Waste Water is defined as water which carries wastes from homes, industries, businesses or any other sources. It is usually a mixture of water and dissolved or suspended solids. Since water is becoming a scarce commodity, hence it is imperative to evolve technologies which treat them efficiently so that they can be reused. Treatment is also necessary because it helps in the reduction of physical, physiological, radioactive,biological and chemical pollutants.

Types of Waste Water Treatment Plants
Depending on the nature of the Waste Water to be treated, Waste Water can be classified as:

Sewage Treatment Plants
Sludge Treatment Plant
Industrial Waste Water Treatment
Agricultural Waste Water Treatment Plant
Radioactive Waste Water Treatment Plant
Recycling Waste Water Treatment Plant

Effluent Treatment Method

Effluent treatment method consists of following process-Coagulation, Flocculation, Sedimentation, Filtration, Chlorination, Softening. For the best results these process should be followed in sequence. The water so treated can be used again for any industrial or other process. In some effluent plants however, sedimentation/settling units are used for primary as well as for the secondary treatment of solid liquid separation. These solids are present in colloidal forms which are are removed primary sedimentation/ setting tanks of clarifier.

Wastewater Treatment Methods

Wasterwater is treated in following stages:

Pre-Treatment is a process which involves the passing of the effluent through the screen chambers to remove large floating solid particles which are settled in the primary sedimentation tanks. In this process apart from pre-chlorination, heavy suspended impurities are also removed.

Water Treatment Plant

Primary Treatment
Primary treatment includes chlorination, sedimentation and sludge digestion. Sludge digestion takes place in a sludge digester in which the organic or inorganic wastes and solids removed from sedimentation are are subjected to anaerobic fermentation. Since inorganic suspended solids hinders the performance of the biological oxidation of organic matter hence their removal is necessary. Removal of organic suspended solids present in the effluents reduce the aeration tank volume requirement which provides a primary clarification system prior to aerobic biological treatment process.

Secondary Treatment
In a secondary treatment process bio solids are separated from the water. Here soluble organic matter is biologically oxidized in the presence or the absence of oxygen. The process mainly removes dissolved organic matter and reduces biological oxygen demand. Whole process takes place in a secondary treatment system. A good secondary system has surface overflow rate of 16-80 metre cube/ meter square of the clarification area per day.

Tertiary Treatment
Tertiary treatment is primarily used to recycle water for industrial reuse. It may be also use if the effluent from a secondary treatment plant is not satisfactory. The process used in tertiary treatment system are filtration, demineralization and the reverse osmosis process.
Integrated Wastewater Treatment Plant in a Beach Area

Stages of Sewage Treatment

Sewage treatment is accomplished in three stages which are as follows:

Primary Treatment
In a primary treatment wastewater is relieved from the contaminants like coarse sands, pebbles, organic and inorganic wastes, fatty substances etc. The wastewater consist of large objects like rags, cans, tin etc which are removed by screen. This is necessary because the presence of these objects can harm the sensitive parts of the plant. Followed by the screen there is a a grit chamber that are used for removing sand and other heavy inorganics. The materials so collected in the grit chamber are collected and bagged for disposal.

The liquid being freed from grit is passed to through the fixed or rotating screens in order to get rid of floating and larger materials. Some plants use sedimentation stage in which the sewage is passed through large tanks which are called as primary clarifiers or primary sedimentation tanks. In these tanks floating materials are removed and homogeneous liquid is ready for the biological treatment whereas, the sludge is is separated for the separate treatment. Primary tanks consist of scrapers that drive the sludge towards a hopper in the base of the tank. From here the sludge is pumped out for treatment.

Secondary Treatment
Secondary treatment method uses aerobic biological processes to degrade the biological content of the sewage like human waste, food waste, soaps and detergent. In this method bacteria and protozoa convert the biodegradable soluble organic contaminants into floc.

In Secondary treatment systems two methods viz. fixed film and suspended growth are used. In these methods sewage passes over the surface of the biomass which grows on the media. Of these two systems fixed film system is preferred as it can easily cope with drastic changes in the amount of biological material and can provide higher removal rates for organic material and suspended solids than suspended growth systems.

For strong organic loads sometimes Roughing filters used. These filters usually consists of tall, circular filters which are filled with open synthetic filter media where sewage is applied at a relatively high rate. These filters are fabricated to for high hydraulic loading and a high flow-through of air.

