Every day, the drinking water plant’s water treatment equipment converts raw water into qualified drinking water. These indicators reflect both the quality of raw water and the quality of finished water. As a water treatment production company, we must also conduct water treatment production using water indicators. In our many years of experience, we have frequently encountered the following questions from our customers:
- What are the indicators in the water?
- What does each indicator mean?
- What is the impact on the human body or device?
Microbial indicators, toxicological indicators, sensory traits, general chemical indicators, and radioactivity indicators are the four types of common drinking water indicators. Toxicological indicators are important indicators for assessing water quality. Because general water treatment methods such as filtration, sedimentation, and coagulation do not always completely remove them. Toxicological indicators must be considered when choosing water sources.
The following are the current common indicators and drinking water limit values in China. Linho explained and described the health effects of each indicator. I believe you can gain a better understanding of the indicators by using this table. It will also assist you in selecting a more appropriate water treatment.
| NO. | Indicator | Limit Value | Indicator Interpretation | Health Effects | ||||||||
| A. Microbial Indicators | ||||||||||||
| 1 | Total Coliform Flora | Should not be checked out (MPN/100ml or CFU/100ml） | A group of aerobic and facultative anaerobic bacteria, which can ferment lactose when grown at 37 °C, and produce acid and gas within 24 hours. They are gram-negative Bacillus without bacillus. | Indicates that water, soil, dairy, or refreshing beverages have been contaminated directly or indirectly by human or animal feces. | ||||||||
| 2 | Escherichia Coli | Should not be checked out (MPN/100ml or CFU/100ml） | Normal hermit bacteria in the intestines of animals. A small part of them cause disease under certain conditions . | Under certain conditions, E. coli can cause gastrointestinal infections in humans and a variety of animals, as well as local tissue and organ infections such as the urethra. | ||||||||
| 3 | Total Number Of Colonies | 100 (MPN/100ml or CFU/100ml） | Colonies are growths that formed by bacteria’s growing and multiplying on solid medium. They can be recognized by the naked eye. They are composed of tens of thousands of identical microorganisms. | Consumers who consume foods high in microorganisms are at risk of developing intestinal diseases such as dysentery, which can cause vomiting, diarrhea, and other symptoms, putting their health and safety at risk. | ||||||||
| B. Toxicological Indicators | ||||||||||||
| 4 | Arsenic | 0.01 mg/L | Arsenic and its compounds are used in pesticides, herbicides, pesticides, and many alloys. | Carcinogens include arsenic and inorganic arsenic compounds. Skin cancer is frequently found in studies of people who have consumed drugs, water containing inorganic arsenic for an extended period of time, or have been exposed to arsenic at work. | ||||||||
| 5 | Cadmium | 0.005 mg/L | Extracted as a by-product from zinc or cadmium sulfate ore. It is mostly used to protect other metals from corrosion and rust, such as electroplated steel, iron products, copper, brass and other alloys. Another use is to make a bright yellow pigment called cadmium yellow, which can be used as a high-grade paint and painting pigment. | Cadmium can cause respiratory tract irritation. Long-term exposure can result in loss of smell, gingival macula, and progressive yellow circles. Cadmium compounds are not easily absorbed by the intestine, but can enter the body through breathing and accumulate in the liver or kidneys, causing harm, particularly kidney damage. It can also cause osteoporosis and softening of the bones. | ||||||||
| 6 | Chromium (Hexavalent) | 0.05 mg/L | Chromium is an essential trace element of the human body. Trivalent chromium is an element that is beneficial to the human body, while hexavalent chromium is toxic. Natural water does not contain chromium. The average concentration of chromium in seawater is 0.05 μg/L, lower in drinking water. The sources of chromium pollution are sewage discharged from the processing of chromium-containing ore, metal surface treatment, leather tanning, printing and dyeing. | Trivalent chromium is an important blood sugar regulator and promotes growth and development. It can help insulin promote the efficiency of glucose into the cell. Hexavalent chromium is a highly toxic heavy metal that easily enters human cells, damaging internal organs (such as the liver and kidneys) and DNA. Accumulation in the human body is carcinogenic and has the potential to cause genetic mutations. | ||||||||
