– Underground well water:
- Rotten egg smell: due to the presence of H2S gas, a result of the decomposition of organic matter in the ground and dissolution into groundwater
- The fishy smell of iron and manganese.
– Surface water (rivers, streams, ponds): The fishy smell of algae: due to the appearance of algae and microorganisms. In this case, the water is usually green.
– Tap water: The smell of disinfectant chemicals (chlorine) remains in the water
A strange taste will cause discomfort when using water. Depending on the type of taste, there are appropriate treatment methods such as using chemicals to kill algae in ponds, coagulation and filtration, adsorption with activated carbon, etc.
- The yellow color of iron and manganese compounds.
- Green color of algae, organic compounds.
Highly colored water often causes sensory discomfort. Treatment processes such as ozone aeration, prechlorination, flocculation, and sedimentation can reduce the color of water. It should be noted that when the water source is colored due to organic compounds, the use of chlorine chemicals can create a new substance, trihalomethane, which can cause cancer.
Domestic water standards stipulate that water color is less than 15 TCU.
- Water sources with a pH greater than 7 often contain many carbonate and bicarbonate ions (due to flowing through many layers of soil and rock).
- Water sources with a pH less than 7 often contain many acidic ions.
Currently, there is no specific evidence linking pH and users’ health. According to the Standard, the pH of water used for domestic use is 6.0 – 8.5 and the pH of drinking water is 6.5 – 8.5. However, carbonated soft drinks have a pH of 2.0 – 4.0. Foods usually have pH = 2.9 – 3.3.
In water supply pipes, the pH value of water is related to the corrosiveness of equipment and water containers. Especially in low pH environments, the disinfection ability of chlorine will be stronger. It should be noted that when the pH is greater than 8.5, if there are organic compounds in the water, disinfection with chlorine can easily form the carcinogenic compound trihalomethane.
Turbidity is a measure of the amount of suspended matter in water, usually due to the presence of colloids, clay, algae and microorganisms.
Cloudy water causes sensory discomfort, in addition to the possibility of microbial contamination.
Clean water standards stipulate turbidity to be less than 5NTU, but the maximum limit for drinking water is only 2 NTU. Treatment processes such as flocculation, sedimentation, and filtration contribute to reducing water turbidity.
Indicators Degree KiResponsem
The alkalinity of water is caused by bicarbonate, carbonate and hydroxide ions.
In the chemical composition of water, alkalinity is related to other indicators such as pH, hardness and total mineral content. Determining the alkalinity of water helps quantify chemicals in the flocculation process, water softening as well as anti-corrosion treatment.
Currently, there is no specific evidence linking alkalinity and users’ health. Normally, water used for drinking should have an alkalinity lower than 100 mg/l.
Indicators of Degree Cofng
Hardness is a measure of the total multivalent cations in water, most commonly calcium and magnesium ions.
Hard water often requires more soap to create lather, or causes white scale build-up in heaters, hot water pipes, radiators or boilers. In contrast, hard water usually does not cause corrosion of pipes and equipment. Surface water usually does not have as high hardness as groundwater.
Currently, depending on the hardness of water, people divide it into the following types:
- Hardness = 0 – 50mg/l -> Soft water
- Hardness = 50 – 150mg/l -> The water is a bit hard
- Hardness = 150 – 300mg/l -> Hard water
- Hardness > 300mg/l -> The water is very hard
According to clean water standards, hardness is regulated to be less than 350 mg/l. For drinking water, hardness is less than 300 mg/l. However, when the hardness exceeds 50 mg/l, white residue appears in the cooking equipment. In the composition of hardness, calcium and magnesium are two important elements that are often supplemented to the body through food. Except for kidney stone diseases, it is necessary to limit the absorption of calcium and magnesium at high levels.
Hardness can be removed by ion exchange method. After each filtration cycle, the cation resin is regenerated with a salt solution.
Learn more about the hard water treatment softener system here
Indicators Thechal tdissolvedn (TDS)
TDS is a measure of total dissolved solids in water, also known as total minerals.
Clean water standards stipulate that TDS is less than 1,200 mg/l. Drinking water standards stipulate that TDS is less than 1,000 mg/l.
