pH). To provide a sufficient buffering effect, alkalinity should amount to at least 0.7 mol/m³ and/or mmol/l. This value represents the hydrogen carbonated materials dissolved in water. The buffering effect in the 4.2 – 8.2 pH range relies on a balance between hydrogen carbonate ions and carbon dioxide dissolved in water. Should chemicals that lower the pH value of water be added (acids), then the hydrogen carbonate ion combines with these to form carbonic acid (which in turn dissolves into carbon dioxide and water) and water. At a 4.3 pH value all hydrogen carbonate ions are depleted; thus the KS4,3 Acidity designation. Should in contrast chemicals be added that raise the pH value (bases), then hydrogen carbonate ions form again out of dissolved carbon dioxide and water. The modified relationship between dissolved carbon dioxide and hydrogen carbonate ions thus determines a new pH value. The buffering capacity of water becomes too low at alkalinities below 0.7 mmol/l, thus making it difficult to determine the pH value. In such cases small amounts of acids and bases will immediately and intensively change the pH value. Furthermore, water will have a corrosive effect on pipe mains. An alkalinity value which is too low can be increased through the addition of sodium hydrogen carbonate and/or sodium carbonate. When alkalinity values are high, however, the buffering effect is too large and large amounts of pH regulators are needed in order to achieve a change in pH. Additionally, when conditions are unfavorable (warming, pH > 8.2), calcium tends to precipitate because carbonate ions form out of hydrogen carbonate ions which in turn form water-insoluble compounds in the presence of calcium or magnesium (see Total Hardness). Alkalinity that is too high can be corrected through – at least partial – replacement of water. Because pH values above 8.2 will stop the equilibrium between hydrogen carbonate ions and carbonate ions, the alkalinity of the water must then (pH value over 8.2) be measured with the Alkalinity-P method.

Aluminum is a silvery-white, flexible alloy that is covered with an oxide layer in the air. Salt formation is made up of acids and bases, in this case mostly trivalent, and rarely monovalent. With approximately 8% in the earth’s crust, it is the most abundant metal and third most abundant element in the earth's crust. Aluminum is attained from bauxite, feldspar, mica, and clays. It is used technically as an alloying element for steels, bronzes, deoxidizers, paint, reflectors, and welding. Aluminum compounds are used as flocculants and as a flocculating agent in water treatment. Aluminum compounds are also used in medical products and cosmetics. The entry of aluminum into drinking water can be caused by insufficient flocculation, dissolution processes from soils, acid rain or wastewater, and from the aluminum processing industry. Aluminium is in groundwater concentrations at 0.01 - 0.10 mg/l. The average daily intake via drinking water is at 0.5 mg per day. Drinking water regulations limit: 0.200 mg/l.

Ammonium ion NH₄⁺ is a cation, which chemically reacts similarly to alkali metal ions, and forms salts of corresponding formula, such as ammonium nitrate (ammonium nitrate) NH₄NO₃ or ammonia (ammonium chloride). It is the conjugate acid-base for ammonia NH₃. It is not to be confused with quaternary ammonium compounds, in which nitrogen also has four binding partners, however, these are all organic residues and not hydrogen atoms. In the natural environment, however, ammonia results primarily in the degradation of proteins. It is excreted by fish and most other aquatic organisms as an end product, for example, via the gills. It is even released as an end product with the bacterial decay of dead biomass as an end product. It plays an important role in the citric acid cycle, in which it reacts with alpha-ketoglutarate to glutamic acid. Ammonium is, firstly to nitrite and other types of bacteria (Nitrobacter) to Nitrate, further oxidized and thus "detoxified" in the soil, and in areas under oxygen consumption from bacteria (Nitrosomonas). In addition to bacteria, archaea also play an important role in ammonium oxidation in soil. [3] This process is called nitrification and is thoroughly desirable in soil. Nitrification is also an important part of self-purification in water. Ammonia is toxic to fish even at low concentrations. Ammonium content in water of 0.5 to 1.0 mg/l, therefore, depending on the pH of the water, is regarded as questionable for fish life. Ammonium levels above 1 mg/l in waters are not suitable for fishing purposes.

The element boron is present in 0.001% of the earth's crust. In the natural environment, it is boron oxide, and in natural waters, mainly in the form of boric acid, H₃BO₃ or B(OH)₃. For plants, it is an existential element to stabilize membranes. Borates are used in glass production, and also as a flame retardant, and is also used in soaps, cosmetics, and detergents. Boron can, due to detergents, also be found via natural occurrences in drinking water. More than 0.3 mg/l of boron is rarely found in drinking water in public water supplies in Germany. In other countries (USA, UK, Chile), due to geogenic processes, significantly higher concentrations of boron can be expected. Commercially available natural mineral waters can contain much more boron than is found in drinking water. Drinking water regulations limit: 1.0 mg/l.

Using bromine as a disinfectant is becoming a popular alternative to chlorine. The advantage of this method is that combined bromine is unscented compared to combined chlorine (chloramine). That is, the disinfection effect is the same but human mucous membranes are not irritated. Disadvantages to the use of bromine products include, however, the limited oxidation effect and the higher prices and handling risks. Often a combination of bromine and chlorine is used, but this makes determining the concentration difficult. Under the DPD N° 1 method, measurements now show (if chlorine is used with bromine) the total concentration of free and total bromine and free chlorine. In order to establish the bromine concentration in this special case, the free chlorine must be converted into combined chlorine with the aid of DPD-glycine. In contrast to chlorine, the confirmation “DPD N° 1” reagent works with both free and combined bromine, thus always establishing the total bromine content.

The chemical oxygen demand, COD, as a summation parameter, is a measure of the sum of all oxidizing substances, under certain conditions, which are present in water. It indicates the amount of oxygen (in mg/l), which would be needed for its oxidation, if oxygen were the oxidant. The process is also known as "oxidizability Cr-VI" (chromate consumption if this would be the oxidizing agent), compared with potassium permanganate ("oxidizability Mn VII"). In addition to this use, as a measure of the concentration of chemically oxidizable substances in water, the chemical oxygen demand (as a measure of the chemically oxidizable substances in the production of a quantity of product into the wastewater discharged (g/kg of product quantity), or disposed of in a period (t/a, tons per year), is used.

Carbohydrazide, also known as hydrazine hydrate, is a chemical compound that is commonly used as a reducing agent in various industrial processes. It is also used as a reagent in the determination of certain metals and anions in water. Therefore, measuring the Carbohydrazide value of water can provide important information about the presence of certain metals and anions in the water, which can be used to assess the quality of the water and determine its suitability for various uses. In addition, the Carbohydrazide value of water can be used to monitor the effectiveness of water treatment processes and to ensure that the water meets certain quality standards. For example, if the Carbohydrazide value of water is too high, it may indicate the presence of harmful substances in the water, such as heavy metals, that need to be removed through treatment processes. Overall, measuring the Carbohydrazide value of water is important for assessing the quality of the water and ensuring that it is safe and suitable for various uses.