| 7 | Lead | 0.01 mg/L | Lead is one of the three major heavy metal pollutants, which is a heavy metal element that seriously endangers human health. Ideal lead content in the human body is zero. | The human body obtains lead primarily through ingesting food and drinking tap water. 90% of the lead that enters the human body is stored in the bones, while 10% is distributed to various tissues and organs throughout the body via blood circulation, affecting red blood cells as well as brain, kidney, and nervous system function. More than 30% of lead absorbed by infants and young children is retained in the body. It has an impact on infants' and young children's growth and intellectual development. | ||||||||
| 8 | Mercury | 0.001 mg/L | Mercury is a naturally occurring element found in air, water and soil. Mercury is a highly toxic, non-essential element that is widely found in a variety of environmental media and food chains, especially fis. | Mercury is extremely toxic to humans and has been linked to Minamata disease in Japan. The kidney is the primary organ affected by inorganic mercury, while organic mercury harms the central nervous system. Organic mercury is more dangerous to humans. | ||||||||
| 9 | Cyanide | 0.05 mg/L | Cyanide refers specifically to a compound with a cyanide group (CN). Cyanide is usually a toxic and lethal substance. | It damages the brain, resulting in central respiratory failure and death. Furthermore, the hydroxide ions released by cyanide in the digestive tract are corrosive. Inhaling high concentrations of hydrogen cyanide or swallowing large amounts of cyanide can cause people to die in a "electric shock" fashion within 2-3 minutes. | ||||||||
| 10 | Fluoride | 1.0 mg/L | Fluoride refers to fluoride-containing organic or inorganic compounds. Fluorine is widely present in natural wate, and it is contained in all tissues of the human body. But it mainly accumulates in teeth and tendons. | Appropriate fluoride is required by the human body. Fluoride in excess is toxic to the human body. 6-12 grams of sodium fluoride is lethal to humans. Skeletal fluorosis can appear after drinking water containing 2.4-5 mg/liter. | ||||||||
| 11 | Nitrate (In N) | 10 mg/L | Nitrates are widely found in the natural environment (water, soil, plants). Among them, nitrate is one of the natural ingredients in plants. Since plants, molds, and human oral and intestinal bacteria have the ability to convert nitrite into nitrite salts, nitrates often manifest themselves as nitrite toxicity | In the human body, nitrates can be converted to nitrites. Nitrite in high concentrations can directly poison people. It is a carcinogenic, teratogenic, and mutagenic substance when it reaches a certain dose in the human body, and it can seriously endanger human health. | ||||||||
| 12 | Trichloromethane | 0.06 mg/L | Trihalomethane generally rarely exist naturally in water. In the process of disinfection in water purification plants, it is formed by reaction of organic matter and chlorine in water. | In animal tests, some have mutagenic and/or carcinogenicity, and some have teratogenic and/or neurotoxic effects, which can cause liver, kidney, and intestinal tumors. | ||||||||
| 13 | Monochlorodibromomethane | 0.1 mg/L | ||||||||||
| 14 | Dichlorobromomethane | 0.06 mg/L | ||||||||||
| 15 | Bromoform | 0.1 mg/L | ||||||||||
| 16 | Trihalomethane (Sum Of Trichloromethane, Monochlorodibromomethane, Dichlorodibromomethane, Tribromomethane). | The sum of the measured concentrations of the various compounds in this class of compounds and their respective limits does not exceed 1 | ||||||||||
| 17 | Dichloroacetic Acid | 0.05 mg/L | It is the main by-product of disinfection of drinking water using liquid chlorine and chlorine dioxide. | Dichloroacetic acid is in the list of class 2B carcinogens. It is mutagenic, teratogenic and carcinogenic. | ||||||||
| 18 | Trichloroacetic Acid | 0.1 mg/L | ||||||||||
| 19 | Bromate | 0.01 mg/L | When water is disinfected with ozone, the bromide reacts with ozone and forms bromate after oxidation. | Bromate is a powerful oxidant that harms the human central nervous system, blood, and kidneys. The International Agency for Research on Cancer has classified it as a Class 2B potential carcinogen. | ||||||||