Indicator Degree ofoxidation (organic matter)
Oxidation level is used to evaluate the pollution level of water sources.
There are two methods to determine the degree of oxidation depending on the chemicals used: KMnO4 and K2CrO7 methods.
Clean water standards stipulate that the oxidation level according to KMnO4 is less than 4 mg/l. Drinking water standards stipulate that the oxidation level (according to KMnO4) is less than 2 mg/l.
Aluminum is the main ingredient in mineral rocks and clay. Aluminum is used in industries producing semiconductors, dyes, paints and especially coagulation chemicals in water treatment. Water extracted from acidic soils often has low pH and high aluminum content.
Aluminum does not cause metabolic disorders, but is associated with Alzheimer’s disease and accelerated aging. Drinking water standards stipulate aluminum content to be less than 0.2 mg/l.
Because iron two ions are easily oxidized to iron three hydroxide, self-precipitate and settle, iron rarely exists in surface water. For groundwater, in anoxic conditions, iron often exists in the form of Fe2+ ions and is dissolved in water. When ventilated, iron two will convert into iron three, a yellow iron hydroxide precipitate appears, and is easy to settle. In cases where the water source has a lot of organic matter, iron can exist in colloidal form (organic complex) which is very difficult to handle. In addition, when water has a low pH, it will cause corrosion of pipes and containers, increasing the iron content in the water.
Iron is not toxic to the body. When the iron content is high, the water will have a fishy taste, yellow color, increased turbidity and color, making it difficult to use. Drinking water and clean water standards both stipulate iron content of less than 0.5 mg/l.
Manganese often exists in water along with iron but in lower concentrations. When there is manganese in the water, it often creates a black residue that sticks to the walls and bottom of the tank.
Manganese has very low toxicity and does not cause cancer. At concentrations higher than 0.15 mg/l, it can create an unpleasant taste and stain clothes. Drinking water and clean water standards both stipulate manganese content of less than 0.5 mg/l.
Arsenic indicator (credit)
Due to seeping through many different geological layers, groundwater often contains more arsenic than surface water. In addition, arsenic is present in water sources when contaminated with industrial wastewater and pesticides.
When contaminated with arsenic, it can cause skin and lung cancer. Clean water standards stipulate arsenic to be less than 0.05 mg/l. Drinking water standards stipulate arsenic to be less than 0.01 mg/l. Learn more about Arsenic toxicity and how to handle it here
Due to seeping through many different geological layers, groundwater often contains more cadmium content than surface water. In addition, cadmium is present in water sources when contaminated with industrial mining wastewater and landfill leachate. Cadmium can appear in galvanized steel pipes if corrosion occurs.
Cadmium has negative effects on the kidneys. When highly toxic, it can cause vomiting. Drinking water standards stipulate that Cadmium is less than 0.003 mg/l.
Chromium is present in water sources when contaminated with industrial wastewater from mining, plating, leather tanning, dyes, paper production and ceramics.
Hexavalent chromium is more toxic than trivalent chromium and has negative effects on body parts such as the liver, kidneys, and respiratory organs. Acute poisoning can cause bleeding, dermatitis, and ulcers. Chromium is classified as a group 1 poison (likely to cause cancer in humans and pets). Drinking water standards stipulate that chromium is less than 0.05 mg/l.
Copper is present in water due to corrosion on pipes and equipment made of copper or brass. Algae-killing chemicals widely used on lakes and ponds also increase copper levels in water sources. Wastewater from metallurgy, plating, leather tanning, pesticide, herbicide or film factories also contributes to increasing the amount of copper in water sources.
Copper does not accumulate in the body to the point of being toxic. At a concentration of 1-2 mg/l, the water has an unpleasant taste, and cannot be drunk when the concentration is as high as 5-8 mg/l. Drinking water and clean water standards both stipulate copper content of less than 2 mg/l.
In natural water sources, only 0.4-0.8 mg/l of lead was detected. However, due to industrial wastewater pollution or pipe corrosion, lead can be detected at higher levels in drinking water.
