Wastewater treatment:
what it is, process and machinery

Sewage is a necessary evil, the result of using this precious resource. But the truth is that in order to keep the water as clean as possible, wastewater must not end up in the seas and lakes. So it is important to know about wastewater treatment and what processes are involved.

What is waste water?

Wastewater is water that has already undergone a process of use and therefore has lost its characteristics to be used again. It is water that has lost its value for the immediate purpose for which it was intended. Moreover, their quality has been affected and they are not suitable for human consumption or irrigation.

These waters come from domestic and industrial use, although they can also be derived from urban use. In terms of characteristics, they are generally of a different colour to ordinary water, may have a foul odour and are sometimes accompanied by solid waste. This is why they can be harmful and polluting waters.

According to the WHO, up to 80% of sewage is released into seas and lakes untreated. So it is important to know how the water can regain its warmth and not pollute the environment.

What is wastewater treatment?

Wastewater treatment is the chemical, physical and biological processes used to remove pollution and impurities produced as a result of use. The treatment of this type of water seeks to purify it for one of two purposes, reuse or return it to the sea in suitable conditions.

There are different methods of wastewater treatment. However, three of them stand out. The primary decanter, which uses gravity to promote sedimentation, and the dissolved air flotation, which seeks to separate particles by means of bubbles. Finally, there are the chemical processes, which involve the use of chemical substances.

It is also possible to apply mechanical sedimentation procedures, which may include the use of screens or filters to remove waste. Wastewater treatment plants are used to carry out such treatments..

How wastewater treatment is carried out: process steps

In order to achieve a complete treatment of polluted waters, several steps must be followed. In addition, these ensure the further removal of pollutants in order to reduce the level of pollution in the waters of lakes and seas.

Mechanical treatment

The first step or stage through which wastewater must pass is mechanical treatment. In this stage, up to 30% of the solid waste in the water can be removed. First, the water passes through a series of screens or sieves that collect the larger waste.

After this they go to a sand collection process, for which a sedimentation process is used at a high flow velocity. After which the water passes to the primary treatment tank, where with a much lower velocity the remaining particles are pushed to the bottom or to the surface.

Biological purification

After mechanical treatment, biological purification must be carried out, which includes passing the water through aeration tanks. These are basically circulation tanks in which oxygen is added to the water. Under these conditions micro-organisms feed on the pollutants, which produces sludge sediments that float on top of the water.

After this process the water passes to secondary tanks, where the water velocity is again reduced. In these tanks, sedimentation takes place, which carries the waste to the bottom of the tank. At this point the water is already 90% purified.

Chemical treatments

A series of chemicals are then added to the water in order to improve its condition and reach the established drinking standards. Chemicals are applied to achieve disinfection, neutralisation, phosphate precipitation, as well as nitrogen removal. These chemicals are not harmful to health and make the water drinkable.

Nanofiltration processes

To remove any impurities, a very fine membrane is used to prevent the smallest particles from passing through. It can even filter out metal ions and even molecules. This ensures that the water is completely clean and can be used for human consumption.

With these steps, a complete wastewater treatment can be achieved.

Types of wastewater treatment

Different types of processes are applied in wastewater treatment, which are described below.

Primary treatment

This type of treatment is known as a pretreatment that aims to remove solid waste from the water. This reduces the pollutant load of the water and allows you to meet the final effluent requirements. This can include various processes, such as filtration or flocculation.

Secondary treatment

This is a biological water treatment that uses bacteria and micro-organisms to break down pollutants in the water. This allows the pollution to solidify and be more easily removed.

Tertiary treatment

It seeks to clean the water of specific pollutants, such as phosphorus, minerals, viruses, heavy metals, nitrogen and micro-organisms. To achieve this, it combines chemical and mechanical processes.

Specialised machinery for wastewater treatment

In order to achieve complete wastewater treatment, specialised machinery must be used. This may include special tanks as well as a series of filters. But not all are chemical, it is important to use sluices and valves to transport the water from one tank to another. Also, you must also have mechanisms that allow you to test the water.

Domfesa manufactures different machines that help in the transport, channelling and filtering of water:

We have a liquid elevator capable of lifting water with solids and sludge in it. Our lifting system offers our customers safety and efficiency, as they do not have to worry about the common problems of blockages and cavitations. + info: liquid and solid pumps.

We can supply flushers and valves from 10 mm in diameter up to 3000 mm, completely watertight. If required, they are able to regulate the flow rate during the treatment process. + info: cutters – shavers.

We have separators for liquids and solids both by means of conveyors and screw conveyors, with the option of customising the final production granulometry. + info link 1 : screw conveyors

+info link 2: redler chain conveyor.

All our machines are calculated and adapted to our customers in order to maximise their energy efficiency.
All this equipment and machinery can be found at Domfesa, a company specialising in mechanisms for water treatment plants.