Chlorides are widely distributed throughout the natural environment, especially as sodium chloride (cooking salt), potassium chloride and calcium chloride. About 0.05% of the earth's crust contains chloride. A person consumes approximately 3 - 12 g Chloride (corresponding to 5 - 20 g NaCl) daily, with usual food. It is excreted through the kidneys and in sweat. Conventional water treatment processes do not reduce chloride concentrations. There is a need for a method of desalination (reverse osmosis, ion exchange, distillation). With the addition of hydrochloric acid or chloride-containing flocculants for pH correction, the chloride concentration is increased in the water. Levels above 250 mg/l can give the water a salty taste and concentrations above 500 mg/l are considered as unpleasant. Drinking water regulations limit: 250 mg/l.

Chlorine (in the form of sodium hypochlorite, calcium hypochlorite, chlorine gas, chlorinated isocyanurates, ...) has prevailed worldwide as the leading disinfectant for swimming and bathing pools. To measure chlorine concentration existing in water under DIN EN 7393, 3 partial values are to be distinguished. 1.) free chlorine: chlorine that is present as hypochlorous acid, hypochlorite ions, or dissolved, elementary, chlorine. 2.) combined chlorine: Portion of total chlorine which is present in the form of chloramines and all chlorinated derivatives of organic nitrogen compounds. 3.) total chlorine: Sum of the other two mentioned forms. While free chlorine immediately creates a disinfection effect, the disinfection potential of combined chlorine is highly limited. Chloramines are responsible for the smell of swimming pools and the irritation of human mucous membranes that lead to red-eye. A member of this class of substances is nitrogen chloride which humans already perceive at a concentration of 0.02 mg/l. Free chlorine is measured according to the DPD N° 1 method. Here N, N-diethyl-p-phenylenediamine (DPD), an indicator chemical, is oxidized by chlorine and discolors to red. The more intensive the discoloration, the more chlorine is present in the water. Photometric measurements or optical comparison with a colour scale allow the chlorine concentration to be measured. If a DPD N° 3 tablet is now added to this sample, then the combined chlorine will also be marked. The measured value now corresponds also to the total chlorine concentration. The concentration of combined chlorine corresponds to the difference between total chlorine and free chlorine. Since the slightest traces of the active chemicals in DPD N° 3 tablets lead to combined chlorine becoming active during the measurement, absolute care must be taken prior to the next DPD N° 1 measurement to sufficiently clean the measurement device thus avoiding false readings. The use of two differently calibrated vessels (one generally for measuring free chlorine and the other for measuring total chlorine values) is highly recommended.

Chlorine dioxide (2.33 times heavier than air) is known as a gaseous compound of the halogen, chlorine, and oxygen (ClO₂); which has the advantage over pure chlorine that it effects smell and taste perception less and that is also acts as an anti-virus. Chlorine dioxide is also manufactured at special facilities near the production site by combining chlorine gas and/or under-chlorinated acid and a fluid sodium chlorite solution (NaClO₂) (10:1). On average 0.05 mg/l – 0.20 mg/l are assumed as average minimum/maximum values.

Salts of chlorous acids HClO₂ are called chlorite. In the chlorite anion (ClO₂⁻) chlorine has an oxidation number of +3. In this state, chlorine and chlorite is a strong oxidant and easily decomposed. Chlorites are made by introducing chlorine dioxide (ClO₂) in sodium hydroxide -hydrogen peroxide solutions. The most important of these is sodium chlorite, a white crystalline salt. It is resistant in pure form and safely handled in solution. In a mixture with combustible materials, it is explosive. The sparingly soluble in water, light yellow colored chlorites of silver, and plump are explosive and may only be isolated under appropriate safeguards in pure form. They are used as bleaching agents for textiles. The ClO₂ (which is released during acidification) bleaches gentle fiber. In water, chlorite is formed during disinfection with chlorine dioxide. Chlorite builds up in water to chlorate from. Chlorite and chlorate have a toxicologically similar mode of action.

Chromium (from ancient Greek colour) is a chemical element with the atomic symbol Cr and atomic number 24. It is one of the transition metals in the periodic table in the 6 Sub-group (group 6) or chromium group. The compounds of chromium have many different colours, and are often used as pigments in inks and paints. Chromium in Water: Chromium occurs in nature, not in free form. The main chromium mineral is chromite. Chromium compounds are naturally present in small amounts in the aquatic environment. It can pass through a variety of industrial wastewater into surface waters. It is used as the finishing of metal surfaces or metal alloys. Stainless steel contains 12 - 15 % chromium. Chromium metal is produced worldwide in quantities of about 20.000 tons per year. It can be polished to a high shine and does not oxidize in the air. From the metal, the industry gets chrome mainly in the trivalent form in the water. Hexavalent chromium in industrial wastewater mainly originates from tanning and dyeing. Chromium compounds are used as pigments and for tanning leather. 90% of the leather is tanned by means of chromium compounds, wherein the wastewater usually contains about 5 mg/l chromium. They are also useful as catalysts in the impregnation of wood, in the manufacture of audio and (continued Chromium) video cassette and lasers. Chromite is the starting material for various refractory materials and chemicals. In the household waste Chromium may be from various synthetic materials. The isotope ⁵¹Cr is released during nuclear fission and can be used for medical diagnostic purposes.

Colour standards are defined according to the APHA (American Public Health Association) with the platinum cobalt (Pt/Co) scale. Another colour standard is similar to the Platinum Cobalt (Pt/Co) scale and is named after the chemist Allen Hazan Hazan as Hazan scale. Originally the standard was intended to describe the colour of wastewater, but the use is now extended to industrial applications in the chemical, pharmaceutical, beverage, plastics and oil industries. The colour scale goes from 0 - 500 units in mg/l platinum-cobalt to distilled water. The colour of the water is used as a measure of the concentration of the dissolved particles in the water. Thus, impurities – mainly by organic compounds – can be measured as colour.

