Sulfate in Drinking Water

Sulfate is a substance that occurs naturally in drinking water. Health concerns regarding sulfate in drinking water have been raised because of reports that diarrhea may be associated with the ingestion of water containing high levels of sulfate. Of particular concern are groups within the general population that may be at greater risk from the laxative effects of sulfate when ... Read More »


Hydrazine, N2H4, is a molecule in which one hydrogen atom in NH3 is replaced by an −NH2 group. The pure compound is a colourless liquid that fumes with a slight odour similar to that of ammonia.   Role of Hydrazine in Water Treatment: What is hydrazine?   There are two types of hydrazine: anhydrous hydrazine (N2H4) and hydrazine hydrate (N2H4・H2O).Hydrazine ... Read More »

Dyes and Pigments

The residual dyes from different sources (e.g., textile industries, paper and pulp industries, dye and dye intermediates industries, pharmaceutical industries, tannery, and Kraft bleaching industries, etc.) are considered a wide variety of organic pollutants introduced into the natural water resources or wastewater treatment systems. ·         Dyes and pigments are substances that impart color to a material. The term colorant is ... Read More »

Organic Matter

Definition: Organic Matter is any sort of material that was once alive.   Why does it cause pollution? Micro-organisms, such as bacteria, make a living by eating organic matter. When you and I eat a sandwich we use oxygen in our bodies to break down the carbon. Bacteria use oxygen in the same way to break down organic matter. If ... Read More »


Water pollution by chemicals (such as detergents) is a big concern in the global context. Many laundry detergents contain approximately 35 percent to 75 percent phosphate salts. Phosphates can cause a variety of water pollution problems. For example, phosphate tends to inhibit the biodegradation of organic substances. Non-biodegradable substances cannot be eliminated by public or private wastewater treatment. In addition, ... Read More »


Chlorides are widely distributed in nature as salts of sodium (NaCl), potassium (KCl), and calcium (CaCl2).   EFFECTS ON water: Chloride increases the electrical conductivity of water and thus increases its corrosivity. In metal pipes, chloride reacts with metal ions to form soluble salts , thus increasing levels of metals in drinking-water. In lead pipes, a protective oxide layer is ... Read More »

What is Hard Water?

Water is considered hard when it has a relatively high concentration of calcium and magnesium ions (two of the salts which make up TDS). Hard water received this name because it requires more soap to get a good lather and makes the water “hard” to work with. Water hardness can be reported in milligrams per liter, parts per million (which ... Read More »

Total dissolved solids

Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions.   Total dissolved solids (TDS) is a measure of the combined content of all inorganic and organic ... Read More »

chemical oxygen demand

In environmental chemistry, the chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers) or wastewater, making COD a useful measure of water quality. It is expressed in milligrams per liter (mg/L) also referred ... Read More »

Biological Oxygen Demand

Biochemical Oxygen Demand (BOD) refers to the amount of oxygen that would be consumed if all the organics in one liter of water were oxidized by bacteria and protozoa (ReVelle and ReVelle, 1988). The first step in measuring BOD is to obtain equal volumes of water from the area to be tested and dilute each specimen with a known volume ... Read More »