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Sewage Treatment Plant (STP)

Water Softeners


Sewage is usually resulted of the disposals from residence, industry, offices, factories and other public outlets. This disposal includes the waste & water from kitchen, bath, toilets, rain waters & other occasionally cleaning operations. Though the waste water coming from the industrial area can not be re-used as it contains the high level of solids & chemicals which made the water color Black where as the disposals or waste coming through household is of grey color which can be recycled and re-used for planting or harvesting. It can also be supplied back to residential or commercial buildings to use it for flushing the toilets. But due to improper sewage system, black water is getting mixed with the grey water for which this treatment is adopted.


Sewage is of usually three types:-

1.Domestic Sewage: This is the result of household chaos. Daily routine work includes bathing, toilet, washing clothes or kitchen utensils, cleaning etc. This kind of disposal are of grey color which is later recycled for re-use purposes. This recycled water is used for further planting, harvesting or for other nature related work. This sewage is also called sanitary sewage. This sewage can be purified with an extent of 99.9% but yet it includes some harmful stuff which cannot be re-used for the same purposes. 

2. Industrial Sewage: This is generated through the activities performed in industry or factory outlets. This contains the poisonous chemicals, solids, oils etc which cannot be dissolved in water and so they ruin the water completely. Their cleanliness percentage resembles only 0 .1% and that’s why it cannot be re-used for any purposes. This sewage is quite smelly and of black color which could results of harmful diseases for the surrounding peoples.

3. Storm Sewage: Rain water and other natural water contain the organic materials which are not at all harmful. Dissolved dust is purified to make it re-usable and supplied through pipelines. 

The main goal of treatment is to make the waste water re-usable or smoothened the flow of water lying on roads or lands or coming from the different outlets. This treatment is performed as per the local, state and federal regulations or standards.


BOD - the full form of which is Biochemical Oxygen Demand and is used to measure the strength of sewage. It is calculated by incubating at 20 degree Celsius for 5 days period and measuring the dissolved oxygen from the beginning till the end of the period. and it is one of the most commonly used measures for the strength of the sewage. 

COD stands for Chemical Oxygen Demand whose value is more than the BODs. It could bring the results within few hours. It is a measure of the amount of oxygen required to chemically oxidize the sewage. 

Process: The treatment process involves the three stages which are as follows:-

Primary treatment is a basic method of cleaning the solids or chemicals from the waste water. In this treatment, water is temporarily stocked in an immovable basin in which heavy solids retained at the bottom surface where as chemicals, light solids or oils float to the above water surface. The settled solutes are removed from the bottom and upper surface and the remnant waste water may be left free or re-cycled through secondary treatment.

Secondary treatment is basically used to remove the biological waste comes through household chaos, such as washing, cleaning or bathing. This treatment is performed through biological process in which micro organisms are separated from the discharged water prior to territory treatment to make the water re-usable.

Tertiary treatment helps is removing more than 90% of solutes which is completely disinfected. This kind of treatment is quite expensive and performed under special circumstances. This treatment is eco-friendly and almost produces the quality of drinking water.

List of alternative secondary treatment methods:

  • Activated sludge.
  • Aerated lagoon.
  • Aerobic granulation.
  • Constructed wetland
  • Membrane bioreactor
  • Rotating biological contactor
  • Trickling filter

Effluent Treatment Plant (ETP)

Water Softeners

Water is most important part in everyone's life whether it belongs to personal life or industrial life. No one can live without water and even no production can occur without it. So it becomes necessary to utilize the available water to the maximum extent or not to destroy the same hazardously. However, the quantity used by different industries may be differ due to different usage but still much of the important task such as washing, drinking, dilution etc. are performed through water only. If the industry has a right to use the water then it becomes their duty to make it clean or re-usable. Industries consumed the clean water and generate the polluted water which includes harmful chemicals; oils, grease, solids etc. water produced through the industrial process is treated as called "waste water" or "Effluent".

Here the main work starts to clean the pollutants through the effective water treatment. So plants are established for this process and these plants are called "Effluent Treatment plant". As the name suggest, it involves removing the pollutants under the water to make it usable for another process and so to make the environment pollution free.


  • Discharge waste free water.
  • Eliminates municipal fees.
  • Production materials can be recovered for re-use.
  • Recycling of water so eliminates unused water.

According to Department of Environment, effluent must be according to the quality standards set by the government and so the ETP should be established and directed accordingly.


various strategies are being used for waste water treatment:-

• Brine Treatment: This technology includes the membrane filtration processes, ion exchange processes, evaporation processes etc. every process has its own unique task to filter the water. Basically brine treatment is used to remove the dissolved salt ions or other metals from the water and to maximize the recovery of fresh salts & water.

• Solids Removal: solids can be removed through filtration or extra filtration to make the water re-usable.

• Removal of Bio-Degradable organics: It is based on the sewage treatment used to clean the rain water etc.

• Oils and grease removal: Before using membrane filtration, skimming process can be used to remove the oil or grease from the upper surface of water. Skimming is cost-efficient method to clean the oiling or grease water through the cleaning depends on the solids dissolved in the water. Many oil refineries, chemical plants, natural gas plants are producing effluent water which contains high amount of oils, chemicals & grease etc. These industries use a device called API oil water separator salt which separates the oil and wastewater by knowing the gravity difference between them. API denotes the American petroleum institute who had published the standards to design this separator.

• Activated sludge process: It is used to treat sewage & industrial waste water through the following process:-

- Aeration tank is used to inject air in to the mixed waste water
- A settling tank is used to settle the waste sludge.

• Trickling filter process: This is one of the oldest method of treating the sewage or waste water through forcing air flow with the help of plastic bed or by natural convection of air.

• Treatment of other organics: it includes adsorption, vitrification, oxidation processing etc to clean the paints, solvents, pesticides etc from the water.

• Treatment of acids and alkalis, toxic materials: Toxic materials include zinc, silver etc. which are hard solids which are to be clean with the use specific treatment as per the solids nature.

While processing ETP, you must consider the following steps:-

  • Which type of solid is present?
  • The level of waste water.
  • What process is suitable?
  • What is the cost budget?
  • Cleaning ratio?

Thus effluent treatment plant is designed according the solids and waste dissolved in the water to make it clean and usable again. Kelvin Water Technologies has gain popular name with in short span of period for serving India in the area of repair and maintenance of Effluent Treatment Plants with the help of professionals.