| 20 | Chlorite | 0.7 mg/L | Chlorite is the main by-product produced when drinking water is disinfected with chlorine gas, chlorine dioxide, etc. | Chlorite reduces blood's ability to deliver oxygen, resulting in methemoglobin and hemolytic anemia. According to the International Cancer Research Centre, it is a carcinogen. | ||||||||
| 21 | Chlorate | 0.7 mg/L | Chlorate is the main by-product produced when drinking water is disinfected with chlorine gas, chlorine dioxide and so on | Chlorate inhibits the absorption of thyroid iodine. | ||||||||
| C. Sensory Traits And General Chemical Indicators | ||||||||||||
| 22 | Chromaticity (Platinum Cobalt Chromaticity Unit) /Degree | 15 | Water quality color isa quantitative indicator of the color of natural water or various treated water. Natural water often shows different colors such as light yellow, light brown, yellow-green and so on. | The cause of the color is due to humus, organic matter or inorganic substances dissolved in water. Different color shades indicate different substances in the water. | ||||||||
| 23 | Turbidity (Scattered Turbidity Units) /Degree | 1 | Turbidity is one of the physical characteristics of water. It describes the extent to which suspended materials in water obstruct light transmission. | In general, the more insoluble substances in the water, the higher the turbidity. Turbidity is formed due to the presence of particulate matter such as clay, sludge, colloidal particles, plankton and other microorganisms in the water. It is used to indicate the clarity or turbidity of the water. It is an important indicator for determining the degree of good water quality. | ||||||||
| 24 | Odor | No odor | Water odor is primarily caused by pollutants in domestic and industrial wastewater, as well as the decomposition of natural substances and related microbial activities. | Although odorless water is not guaranteed to be safe, it is conducive to the trust of drinkers in water quality. | ||||||||
| 25 | Visible To the Naked Eye | no | Suspended solids, floating matter on the water's surface, sediments, microorganisms, and immature juveniles are common visible objects to the naked eye. | Visible to the naked eye indicates the possibility of serious water quality contamination. | ||||||||
| 26 | Ph | 6.6~8.5 | The higher the PH value, the more alkaline the water. The smaller the PH, the more acidic the water. | Alkaline water has a moderate proportion of minerals in it. | ||||||||
| 27 | Aluminum | 0.2 mg/L | Most of the aluminum in tap water comes from alum, which is used as a coagulating precipitant. | Aluminum has been linked to Alzheimer's disease. Aluminum accumulates in concentrated nerve cells in human brain tissue, causing nerve fiber tangle lesions. Furthermore, aluminum inhibits the secretion of gastric juice and acid, lowering pepsin activity and leading to hyperparathyroidism. | ||||||||
| 28 | Iron | 0.3 mg/L | Iron in water mainly comes from minerals and oxides in the earth's crust. Generally, iron in water exists as divalent, trivalent and iron oxides. Proper iron in drinking water is beneficial to the human body. | Too much iron in drinking water can cause symptoms such as loss of appetite, vomiting, diarrhea, gastrointestinal disorders, and stool disorders. | ||||||||
| 29 | Manganese | 0.1 mg/L | Manganese is an essential trace element in the human body and is required for bone structure maintenance. It coexists with iron in natural water. | Long-term low-dose manganese inhalation causes chronic poisoning, tremor paralysis, and serious harm to the human nervous system. Excess manganese, according to recent research, will also damage the arterial lining and myocardium, resulting in atherosclerotic plaque formation and coronary artery stenosis and coronary heart disease. | ||||||||
| 30 | Copper | 1.0 mg/L | Copper is a trace element that is required for life. The amount of dissolved copper in natural water decreases as the pH rises. | Causes stomach upset, vomiting and diarrhea | ||||||||
| 31 | Zinc | 1.0 mg/L | Zinc is one of the essential trace elements of the human body and plays an extremely important role. | Excess zinc can cause strong irritation to the gastrointestinal tract. After absorption, it is mainly stored in the liver and pancreas. Excessive zinc can occur acute poisoning by entering the body through the mouth. | ||||||||