There can be different reasons for measuring copper values. When it comes to drinking water, copper measurements are made in order to determine the quality of the drinking water. There are no official maximum permissible values for copper in drinking water, but there are recommended values of between 2 - 3 mg/l. Copper is a trace element and is thus essential to human life. Daily consumption of 0.05 – 0.5 mg/kg body weight is considered acceptable. Copper is, however, considered to be dangerous to organisms which is “positively” taken advantage of in swimming pool areas to combat algae and bacteria in the form of copper-containing algicides. However, copper-sulfate-containing algicides also have their disadvantages such as the possible discoloration of hair, spotting in swimming suits, and even corrosiveness and copper acetate sedimentation. As an example, copper releases into the drinking water from copper pipes. The “Copper/Zinc LR” tablet simultaneously measures both copper and zinc which is how zinc is eliminated from the reaction through the EDTA tablet included in the kit before both individual values are obtained. The “Dechlor” tablet prevents deviations in the measurement if the residual chlorine content is high.

Cyanides are the salts of hydrogen cyanide and are classified as highly toxic. They occur in the form of hydrogen cyanide, cyanide ions, complex-bound cyanides or organically bound. According to the German Standard Methods (DEV), a distinction is made between readily releasable cyanides and total cyanides. Thus, hydrocyanic acid and its alkali and alkaline earth salts belong to the easily releasable cyanides and are thus significantly more toxic than total cyanides, which include cyanocomplexes. Cyanide solutions are used in mining to extract silver and gold from rocks, but have been banned for this application in Europe since 2010. Cyanide salts are also important in metalworking, where they are used as hardening salts. Cyanocomplexes are harmless in terms of toxicity and are also used in the food industry, e.g. in the form of sodium ferrocyanide (E 535) and potassium ferrocyanide (E 538). However, research results indicate that photolytic cleavage and thus the formation of free cyanides can also occur with cyanocomplexes. The permissible exposure to cyanides is regulated in the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV). The test value for readily releasable cyanides in groundwater is 10 μg/l (ppb), that for total cyanides 50 μg/l.

When using organic chlorine products (trichlorisocyanuric acid and sodium dichlorisocyanurate), the so-called “isocyanuric acid” creates the carrier for chlorine. While the advantage of organic chlorine products clearly lies in the higher portion of active chlorine (up to 90%), the isocyanuric acid carrier substance can limit the speed at which the chlorine can kill off the bacteria when the concentration in water is high (>50 mg/l). It is thus recommended that one measure the cyanuric acid just as regularly as the chlorine content of the pool, in order not to counteract this fact by adding more chlorine (thus leading to higher isocyanuric acid being added).

DBNPA (2,2-dibromo-3-nitrilopropionamide) is a fast-working biocide which hydrolyzes, under both acidic and alkaline conditions. It is preferably used in water, firstly because there it is fast working, and in addition, degrades very quickly. TMA has a similar effect to halogen biocides. DBNPA is, among other things, used in papermaking as a preservative in paper coating composition, and in sludge.

Most aquatic organisms require a minimum concentration of oxygen, which is dissolved in low concentrations in the water. Oxygen can enter the water in various ways. On the one hand, it is released during photosynthesis by plants, algae and some bacteria. In addition, it is also absorbed directly from the atmosphere. The oxygen content of water depends on various factors such as temperature, pressure and salinity. For example, an increase in temperature can lead to a decrease in dissolved oxygen. The oxygen content depends on physical, chemical and biochemical factors and indicates the sum of all oxygen supplying and consuming processes. The dynamics of the oxygen content can only be determined by continuously recording measurement data. The higher the bioactivity of the system, the lower the oxygen content. In extreme cases, this can cause the water body to "die" as a result of excessive biodegradation of organic material.

The electrical conductivity is measured in the unit μS/cm and is a physical parameter in water analysis. Ultrapure water has a very low conductivity of approx. 0.05 μS/cm. Ions dissolved in water, such as chlorides, sulfates or carbonates, causes electrical current to be conducted. Thus, the level of conductance can give indications of impurities, water hardness or mineralization. Due to its high salt content, the conductivity of seawater is therefore 56.0 mS/cm. For humans, both too low and too high ion concentrations can be harmful, which is why the WHO has set an upper limit for electrical conductivity of 400 μS/cm. Reverse osmosis filters or activated carbon filters can be used to lower the conductivity value.

Erythorbic acid, also known as isoascorbic acid, is a chemical compound that is used as a food preservative and antioxidant. It is a naturally occurring form of vitamin C, and it is often added to processed foods to extend their shelf life and prevent the formation of harmful by-products, such as carcinogens. In terms of water quality, measuring the erythorbic acid value of water can provide important information about the presence of this compound in the water. This can be useful for a number of reasons. For example, if the erythorbic acid value of water is too high, it may indicate that the water has been contaminated by industrial or agricultural runoff, which can be harmful to human health. In addition, high levels of erythorbic acid in water can also affect the taste and odor of the water, making it unpleasant to drink. Overall, measuring the erythorbic acid value of water is important for assessing the quality of the water and ensuring that it is safe and suitable for various uses.

Fluorescein is a stable fluorescent tracer dye that emits green light with wavelengths between 520 and 530 nm upon exication with blue light with a maximum absorption at 495nm. It provides an accurate, cost effective method for monitoring industrial boiler applications when a fixed known amount is added to dosage program. Once added to the water circulation system it is stable over time and is environmentally safe when dosed at the concentrations required for boiler water analysis.

Fluoride is the monovalent anion (F⁻) of hydrogen fluoride. It occurs in the form of compounds which are predominantly found in rocks. The frequency in the earth’s crust is stated as 0.065 %, (weight). Salt content is found in drinking water via fluoride-bearing rocks. In Germany, there is an average, independent from ground water, of 0.1 mg/l to 0.18 mg/l. Fluoride levels were over 1.5 mg/l in only 0.3% of all drinking water samples. Geogenic and / or environmental causes in countries like India, Kenya, and South Africa have been elicited with fluoride concentrations above 25 mg/l. Fluoride is readily absorbed and deposited again by the body and of which up to 98% is located in the bones and teeth. Quantities of fluoride at 1 mg/l cause a caries prophylactic effect, however, daily amounts of 1.5 to 2 mg/l may already lead to dental fluorosis. This causes damage to the enamel and leads to osteosclerosis, a disease that can cause rigidity of the spine, thorax, and joints. Fluoride fluorination of drinking water in Germany is not being considered, due to the close co-existence of protective and also damaging effects. Apart from the possible failure of individual dental hygiene of consumers, fluorination of drinking water would result in a significant impact on the environment with fluoride, unable to be assessed otherwise as industrial emissions of this substance. Furthermore, fluorination is controversially discussed as “forced medication” via drinking water. Drinking water regulations limit: 1.5 mg/l.