When lead levels in the blood are high, it can cause brain damage, digestive disorders, muscle weakness, and destruction of red blood cells. Lead can accumulate in the body to high and toxic levels. Drinking water and clean water standards both stipulate lead content to be less than 0.01 mg/l.
Zinc is rarely present in water, except through contamination from wastewater from ore mining areas. Zinc has not been found to be toxic to the human body, but at levels > 5 mg/l made the water milky white. Drinking water and clean water standards both regulate zinc content < 3mg/l.
Nickel is rarely present in water, except for contamination from wastewater from the electronics, ceramics, battery, and steel industries.
Nickel has low toxicity and does not accumulate in tissues. Drinking water and clean water standards both stipulate nickel content to be less than 0.02mg/l.
Indicator ThEmploymentof Treasury
Mercury rarely exists in water. However, mercury salts used in mining technology have the potential to pollute water sources.
When poisoned by mercury, organs such as the kidneys and nervous system will be disturbed. Drinking water and clean water standards both stipulate mercury content to be less than 0.001 mg/l.
Molybdenum is rarely present in water. Molybdenum is often found in wastewater from the power industry, petrochemical industry, glass, ceramics and dyes.
Molybdenum is easily absorbed in the digestive tract and attacks organs such as the liver and kidneys. Drinking water standards stipulate molybdenum to be less than 0.07 mg/l.
Water sources with high chloride content are often due to osmosis from seawater or due to pollution from wastewater such as galvanizing, oil exploitation, paper production, and water production from softening processes.
Chloride is not harmful to health. The maximum limit of chloride is selected according to the sodium content in water. When combined with chloride, it will cause a salty taste that is difficult to drink. Clean water standards stipulate that chloride is less than 300 mg/l. Drinking water standards stipulate chloride to be less than 250 mg/l.
Ammonium – Nitrite – Nitrate indicator
Common forms of nitrogen compounds in water are ammonium, nitrite, nitrate, the result of the decomposition of organic matter or due to pollution from wastewater. Among them, ammonium is the most toxic substance to fish and aquatic species. Nitrite is formed from the decomposition reaction of organic nitrogen and ammonium and with the participation of bacteria. The nitrite will then be oxidized to nitrate. In addition, nitrates are also present in water sources due to wastewater from chemical industries, fields using chemical fertilizers, landfill leachate, and rainwater runoff. The presence of nitrogen compounds in the chemical composition of water shows signs of water pollution.
Clean water standards stipulate that ammonium is less than 3mg/l. Drinking water standards stipulate that ammonium is less than 1.5 mg/l.
Clean water and drinking water standards stipulate that Nitrite is less than 3mg/l, Nitrate is less than 50mg/l.
Sulfates are often present in water due to the oxidation of organic substances containing sulfides or due to pollution from wastewater from textile dyeing, tanning, metallurgy, and paper production industries. Aluminum-contaminated water often contains high levels of sulfate.
At a sulfate concentration of 200mg/l the water has an acrid taste, higher concentrations can cause diarrhea.
Drinking water standards stipulate sulfate to be less than 250 mg/l.
Surface water usually has a low fluorine content of about 0.2 mg/l. For groundwater, when flowing through limestone, dolomite, and clay layers, the fluorine content in water can be as high as 8-9 mg/l.
Research results show that when fluoride content reaches 2 mg/l, it darkens teeth. If you regularly use water with a fluoride content higher than 4 mg/l, it can cause bone rot. Fluorine does not show signs of causing cancer. Drinking water standards stipulate fluorine content in the range of 0.7-1.5 mg/l.
Cyanide is present in water sources due to pollution from wastewater from the plastic industry, plating, metallurgy, chemicals, and synthetic fibers.
Cyanide is very toxic, often attacking organs such as the lungs, skin, and digestive tract. Drinking water and clean water standards both stipulate a xuanide content of less than 0.07 mg/l.
Coliform bacteria (commonly known as Escherichia Coli) are often found in the human digestive system. The discovery of Coli bacteria showed that the water source showed signs of pollution.
Drinking water and clean water standards both stipulate that the E. Coliform content is 0. Total Coliform in clean water is allowed at 50 bacteria / 100 ml.