| 32 | Chloride | 250 mg/L | Drinking water and natural water both contain chlorides in the form of potassium, sodium, calcium, and magnesium salts in the water circulation system. If the water flows through a chloride-containing stratum or is polluted by domestic sewage, industrial wastewater, seawater, or sea breezes, the chloride content rises. | The chloride content of the water source generally fluctuates within a certain range. When the chloride content of water suddenly rises, it indicates that the water is polluted. Too much chloride in drinking water can cause the water to have an unpleasant salty taste and can corrode the water distribution system. | ||||||||
| 33 | Sulfate | 250 mg/L | Sulfate is commonly found in drinking water, and the main source is stratum mineral sulfate. It is mostly found as calcium and magnesium sulfates. | The most common physiological reactions to high sulfate intake are diarrhea, dehydration, and gastrointestinal disturbances. | ||||||||
| 34 | Total Solids Of Solubility | 1,000 mg/L | It shows how many milligrams of dissolved solids are dissolved in 1 liter of water. The higher the TDS value, the more dissolved matter is contained in the water. | In general, TDS exceeds 1000mg/L, indicating that various salts and heavy metals in the water may exceed the standard. | ||||||||
| 35 | Total Hardness (In Termsof C Aco3). | 450 mg/L | Refers to the ability of calcium and magnesium ions in water to precipitate soapy water. | Water hardness is the main factor that forms pot scale and affects product quality. | ||||||||
| 36 | Permanganate Index (In O2). | 3 mg/L | Permanganate index is also known as permanganate oxygen demand, permanganate oxidation. Potassium permanganate was used as an oxidant to determine the chemical oxygen demand of aerobic pollutants in water, such as reducing substances such as organic matter, nitrites, ferrous salts and sulfides. It is mainly used to evaluate the quality of drinking water and surface water. | The higher the permanganate index, the more serious the degree of organic contamination of the water. | ||||||||
| 37 | Ammonia (In N) | 0.5 mg/L | Nitrogen in water is mainly present in the form of ammonia nitrogen, nitrate nitrogen, nitrite nitrogen and organic nitrogen. | As long as there is ammonia nitrogen in the water, it indicates that the water body has recently been polluted and that self-purification has not yet been completed. For such raw water, appropriate measures should be taken. Higher ammonia nitrogen concentrations in raw water indicate the presence of new organic contamination. Ammonia nitrogen in drinking water can cause nitrite and odor problems at the pipe network's ends. | ||||||||
| D. Radioactivity Indicators | ||||||||||||
| 38 | Total Α Radioactivity | 0.5 Bq/L | Radionuclides that naturally exist in the natural environment and are produced by human activities are mainly radioactive sources that emit α, β rays. | After radioactive pollutants enter the human body, they continue to emit rays, harm human tissue, and can accumulate in the human body, contributing to diseases such as anemia and malignant tumors, as well as having negative effects on their offspring. | ||||||||
| 39 | Total Β Radioactivity | 1 Bq/L |
To disinfect the finished water, we frequently use ozone, chlorine disinfectants, and other chemicals in the modern water treatment process. As a result, the disinfectant indicators must be tested in the finished water. The general indicators and requirements for domestic drinking water disinfectants are listed in the table below:
| No. | Indicator | Contact Time With Water/Min | Finished Water And Tap Water Limits (Mg/L). | Finished Water Allowance (Mg/L). | Tap Water Allowance (Mg/L). |
| 40 | Free Ammonia | ≥30 | ≤2 | ≥0.3 | ≥0.05 |
| 41 | Total Chlorine | ≥120 | ≤3 | ≥0.5 | ≥0.05 |
| 42 | Ozone | ≥12 | ≤0.3 | – | ≥0.02 |
| 43 | Chlorine Dioxide | ≥30 | ≤0.8 | ≥0.1 | ≥0.02 |
- When disinfecting with liquid chlorine, sodium hypochlorite, or calcium hypochlorite, free chlorine should be measured.
- Total chlorine should be measured when using chloramine disinfection.
- Ozone should be measured when using ozone disinfection.
- Chlorine dioxide concentration should be determined when using chlorine dioxide disinfection.
- Chlorine dioxide and free chlorine should be measured when using a chlorine dioxide and chlorine mixed disinfectant generator.
- Both indicators must satisfy the limit requirements, and at least one must satisfy the allowance requirements.
Each country and region has different implementation standards, and testing of raw and finished water should be done in accordance with your local government’s requirements. Linho would be delighted to share additional experiences and ideas with you.