Basically dissolved salts belonging to the alkaline earth elements calcium and magnesium are found in non-distilled water. In rare cases, strontium and barium can also be found. These combine with carbonate ions to form water-insoluble compounds (calcium). Through the total hardness measurement, the potential danger of calcium precipitation is measured as the required carbonate ions form from hydrogen carbonate ions when water heats up or when there are pH values that are greater than 8.2 (comp. Alkalinity). When measuring calcium hardness (SVZ1300 tablet process), only the part of the dissolved calcium in water is measured. The amount of magnesium dissolved in water is determined from the difference between the measurement and the total hardness.

Hydrazine is used for electricity generation in secondary electrochemical cells and alkaline fuel cells, primarily in aerospace, submarines (there is also an integral component of a rescue system used), and other military equipment. Diluted hydrazine solutions are used as reagents in the laboratory and for the deoxygenation (liberation of oxygen) of boiler feed water in steam power plants. It is used both for the removal of residual oxygen after the degassing of feed water, to protect against possible low oxygen breaks in the area of the capacitor, as well as for the catalytic removal of oxygen from the additional water. The advantage of using hydrazine is that only nitrogen and water are formed in this reaction. Besides deoxygenation, a rise in the pH value is also achieved in the water-steam circuit.

Carbohydrazide is a white crystalline solid with a melting point of 153 - 154 °C. at which point it decomposes. It is highly soluble in water, however, largely insoluble in organic solvents. Carbohydrazide is used to capture oxygen in the treatment of water for boilers. It is an alternative to the dangerous, and potentially carcinogenic, hydrazine. Carbohydrazide reacts with oxygen to produce water, nitrogen, and urea. Moreover, passivated metals and reduced metal oxides (iron oxide -> iron oxide; copper -> copper oxide). It is widely used in the manufacture of pharmaceuticals, herbicides, plant growth regulators, and dyes.

In Northern latitudes, active oxygen is a particularly popular alternative disinfectant to chlorine. Principally, however, for the purposes of measuring what counts is whether the medium used contains persulfate or peroxide. Water disinfected with persulfate-containing media is measured according to the DPD N° 4 method. When using peroxide-containing disinfection media, Hydrogen Peroxide tablets are used in connection with the Acidifying PT tablets. In both cases, the “Active Oxygen (O₂)“ designation is in fact misleading. It is not the molecular Oxygen that oxidizes (disinfects); rather it is an Oxygen radical that quite quickly combines with an additional radical to form molecular Oxygen (the air one breathes). This is also the main disadvantage to this method; because the disinfection effect does not last long and the effect is rather limited. As a strict rule, therefore, Chlorine is added in regular intervals when Active Oxygen is used for disinfection. Yet with the DPD N° 4 method false readings can then result (when simultaneously using both Chlorine and Active Oxygen), because the potassium iodide contained in this tablet catalytically splits the persulfates and thus the sum of persulfate and chlorine is indicated.

Iodine is a chemical element with the element symbol I, and the atomic number 53. It is in the 7th main group in the periodic table (17 groups), and thus belongs to the halogens. The name derives from the ancient Greek word "ioeides" for "violet color". When heated, the vapors released are characteristically purple. Tincture of iodine and iodo form contain iodine in an elemental or combined form, and are used as an antiseptic or antifungal agent. It is believed that the disinfecting effect is based on the elimination of oxygen from water. This oxygen is especially reactive shortly after its release, (in statu nascendi). Iodine is therefore used in certain cases for sterilizing water in swimming pools. It is advantageous in this context, since iodine is less aggressive than chlorine. However this water treatment cannot kill algae, so an additional algicide must be added. The intensive use of iodine can lead to skin discoloration. There is also, the risk of allergization. Both are avoidable with the use of so-called iodophors, carrier materials, which are capable of binding iodine.

Iron is normally attained via ferrous pipes into drinking water. Although these are often covered with a protective layer of zinc, which is designed to prevent corrosion (rust), the increases of iron in the water causes the gradual erosion of the zinc layer (see explanation on zinc). The limit for drinking water (in accordance with drinking water regulations->DWR) is 0.2 mg/l (= milligrams per litre, 1 milligram = 1 thousandth of a gram). The iron content limit fixed for DWR is meant, in this particular case, as a technical requirement for the protection against deposits in tanks and pipes. Iron content in drinking water is usually much lower than what is regarded for people as being the harmful limit of 200 mg. However a level of more than 0.2 mg/l can already cause unpleasant effects to occur because iron ions flocculate visibly upon contact with dissolved oxygen. Staining, turbidity, sediment, and a rusty and metallic taste, are consequences of this process. For these reasons, often even small amounts of iron are disturbing.

Isothiazolinones are heterocyclic organic compounds that are used primarily as biocides due to their bactericidal and fungicidal action. They are also used in the production of cleaning agents, paints, coatings and adhesives, and in paper manufacturing. Isothiazolinones have a cell-toxic effect and are classified as skin-sensitizing. They are therefore suspected of causing allergies. Isothiazolinones have therefore been banned in skin creams since 2017, while they may be used in wash-off cosmetics up to a limit of 15 mg/l.

Legionella is gram-negative, non-spore-forming bacteria from the Legionellaceae family. One subspecies, Legionella pneumophila, is mainly responsible for the infectious disease legionellosis in humans, which leads to pneumonia and can take a life-threatening course. The disease of legionellosis is mostly due to an increased concentration of legionella in drinking water, which can be caused by a lack of water circulation at temperatures between 25 °C and 50 °C. The disease can also be caused by a lack of water circulation at temperatures between 25 °C and 50 °C. These factors are met especially in large hot water tanks and pipelines. Legionella contamination in water is expressed in CFU (colony forming units). A value of up to 100 CFU/100 ml in drinking water is considered safe. If this measured value is exceeded, every operator is obliged to notify the public health department and to take action.

Magnesium is contained in sea water in an amount of about 1300 mg/l. In addition to sodium, it is therefore also the most abundant cation in the seas. In river water, the magnesium content is 4 ppm in seaweed at 6000 - 20000 mg/l and in marine fish and oysters at 1200 mg/l. Together with other alkaline earth ions, magnesium is responsible for water hardness (total hardness). Water with a high content of alkaline earth ions is called hard water and little alkaline earth ions as soft. Magnesium in water: Many minerals contain magnesium, such as dolomite (calcium magnesium carbonate; CaMg(CO₃)₂ and magnesite (magnesium carbonate; MgCO₃). The magnesium can be washed from the rock and rinsed in water. Magnesium can find many different uses and so on, for example, also production processes go into the water. In the chemical industry, it is added as a fire retardant or a filler, and other plastic materials. As a component of fertilizers and additive in animal feed, it gets very easily in the environment. Magnesium sulphate is used in beer brewing, and magnesium hydroxide as a flocculent in waste water treatment. Also, Magnesium acts as a mild laxative. Used as an alloy with other metals may be used for bodies of cars and aircraft.

