The type and level of treatment to be applied to wastewater, which can be STP tank cleaning services or ETP tank cleaning services, depends on several factors, including the quantity and quality of the effluents.

In choosing the best treatment for wastewater it is also important to define the characteristics of the discharge site, as well as the level of water demand that varies depending on your destination.

Industrial waters have different physical and chemical characteristics from domestic effluents, so it is imperative to choose the most appropriate treatment as ETP tank cleaning.

The objective is to treat the waters so that they can be returned to nature and in conditions that are environmentally safe.

The effluent treatment is carried out in a Wastewater Treatment Plant and comprises four phases.

  • Preliminary treatment
  • Primary treatment
  • Secondary treatment
  • Tertiary treatment


This wastewater treatment process also includes the drying of sludge that has the potential to be used as fertilizers or even in the production of energy.

Major Type Of Wastewater

The source of wastewater allows it to be separated into three major groups: domestic wastewater, industrial wastewater. They have different characteristics and polluting loads, so they need different treatments.

  • Domestic Wastewaters: these effluents result from the use of water by the population and other housing activities, which may include wastewater from hotel and restaurant establishments. Sewage tank cleaning is suitable for this type of wastewater’s treatment.
  • Industrial Wastewaters: they come from discharges from different industries. Depending on the industry in question, the type of effluent varies. Wastewater from livestock, for example, needs to be treated differently from the effluents of an industry that uses chemicals.

Types of Wastewater Treatment for Industrial and Domestic Plants

The water plants are units for the processing and purification of effluents, whether of domestic or industrial origin. These waters are subjected to specific treatments and according to the initial characteristics of the effluent to be treated.

The final result must be in accordance with the parameters allowed for discharges into a water line or infiltration into the soil.

As previously mentioned, the treatment process comprises 4 phases, that is, the effluents are subjected to successive purification and disinfection phases:

  1. Preliminary Treatment / Pre-treatment

This phase comprises a set of physical processes, including the filtration of the coarsest residues, sediments and floating residues. This cleaning is carried out by harrowing, grinding and degreasing.

  • Screening: separation of larger solids through manual or automatic screening;
  • Desarenation: removal of sands and other solid mineral debris;
  • Degreasing: removal of grease from effluents.
  1. Primary TreatmentThe primary treatment can also be called physical-chemical treatment. The physical processes involve decanting by sedimenting particles, in order to remove fats and sands. The chemical processes are designed to correct the pH of the wastewater, as well as the coagulation and flocculation that will make the sediments larger and heavier, facilitating their decantation.
  2. Secondary TreatmentThis phase involves a biological process that aims to reduce the organic loads of the effluents. Through the activity of microorganisms, namely aerobic bacteria (whose activity depends on the presence of oxygen) and / or anaerobic (do not require oxygen), the degradation of the organic compounds resulting from the previous phase is carried out.

    In this phase, the almost total removal of the polluting load is achieved, namely:

  • Reduction of most of the total suspended solids (SST);
  • Reduction of chemical oxygen deficiency;
  • Depletion of biochemical oxygen demand.


This stage also requires a primary decanter to decant the primary sludge, an aerobic tank and a secondary decanter to decant the secondary sludge that may be re-circulated or subjected to processing

  1. Tertiary TreatmentIn this stage, a disinfection and nutrient control treatment is carried out. The goal is to get rid of bacteria and viruses. After this phase, the waters can be used for purposes such as agriculture, irrigation of green spaces, fire fighting, industrial processes, among other applications.
  2. Sludge TreatmentAt the end of these four phases, an effluent with a low level of pollution is obtained from ETP tank, on the one hand, and, on the other hand, various types of sludge from the previous stages.

It is recommended that these sludge be dehydrated and disinfected since, despite being rich in nutrients and organic matter, they can also contain pathogenic microorganisms. Its high moisture content also favors the growth of bacteria.

After disinfection and dehydration, these sludges can be used in agriculture as fertilizers, as a substrate for energy or even in the biofuels sector.

Objectives Of The Wastewater Treatment Process

Effluent treatment is designed to improve the quality of wastewater by eliminating:

  • Suspended solids.
  • Pathogenic bacteria and microorganisms.
  • Nutrients such as nitrate and phosphate, harmful to human health and enhancing the growth of unwanted algae creating an aquatic environment inappropriate for various species of fish.
  • Biodegradable natural products.

The main objective of treating domestic and industrial effluents is to eliminate waste in such a way that it does not endanger public health or the environment.

This process also has the advantage of producing sludge that can be applied in soil fertilization, energy recovery, fuels, among other uses.

Returning wastewater to the untreated environment endangers the health of people and the entire ecosystem, in addition to being considered a transgression, since the discharge of effluents is subject to legislation.