Water quality refers to the physical, chemical and biological conditions under which water is in its natural state or after being altered by human action. The concept of water quality has been associated with the use of water for human consumption, on condition that water quality means that it can be used harmlessly. However, depending on other uses, water quality can determined for such uses.
In this context, it is considered that water is of good quality when it is exempt from substances and microorganisms that are dangerous for consumers and exempt from substances that transmit unpleasant sensory sensations for consumption, such as color, odor, taste or turbidity.
To determine the need for treatment and the precise technology treatment, specific contaminants in water must be identified and measured. Water contaminants can be divided into two groups: dissolved contaminants and suspended solids. Suspended solids, such as silt, sand and viruses, are usually responsible for visible impurities. Suspended matter consists of very small particles, which cannot be removed by means of deposition. They can be identified with the description of visible characteristics of water, including turbidity and clarity, taste, color and odor.
- Suspended matter in the water absorbs light, causing the water to have a cloudy appearance. This is called turbidity. Turbidity can be measured by several different techniques; it shows resistance to light transmission in water.
- The sense of taste can detect concentrations of a few tens to several hundreds of PPM and taste may indicate that contaminants are present, but it can’t identify specific contaminants.
- Color may suggest that organic impurities are present. In some cases the color of the water can be caused even by metal ions. The color is measured by comparison of different samples visually or with a spectrophotometer. This is a device that measures the transmission of light in a substance, to calculate concentrations of certain contaminants. When water has an unusual color this usually does not mean a concern for health.
- Odour detection can be useful, because smelling can usually detect even low levels of contaminants. However, in most countries detecting contaminants by smell is limited to strict regulations; it can be a health hazard when some dangerous contaminants are present in a sample.
The total amount of suspended matter can be measured by filtering samples through a membrane and drying and weighing the residue. The suspended matter is expressed in ppm (parts per million), usually mg / l.
The identification and quantification of dissolved contaminants is done by means of very specific methods in laboratories, because these are contaminants that are associated with health risks.
Which Quantitative Analyses Define Water Quality?
Water quality can also be determined by a number of quantitative analysis in the laboratory, such as pH, total solids (TS), the conductivity and microbial contamination.
The pH is the value that determines whether a substance is acidic, neutral or basic, calculated according to the present number of hydrogen ions. It is measured on a scale from 0 to 14, in which in the middle, seven substance is neutral. pH values below 7 indicate that a substance is acidic and pH values above 7 indicates that it is basic. When a substance is neutral the number of hydrogen atoms and hydroxyls is equal. When the number of hydrogen atoms (H +) atoms exceeds the number of hydroxyl (OH-), the substance is acidic.
The pH level has an effect on many stages of water treatment and affects crusting of water sources. The pH level can be determined by various analytical methods such as color indicators, pH-paper or pH meters.
The total solids (TS) is the sum of all dissolved and suspended solids in the water. When water is analysed for ST sample is dried and after that the residue weighed. ST can be organic or inorganic substances, microorganisms, as well as larger particles like sand and clay.
The conductivity means the driving of energy through the ions. The measure of water conductivity can provide a clear view of the ion concentration in the water, because water is naturally resistant to conduction of energy. Conductivity is expressed in Siemens and it is measured with a conductivity meter or a cell.
Microbial contamination is divided into contamination by organisms that have the ability to reproduce and multiply and organisms that cannot. Microbial contamination can be contamination by bacteria, which is expressed as Colony Forming Units (CFU), a measure of the bacterial population. Another microbial contamination is contamination by pirogen. Pirogenes are bacterial products that can induce fever in warm-blooded animals. After Pirogen and bacteria water can also be contaminated by the virus.
The analysis can also be made by measurements of the total organic carbon (TOC) and biological and chemical oxygen demand. BOD is a measure of organic matter in the water, expressed in mg/I. It is the amount of dissolved oxygen required for the decomposition of organic matter. The BOD test takes five days. COD is a measure of the organic and inorganic matter in the water, expressed in mg / l, it is the amount of dissolved oxygen required for full chemical oxidation of contaminants.
If you’re on a public or municipal water line in the United States, call your local water supplier, whose number is on your water bill. By law, the supplier must test its processed water regularly and provide you with a copy of the results, called a Consumer Confidence Report, annually as well as on demand.
Many water agencies across the country now make their annual water quality reports available online. You can access these reports on the Environmental Protection Agency‘s Web site.