Manganese is part of a variety of ores, and is present in 0.18% of the earth's crust. It frequently occurs in ferrous groundwater, although at lower concentrations than iron. In humans, for example, manganese is involved in the regulation of the carbohydrates and cholesterol metabolisms, and also plays a role in skeletal development. The recommended intake is about 2 - 3 mg per day (food intake, black tea). In water treatment, as well as iron, manganese is largely removed by oxidation and subsequent filtration. Eliminating microorganisms support the operations in the filter. Not sufficiently distanced manganese in drinking water can lead to a brown-black haze. Potassium permanganate is an approved, drinking water regulation, substance, for the oxidation and disinfection of piping. Small amounts of manganese causes deposits in the pipe network for long periods. When irrigation, pipe network, or operating changes (other flow conditions, flow direction reversal, switching to a remote water supply), these deposits can be picked up and lead to the already mentioned above opacities. There is also the risk of recontamination during deposition of organic matter with the manganese ("breeding ground"). Drinking water regulations limit: 0.050 mg/l Mn.

Methylethylketoxime, also known as 2-butanone oxime, is a chemical compound that is used as a solvent and reagent in various industrial processes. It is also used as a reagent in the determination of certain metals and anions in water. Therefore, measuring the methylethylketoxime value of water can provide important information about the presence of certain metals and anions in the water, which can be used to assess the quality of the water and determine its suitability for various uses. In addition, the methylethylketoxime value of water can be used to monitor the effectiveness of water treatment processes and to ensure that the water meets certain quality standards. For example, if the methylethylketoxime value of water is too high, it may indicate the presence of harmful substances in the water, such as heavy metals, that need to be removed through treatment processes.

Molybdate is a weak, oxidizing agent and is used as a corrosion inhibitor for pipes and vessels when heating and cooling water. It is, in usual concentrations, not harmful to aquatic organisms and bacteria and is also present in small amounts in drinking water.

The nickel content in seawater is about 0.5 - 2.0 μg/l, whereas rivers contain only about 0.3 μg/l of chromium. The nickel concentration in phytoplankton is 1 - 10 mg/l (dry mass), suggesting a bioconcentration factor of about 103 - 104 to seawater. Benthic algae that are found in both fresh and saltwater containing 0.2 - 84 mg/l, sea crabs from 0.14 - 60 mg/l, 0.1 - 850 mg/l molluscs and fish are 0.1 - 11.0 mg/l (all values on dry mass). Nickel occurs in water before especially as Ni²⁺ (aq) and possibly as NiCO₃. It can be dissolved or complexed with inorganic ligands present but also bound particulate form. Nickel occurs in nature, for example in front of slate, sandstone, clay minerals and basalt. However, the main source of nickel recovery is pentlandite. It is accumulated in sediments and is found in various biological cycles again. To diffuse nickel emissions from large combustion plants, waste incineration and metal industries. Nickel can also be introduced directly into the sewer line from various industries. It is used in the electroplating industry, the surface treatment of metals, alloys, nickel-cadmium batteries, as catalysts, and as a pigment. Pure nickel is often applied as a protective coating on steel and copper items. Nickel -copper alloys have been used for Coins for a long time. Other alloys are used for kitchen appliances, jewellery, etc... Nickel was found except in electroplating and as a mordant in textile printing and using nickel as a catalyst for fat hardening and the production of ceramic colours, just like nickel chloride. Nickel tetra carbonyl occurs as an intermediate in the purification of the nickel, and is used for various production processes. Nickel compounds are also found in agriculture. Traces of phosphate fertilizers and can be found on farmland near coal-and oil-burning industries. Organic substances have the tendency to absorb nickel even coal and oil contain a certain amount of this element. Nickel compounds are also found in sewage sludge, as well as in the slag and filter dust from waste incinerators.

Nitrates and nitrites are nutrients for plants, which have been used for many years as a fertilizer in agriculture, and also in small gardens, etc. nitrates and nitrites are convertible with one other, depending on the oxygen content in the water. The cause of health risks is the risk of a reduction of nitrate to nitrite. Such a conversion takes place in the intestines through certain bacteria. Secondly, the salivary glands can, via the blood vessels, reduce stranded nitrate. The current limit for NO₃⁻in drinking water is, according to German drinking water regulations, at 50 mg/l, and according to the Swiss Water Protection Regulations, at 25 mg/l, waters that exceed this limit are, often mixed with low-nitrate water in order to reach this limit. Recently, the first water treatment systems have been built using reverse osmosis or nanofiltration in order for the lower partial demineralization of the nitrate level in drinking water.

Nitrates and nitrites are nutrients for plants, which have been used for many years as a fertilizer in agriculture, and also in small gardens, etc. nitrates and nitrites are convertible with one other, depending on the oxygen content in the water. The cause of health risks is the risk of a reduction of nitrate to nitrite. Such a conversion takes place in the intestines through certain bacteria. Secondly, the salivary glands can, via the blood vessels, reduce stranded nitrate. The current limit for NO₃⁻in drinking water is, according to German drinking water regulations, at 50 mg/l, and according to the Swiss Water Protection Regulations, at 25 mg/l, waters that exceed this limit are, often mixed with low-nitrate water in order to reach this limit. Recently, the first water treatment systems have been built using reverse osmosis or nanofiltration in order for the lower partial demineralization of the nitrate level in drinking water.

Nitrogen is a chemical element with the atomic number 7. In molecular form, it is the main component of the air in our earth's atmosphere, accounting for 78 %. For nature, nitrogen in its oxidized form is of essential importance. Oxidation takes place through biological nitrogen fixation with the formation of ammonia and chemical nitrogen fixation with the formation of nitrogen oxides. Through nitrogen assimilation, plants and bacteria are then able to produce complex nitrogen-containing organic compounds, such as amino acids. Depending on the starting materials, a distinction is made between ammonium assimilation and nitrate assimilation. Nitrogen cannot be detected directly photometrically, but conclusions can be drawn about the concentration of oxidized nitrogen by measuring nitrate and ammonia.

The redox potential [V] is a parameter of chemical elements and compounds that quantifies the reduction or oxidation capacity. Reduction means uptake of electrons, oxidation means release of electrons. In a redox reaction, electrons are transferred from the reducing agent to the oxidizing agent, with one redox partner being oxidized and the other redox partner being reduced. The driving force for this reaction is called the electrochemical potential and is specific to each substance. In order to compare different redox pairs, the redox potential of each substance is defined with respect to the standard hydrogen electrode. The standard potentials (redox potentials) can then result in both negative and positive values and be classified accordingly in the so-called electrochemical voltage series. The more negative the redox potential of the analyte, the greater its tendency to donate electrons, i.e. to act as a reducing agent. In water analysis, ORP sensors (orp= oxidation-reduction potential) are used to measure the redox potential.

