Pretreatment in WWTP's

Importance of Pretreatment in WWTP and Pumping Applications

The pretreatment in WWTP’s consists of certain processes carried out before the main treatment to prepare the water to facilitate subsequent processes, and even to protect equipment’s installed downstream. The most common pretreatments are degreasing, sand removal and screening. Let’s understand a little more about each one:

1- Screening: it is the operation of separating solid material from the wastewater through mechanisms that work with the principle of the strainer. Its main objective is to remove material such as cans, plastic packings, etc., which could affect negatively the correct operation of pumps or aerators installed downstream. The most used are static screens and screens with cage shape. Nowadays, there are mechanized systems such as rotating and self-cleaning screens.

2- Sand removal: consists of separating the sand from the process water. The sand can generate damage due to wear in pumps and aerators. The most common method to remove the sand is by designing long channels with laminar flow so that the sand settles and does not escape. Nowadays we have technology available to pump the sand out from the holding tanks.

3- Degreasing: it consists of the separation of fats and oils from the process water. The grease acts as a biological activity inhibitor and must be eliminated. Since the fat and oil have a lower density than water, it will be located at the top; therefore, the typical way to eliminate it is to design the tank to trap the grease on the top and then allow the operator to remove it manually. Nowadays, this kind of systems can incorporate automatic scrapers to separate the grease and pour it into attached tanks.

Pretreatment is one of the most important and essential processes within a WWTP. We have technology and various pretreatment alternatives according the flow, solids to be handle, and type of process. Some of these products include stainless steel holding baskets, stainless steel screens, self-cleaning screens, rotating screens, solid-liquid separators, grease separators for wastewater facilities, and sand separation systems. For more information, contact us to

Image from EMO Environment by Technology (2016) Seminar in pretreatment and sludge treatment. Rennes.