Pre-Treatment

Pre-Treatment

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Water and Wastewater Pre-Treatment Process

The pre-treatment process is one of the most important steps in the overall water and wastewater treatment process. The purpose of the pre-treatment stage is to remove disturbing factors such as some impurities, solids, suspended colloidal particles, and living organisms in the wastewater. One of the most important benefits that this process gives us is to ensure the final water quality is up to our standards. Pre-treatment processes allow your water and wastewater quality to be protected from factors such as seasonal changes, industrial pollution, and severe weather conditions. If we want to point out some of the advantages of using pre-treatment processes on a case-by-case basis, the following will be included:

Helps to have a continuous and reliable water flow
Increases the lifespan of reverse osmosis membranes used in later stages
Ensures standard quality of water sent to reverse osmosis or electrodeionization process
Increases the life cycle of general treatment plant processes and thus helps reduce final costs

Pre-Treatment Methodes

In general, wastewater in the local water supply system usually turns into a sludge form due to the presence of various raw tissue compositions. The pre-treatment process protects water and sewage transmission systems, including pipes, from hazards such as clogging and potential sediments.

Pre-treatment processes are classified into different types depending on the type and method or materials that will be removed in the end, but in general, pre-treatment processes in the water and wastewater industry can be divided into two general models:

Physical and Chemical processes (Physicochemical)
Biological processes
Physical and Chemical processes (Physicochemical)

Contaminated water usually has different suspended particles that are divided into four different categories based on size. Particles smaller than 0.08 micrometers are usually dissolved in wastewater, particles between 0.08 and 1 micrometer are colloidal particles, particles 1 to 100 millimeters in size are super colloid particles, and finally, particles larger than 100 micrometers are suspended in wastewater and can be deposited if at rest.

We will need physical and chemical processes to separate such particles. At this stage, colloidal particles are usually removed from the wastewater. Some perceptible particles can be removed by simple physical processes, but colloidal particles that are simply not visible to the naked eye are removed from the wastewater by a physicochemical process. For this purpose, various chemicals such as coagulants are used. These substances are added to the affluent and cause the physical state of the colloidal particles to change and form sedimentable colloidal clots by sticking together. Eventually, the particles that settle will be easily separated from the wastewater. In the physical and chemical pretreatment stage, the use of membranes is considered the most common method.

Zirsakht Tadbir Arian (ZETA) Company also pre-treats wastewater at this stage using the best and latest membrane separation and filter technologies. Softening silica removal (silicon dioxide, a common compound in rocks, sand, and mineral grains) with the help of up-to-date equipment is another service of this company. In general, the pre-purification services of ZETA Company are composed of two main parts in order to apply the pre-purification process. These two parts are filtration and separation and removal of silica. Various methods are used to remove silica from the wastewater composition, including ion exchange removal, softening by factors such as lime, reverse osmosis, ultrafiltration, and electrical coagulation.

Chemical Water Treatment Process

Softening Silica Removal

The method of softening and then separating silica is one of the common methods of removing it from the effluent, which is also used by Zirsakht Tadbir Arian (ZETA)Company. This method usually uses agents such as lime (calcium hydroxide) to remove or reduce the hardness of water by precipitating hardeners such as magnesium carbonate and calcium carbonate. After the addition of effective agents, silica is usually absorbed into the structure of calcium hydroxide and magnesium hydroxide and forms a bulk. The bulk is then separated from the effluent by a membrane or various filters. Depending on the concentration of silica in the wastewater, the amount of additives to it also changes, and the team of engineers at ZETA Company, taking advantage of up-to-date knowledge and appropriate equipment, undertake all the steps of silica removal.

Physical Water Treatment Process

Filtration

The method of softening and then separating silica is one of the common methods of removing it from the effluent, which is also used by Zirsakht Tadbir Arian (ZETA) Company. This method usually uses agents such as lime (calcium hydroxide) to remove or reduce the hardness of water by precipitating hardeners such as magnesium carbonate and calcium carbonate. After the addition of effective agents, silica is usually absorbed into the structure of calcium hydroxide and magnesium hydroxide and forms a bulk. The bulk is then separated from the effluent by a membrane or various filters. Depending on the concentration of silica in the wastewater, the amount of additives to it also changes, and the team of engineers at ZETA Company, taking advantage of up-to-date knowledge and appropriate equipment, undertake all the steps of silica removal.

Different types of membranes: 

Direct filtration is the separation by means of a tubular membrane and the ultrafiltration process by applying high pressure to the filtered fluid. The tubular membranes used in this process are resistant to various types of sediments and prevent possible clogging of the piping and water supply system. On the other hand, a side stream filtration is actually a form of filtration that is based on two different models:

Although less energy is consumed in the immersed method than in the side stream method, one of the important advantages of the side stream method is that in processes where the wastewater has a high velocity or flow rate, this model of membrane requires a lower surface to perform operations and it could lead to lower costs for the maintenance. In addition to the above, wastewater with a high concentration of solids is separated with the help of sidestream method with higher efficiency.

Biological Water Treatment Process

Filtration

Another type of pre-treatment process occurs at the stage of biological processes. During such processes, in fact, the purpose of separation is the decomposition of organic matter in wastewater with the help of natural processes and is planned based on biological science and biochemistry. The biological pre-treatment process relies on the decomposition of organic waste by bacteria, nematodes (tapeworms), and other small organisms through cellular reactions. Sewage usually contains a bulk of organic matter such as garbage, waste, and semi-digested foods, and may sometimes contain pathogenic organisms, heavy metals, and various toxins. Biological processes are usually considered to be more common than other methods due to their lower cost. These processes are usually divided into two general categories, aerobic and anaerobic. It is clear that in aerobic processes, the decomposition of organic waste material is done by living organisms in the presence of oxygen, but in anaerobic processes in the absence of oxygen.

Different biological processes in the pre-treatment stage will be different depending on the type of wastewater, but the main and basic stages and processes that are also provided by Zirsakht Tadbir Arian (ZETA) Company are as follows:

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