Oils are organic liquids that cannot be mixed with water and are characterized by their high viscosity. Depending on their chemical composition, a distinction is made between petroleum oils, mineral oils, fatty oils, vegetable oils and essential oils. Petroleum, for example, consists largely of alkanes, cycloalkanes and aromatics, while essential oils consist mainly of terpenes and sesquiterpenes. Through refining and extraction steps, oils can be separated into their components and thus purified for further processing. For this reason, oils are used in various areas such as plastics production, cosmetics, medicine or as fuels. Oils have a higher refractive index than water - they are therefore the optically denser medium.

Dissolved oxygen is one of the main causes of corrosion in boilers and steam circuits in power plants. The application of oxygen scavengers is one way to contain corrosion by chemically binding the oxygen. Oxygen scavengers include various compounds such as hydrazine, carbohydrazide and DEHA, which can react with molecular oxygen to form carbon dioxide, water, ammonia or molecular nitrogen. However, this can lead to the formation of copper-ammonia complexes, which is known as copper corrosion. Copper tubes are thus destroyed and also cause considerable damage. It is therefore important to ensure accurate dosing of oxygen binders by control measurement.

Ozone is comprised of 3 oxygen atoms (O₃). It is an unstable molecule and disintegrates, after a rather short time either in the air or when it is dissolved in water, into oxygen, O₂, and oxygen radical. The oxidative effect of this oxygen radical is very strong and a depot effect is ruled out because two radicals immediately combine to O₂. Ozone is produced directly on the spot by ozone producers and other required appliance-like devices. Special rules and precautions are required, because Ozone is 10 times more poisonous than chlorine. Thus Ozone is only used during a single dosage stretch – outside the pool – and must be filtered out before being used again (activated carbon). The maximum allowable concentration of ozone added to the pool is only 0.05 mg/l which is why ozone is insufficient as a disinfectant requiring it to be supplemented by other – as a rule chlorine content – disinfectants. Ozone kills bacteria, oxidizes organic contamination (e.g. urea), reduces chlorine usage, and leaves no irritating traces behind. As a rule, the human nose which can perceive ozone concentrations of 1:500.000 is the best measuring device. However, ozone combined with chlorine can be measured under the DPD method. By adding glycine, ozone is eliminated so that chlorine alone can be measured whereby the ozone content is determined from the difference.

Biguanide disinfectants are also gaining in popularity as an alternative to chlorine. Other than with other substitute materials, such as for example ozone or active oxygen, biguanides do not go well with chlorine, bromine, copper, or silver compounds. Nevertheless a counteracting agent is required because biguanides do not deploy an oxidative effect which is required, for example, for the breakdown of organic materials such as ureas and sweat. To do this, as a rule, hydrogen peroxide (H₂O₂) is used in addition to biguanide.

PTSA (1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt) is a stable fluorescent tracer dye that emits wavelengths between 400 and 500 nm when irradiated with UV light. It provides an excellent choice for the active on-line monitoring of cooling water treatment when a fixed known amount is added to the inhibitor being dosed. Once added to the water circulation system it is stable over time, doesn’t not react easily with other substances and is environmentally safe.

Peracetic acid (PES) is a highly reactive, highly toxic organic substance produced by oxidation of acetic acid. Due to this, peracetic acid is a strong oxidizing agent, which reacts explosively with air when heated above 110 °C, causing severe skin and eye irritation. It is used as a bleaching agent for papers, textiles and starch, and as a disinfectant and sterilizing agent. Commercially available concentrates are aqueous mixtures of PES, hydrogen peroxide and acetic acid and contain 5 - 30 % PES. For application they are usually diluted up to 0.3 % (3000 mg/l).

Permanganates are the salts with the anion MnO₄⁻. Due to their oxidative effect, they are used industrially for wastewater and exhaust air purification. Furthermore, they can serve as chemical catalysts, are widely used in synthesis, and as redox reagents in analytical chemistry. The latter allows accurate quantification by photometric and titrimetric methods.

Phenol is an aromatic organic compound containing a hydroxy group. Phenols are obtained mainly from coal tar. Phenols are, among others, also included in the plant, animal, and human body. Production and application: Phenol is a by-product coking plants. In industry, they are primarily in oil, in paints and varnishes, in foundries, in wood processing, can be found in the production of plastics and pesticides. Typical examples are nitro phenols, chlorophenols and PCP. Industrial use is the PCP, also in the paper industry and in pesticides. Chlorophenol is formed, for example, as an intermediate in the manufacture of medicines. Environmental impact and health: Phenol is considered to be atmospheric pollutant and carcinogen acts on the skin and the respiratory organs. The biodegradability of many phenols is very bad. PCP acts on microorganisms, plants, insects, molluscs and is very toxic to fish. Phenols must be mostly removed from the wastewater. Wastewater treatment/drinking water treatment: phenols can be found in large quantities in the effluents from coke ovens, gas works and charcoal plants, textile processing plants, refineries and the pharmaceutical industry. Due to its poor biodegradability other methods are usually preferred, depending on the composition of other waste water, such as oxidative process or membrane process.

Phosphates come up in nature in multiple ways, for example after it rains in the hills. But detergents also use phosphates as softeners. Phosphates are basically non-poisonous, even encourage the growth of aquatic plants and thus also algae, which are really not welcome in pools. When present in water, phosphates can be removed with “Phosphate Remover” products such as, the “Accepta 9079”.

Phosphonates are salts of the phosphonic acid and organic compounds. As salts exist primary (MH₂PO₃) and secondary (M₂H₂PO₃) phosphonates. The organic compounds of this group of materials (phosphorous) the formula R-PO(OH)₂ (R = alkyl radical or aryl radical) and differ from the esters of phosphoric acid by the direct bond of phosphorus with carbon (C-P bond). In contrast, phosphates are (similar to sulphates and sulfonic) COP bonds now, which can be hydrolysed much easier compared to CP bonds. In compounds of this type, the properties of a salt (or acid) are associated with the properties of the organic compound. So there are many compounds of this type that are soluble in water. Some technically important phosphonates carry amino groups in the manner of R₂N(CH₂)ₓ-PO(OH)₂ (R = alkyl or H). Some of these aminos have structural similarities with complexing agents such as EDTA, NTA or DTPA and have a similar function. They may include cations such as Ca²⁺ in the solution and alter the chemical behaviour of the cation. In the case of calcium, the property disappears to form water hardness. However, other cations can be bound in order to mitigate their chemical reactivity.