Secondary Sewage Treatment Process

Activated sludge plants are also used in secondary treatment that use use dissolved oxygen to promote the growth of biological floc which aids in the removal of the organic material. It is also capable of trapping particulate material and can, convert ammonia to nitrite and nitrate ultimately to nitrogen gas. If plant is receiving more variable loads then trickling filter beds can be used.

In secondary treatment Biological Aerated Filter (BAF) is also used which consist of reactor filled with a filter media. The media supports highly active Biomass that is attached to it and filter suspended solids. Carbon is reduced and ammonia is converted in aerobic mode.

In the final stage of secondary treatment biological floc is settled and material is filtered. The sewage water so produced after this treatment contains very low levels of organic material and suspended matter.

When the sewage is passed through rotating biological contractors (RBCs) the microorganism which covered the surface of the RBCs reduce the BOD and further remove suspended matter from the wastewater.

Tertiary treatment
Wastewater is given tertiary treatment to further enhance its quality before they are discharged in the environment. The popular methods that are used in this stage are filtration, lagooning, removal of chemicals like nitrogen and phosphorus etc.

Different treatment processes are required to remove nitrogen and phosphorus. Nitrogen is removed through the biological oxidation of nitrogen from ammonia to nitrate, followed by denitrification, the reduction of nitrate to nitrogen gas which is removed to the atmosphere. Phosphorus on the other hand can be removed by using two process that is by the use of specific bacteria, called polyphosphate that accumulate large quantities of phosphorus within their cells they are removed from the water ans are used as fertilizer. Chemical precipitation can also be used to remove phosphorus. Wastewater is sometimes further disinfected by using chlorine, ozone gas and ultraviolet light.

Effluent is any substance that create pollution, such as municipal sewage or industrial liquid waste that flows out of a treatment plant, septic system, pipe, etc. Effluent can be the outflow from a sewage treatment facility or the wastewater discharge from industrial facilities. Effluents are being produced in large amounts from a number of industries, and it is posing a serious threat to our environment. Handling of such type of effluents is quite necessary to prevent our environment from being further threatened by such dangers.

Effluent Treatment Plant

The effluent treatment plant may follow any of these processes available today, such as conventional method, modern technology. Here we will concentrate on the conventional method used for the effluent treatment plant. The conventional method consists of three main stages, which includes:

  • Primary Treatment
  • Secondary Treatment
  • Tertiary Treatment

Primary Treatment

The primary treatment process consists of three processes including, physical treatment, chemical treatment, and biological treatment. The physical treatment includes the separation of solid and semi-solid materials from the the effluent. This phase use equipment, such as grit chamber and bar screen. After the physical processing is over, the effluent is treated chemical, which includes the processes like coagulation and flocculation. After the removal of solid materials and chemical treatment, the effluent is passed through a biological treatment process.

Secondary Treatment

The secondary treatment includes the following processes in the entire treatment including, Activated Sludge Process, Aerobic/Anaerobic Digestion, Sequence Batch Reactor, Tricking Filter, Oxidation Pond. These two are the major ones.

Activated Sludge Process: This process uses dissolved oxygen to promote the growth of biological floc which helps in removing the organic material. It can convert ammonia to nitrite and nitrate and ultimately to nitrogen gas. This process is also capable of trapping particulate material.

Aerobic/Anaerobic Digestion: Aerobic biological processes are used to decompose the biological content of the sewage like food waste, soaps, detergent and human waste. Bacteria and protozoa are introduced to convert the biodegradable soluble organic contaminants into floc.

Tertiary Treatment

Tertiary treatment of wastewater is essential to further enhance its quality. Some popular methods used in this stage are filtration, lagooning, removal of chemicals like nitrogen and phosphorus etc. Various treatment processes are used to remove nitrogen and phosphorus. The ammonia present in the wastewater is changed to nitrite and it is followed by denitrification. Phosphorus can be removed by using specific bacteria, called polyphosphate that collects large quantities of phosphorus within their cells. They are removed from the water and are used as fertilizer.

Waste Water Treatment Recycling


We have great tendency to work out the most economical solution for the treatment of your waste water not only to comply the legal requirements of National Environmental quality standards (NEQS) limits but also make your wastewater useable in horticulture application in your company.

We offer a combination of chemical and biological treatment, which also reduces the chemical consumption cost. The biological constituents have potency to be reused for a long time, therefore you don’t need to spend huge amount of money as an operational cost of the wastewater treatment project.

Click Here National Environment Quality Standards (NEQS)

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