Phosphorus occurs in nature exclusively in bound form as phosphates and phosphonates. Phosphates occur as salts in the earth's crust in a proportion of 0.09 % and are of essential importance for living organisms. They occur as a component of bones, DNA or as adenosine triphosphate (ATP), which as an energy supplier makes life in the animal and plant world possible in the first place. Since phosphates are also an important nutrient for plants, they are used in large quantities as fertilizers in agriculture. Thus, overfertilization has become a problem for nearby water bodies. A high phosphate concentration leads to increased plant growth and thus to a reduction of the oxygen content. If the concentration of oxygen falls below a critical level of approx. 3.0 mg/l, fish die and the ecosystem is destroyed. The use of phosphate-containing detergents can lead to additional phosphate contamination of the drinking water.

Polyacrylates, polymers of esters of acrylic acid and of acrylic acid derivatives with alcohols are plastics which are used, among others, in coatings and adhesives, as a dispersant. Production and application: They are usually prepared by free radical polymerization, the uses of pure polyacrylic acid esters, however, are limited due to the low glass transition temperature. Polyacrylates are widely used in paints, coatings and adhesives and in the processing of paper and textiles. A well-known characteristic of the polyacrylates is the so -called polymethacrylate, better known as Plexiglas ®. Polyacrylates in water: polyacrylates are used as dispersants and calcium complexion in detergents and cleaners, and in water treatment.

Polyamines are a variety of chemical compounds that have both terminal and secondary amino groups in their chemical structure. Polyamines, such as HMD, are used in plastics production or as curing agents for epoxy resins. Other polyamines, such as spermidine and putrescine, belong to the biogenic polyamines and perform important functions related to cell division and growth.

Being the seventh most abundant element, potassium is represented by 2.6% of the earth's crust. In groundwater K⁺ ions are usually included in much smaller amounts than Na⁺-ions as potassium is an important nutrient for plants. The human need for potassium is about 2 - 3 g per day. The effects on water and pipe networks are not known for potassium.

Quaternary ammonium compounds are increasingly being used as a replacement of the previously established copper sulphate algaecide to eliminate their disadvantages (see copper). The use of algaecides is necessary despite correct use of chlorine or other disinfectants, to prevent the growth of algae.

Silica (often: silicon dioxide) is a collective term for the modifications of the oxides of silicon with the formula SiO₄⁴⁻. The bulk of sand deposits consists nonetheless of silica (quartz), not only because it is common, but also because of its hardness and chemical resistiveness, and in particular, its resistance to weathering. Silica is the major component of all the quartz glasses. The solubility of silica in water is strongly dependent on the modification or the temperature of the silica. The crystalline high-level quartz solubility is at 25 ° C at about 10 mg SiO₄⁴⁻ per liter of water. It should be remembered, however, that the solution equilibrium may adjust very slowly. The disordered amorphous silicic acids are significantly more soluble at the same temperature with 120 mg/l of water. [3] Some natural waters contain colloidal silicon dioxide (SiO₄⁴⁻), in addition to silica, which does not hydrate in water at normal temperatures into silica. The quantitatively most important, of which is in the form of silica, is glass. Usually it will improve with substances such as aluminum oxide, boron oxide, calcium and sodium oxide mixed, to lower the melting temperature, and to facilitate the processing or the properties of the final product. Pure silica is, difficult to melt, and therefore quartz glass is particularly resistant to temperature and temperature fluctuation.

Sodium hypochlorite (NaClO) is the sodium salt of hypochlorous acid. The intended use is bleaching or disinfecting (for example in swimming pools). Use in swimming pools is problematic, because the amount needs to be sufficient to chlorinate the ammonia present (or amines), in addition to the mono chloramine stage, since only then is a sufficient disinfection ensured. Sodium hypochlorite is also the main active ingredient of bleach and disinfectant household cleaners. Various mould cleaners or drain cleaners also contain this chemical. They are often advertised as “containing active chlorine". The application of sodium is found furthermore in dentistry. It is, for example used in root canal treatment to disinfect bacterially infected teeth.

Sulphates such as gypsum, anhydrite, etc. are widely found in the natural environment. Groundwater contains for this reason 10-30 mg/l sulphate. Sulphates are also components of chemical fertilizers, pesticides and detergents. Aluminum and iron sulfate are used in water treatment. Sulphate enters the water cycle via industrial waste water, for example from paper mills and textile factories. Sulphates are among the safest substances in water, but can the cause corrosion of water pipes. Waters containing large amounts of sulfate can be damaging to cement (sulphate flowering). A high sulfate content in conjunction with a high magnesium content such as tea and coffee leads to a deterioration of flavour. The maximum concentration is 250 mg /l of drinking water.

Sulphides are the salts of hydrogen sulphide H₂S, a very weak acid. Characteristic of sulphides is the smell of rotten eggs. Contact with acids (including carbon dioxide, CO₂, in the air), leads to the the toxic and flammable hydrogen sulphide being released. It reacts very strongly with oxidizing agents such as potassium permanganate or potassium dichromate. It is readily soluble in water, and the solution is strongly alkaline and very corrosive. Long-term storage of the substance leads to a slow reaction with water and a yellow color. Sulphides are used in tanneries as depilatories, in mining for ore flotation, in organic chemistry as a reducing agent, in wastewater treatment for heavy metal precipitation, and for the production of sulphur dyes. Furthermore, it is used to color glass, for the removal of NOₓ (nitrogen oxides) from exhaust gases, and for wood pulping. Sulphides enter wastewater in the form of sulphur compounds, in organic and inorganic forms, via industrial and commercial operations. Furthermore, they can also develop through the bacterial degradation of sulphur compounds in wastewater. Sulphide-containing waste water in an anaerobic, i.e. oxygen-free state, can produce so-called sulphide problems, from what was initially harmless wastewater. These include health and safety issues, difficulties in waste water treatment, odor, and the corrosion of building and other materials.

Sulphites are the salts and esters of sulphurous acid H₂SO₃. The salts contain Sulphite SO₃²⁻ as an anion. They are often used as a preservative in wine, dried fruit, and potato products. Sulphites occur naturally in almost all wines. Sulphite is not usually present in waters, as it is a good reducing agent and is easily oxidized into sulfate. The Sulphite concentration in boiler water and process water needs to be monitored regularly in order to avoid overdosing and the resulting damage to materials. Sulphite test kits use iodometric chemistry in which Sulphite is titrated with iodide-iodate. A starch solution serves as an indicator.

Total suspended solids (TSS) is a water quality parameter used for example to assess the quality of wastewater after treatment in a wastewater treatment plant. It is listed as a conventional pollutant in the U.S. Clean Water Act. This parameter was at one time called non-filterable residue (NFR), a term that refers to the identical measurement: the dry-weight of particles trapped by a filter, typically of a specified pore size. However, the term "non-filterable" suffered from an odd (for science) condition of usage: in some circles (Oceanography, for example) "filterable" meant the material retained on a filter, so non-filterable would be the water and particulates that passed through the filter. In other disciplines (Chemistry and Microbiology for examples) and dictionary definitions, "filterable" means just the opposite: the material passed by a filter, usually called "Total dissolved solids" or TDS. Thus in chemistry the non-filterable solids are the retained material called the residue. Although turbidity purports to measure approximately the same water quality property as TSS, the latter (filtering sample, weighting residue) is more useful because it provides an actual weight of the particulate material present in the sample. In water quality monitoring situations, a series of more labor-intensive TSS measurements will be paired with relatively quick and easy turbidity measurements to develop a site-specific correlation. TSS test on PrimeLab is a turbidity based measurement! Once satisfactorily established, the correlation can be used to estimate TSS from more frequently made turbidity measurements, saving time and effort. Because turbidity readings are somewhat dependent on particle size, shape, and color, this approach requires calculating a correlation equation for each location. Further, situations or conditions that tend to suspend larger particles through water motion (e.g., increase in a stream current or wave action) can produce higher values of TSS not necessarily accompanied by a corresponding increase in turbidity. This is because particles above a certain size (essentially anything larger than silt) are not measured by a bench turbidity meter (they settle out before the reading is taken), but contribute substantially to the TSS value.

The tannins (from the French tannin, also known as condensed proanthocyanidins) The main technical use of the tannins is in the production of leather (tanning), where they are used as tanning agents for cross-linking of the collagen molecules and thus to increase the durability and protection against micro-organisms. In the chemical industry tannins are used for the extraction of Gallic acid and pyrogallol. By condensation with suitable crosslinking agents (e.g., formaldehyde) to high molecular weight condensation products, binders can be used for bonding wood materials. As distinct antioxidants they are used as a dietary supplement and are also used for food preservation. They also have anti -viral and anti-bacterial properties. In medicine tannins used for its astringent effect as a haemostatic agent, as an antiseptic or treating excessive salivation (sialorrhoea). In folk medicine the expectorant effect is found in oak bark in Europe (for baths) and the bark of Acacia Verek in Africa.

Transmission is a physical measure to quantify the light transmission of a medium and thus plays a fundamental role in all spectroscopic methods. For photometry as a sub-discipline of spectroscopy, transmittance is of crucial importance, as the measurement method measures signal intensities and thus allows quantification of the analyte based on one or more measured wavelengths of a spectrum. The underlying concept of concentration-dependent light attenuation is described by Lambert-Beer's law.

Turbidity refers to the ability of water, to, sprinkle light on irradiated finely dispersed, suspended particles, and to reduce the transparency of the water. Raw water turbidity is caused by organic and inorganic particulates, and by living organisms. Turbity is therefore, often a measure or indication of impurities in the water. Turbity serves in water treatment monitoring, (eg fluctuating water quality), and optimization methods, (eg flocculation, filtration). Turbidity is quantified by measuring turbidity with the use of optical instruments. The measured values are indicated by units that relate to the calibration of formazine standard suspensions. In drinking water regulations, the Nephelometric Turbidity Units (NTU) are used. Drinking water regulations limit: 1.0 NTU.

Urea is an organic contaminant that is mainly introduced into the bath water through human excrements such as urine or sweat. The concentration increases with a high bathing volume or through heat. Urea itself is a crystalline and colourless compound which is completely soluble in water. In water, urea is decomposed by enzymes or bacteria present in the water to CO₂ and ammonium. However, the decomposition can also be oxidative. Although urea itself is odourless, so-called chloramines are formed during oxidation with a disinfectant such as chlorine, which are responsible for the characteristic chlorine odour and are also known as bound chlorine. Since active chlorine is consumed in the reaction, a subsequent dosage of the disinfectant may be necessary. Urea is therefore a good indicator of the degree of contamination of bathing water. The detection method is enzymatic, therefore the PL Urea 2 Reagent must be stored at 4 °C - 8 °C and the sample must be measured at 20 °C - 30 °C water temperature.

There can be different reasons for measuring copper values. When it comes to drinking water, copper measurements are made in order to determine the quality of the drinking water. There are no official maximum permissible values for copper in drinking water, but there are recommended values of between 2 to 3 mg/l. Copper is a trace element and is thus essential to human life. A daily consumption of 0.05 – 0.5 mg/kg body weight is considered acceptable. Copper is, however, considered to be dangerous to organisms which is “positively” taken advantage of in swimming pool areas to combat algae and bacteria in the form of copper-containing algicides. However, copper-sulfate containing algicides also have their disadvantages such as the possible discoloration of hair, spotting in swimming suits, and even corrosiveness and copper acetate sedimentation. As an example, copper releases into the drinking water from copper pipes. The “Copper/Zinc LR” tablet simultaneously measures both copper and zinc which is how zinc is eliminated from the reaction through the EDTA tablet included in the kit before both individual values are obtained. The “Dechlor” tablet that is also included in the kit prevents deviations in the measurement if the residual chlorine content is high.

The pH (potentia Hydrogenii) value is a measure of the strength of the acidic and/or base effect of a watery solution. It is particularly important when preparing bathing water because, among other things, it influences the effectiveness of disinfectants and the compatibility of the water with skin, eyes, and materials. A pH value of 5.5 is ideal for the skin. However, the water would then have so much acid that metallic materials would not only corrode but eyes would start to burn because tears have a pH value of between 7.0 and 7.5. therefore, a compromise must be found. In regard to materials compatibility, the pH value shouldn’t fall below 7.0 in any case. At the same time, pH values over 7.6 will have dermatological effects and will also influence the effectiveness of the disinfectant, thus negatively influencing the speed at with which bacteria can be killed off. Principally: At pH values above 7.5 = the natural coat of the skin that protects against acids begins to be destroyed (>8.0); in (medium) hard water, calcium precipitation beings (>8.0); the disinfecting effect of chlorine declines with (>7.5) pH values under 7.0 = chloramines form which irritate the mucous membranes and cause irritations to the sense of smell (<7.0); corrosion appearances in metal-content (installed) parts (<6.5); problems with flocculation (<6.2).