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Understanding Activated Sludge Wastewater Management: A Process Overview

Activated sludge wastewater management systems are among the most commonly (and successfully) used wastewater systems today, but there is also a great variety within this method/system. At WEC Projects we are keenly aware of this fact, because experience has taught us that different clients and settings have different requirements for their method of wastewater management. The following steps represent one of the conventional approaches to activated sludge wastewater management:

Activated Sludge Wastewater Management

Step 1: Screening and grit removal

Before the wastewater can be effectively processed, as much solid waste matter as possible needs to be removed. This is predominantly managed through screening and related methods such as bar racks and grit chambers.

Step 2: Primary clarification

Once solid matter such as debris, sand and algae has been removed, the remaining wastewater can then be moved into the primary clarifier. In the primary clarifier the wastewater is managed by allowing the heavier organic sediments or suspended solids to settle to the bottom of the basin. Wastewater treatment companies (among other studies) have found that a retention/detention time of 2 to 3 hours should remove between 50% and 70% of the suspended solids (with an assumed removal of 60%).

Step 3: Aeration

Once the primary clarification is complete the wastewater is moved through to an aeration tank where it is mixed with the activated sludge. This mixture, known as the mixed liquor, is then aerated (agitated by a constant supply of bubbles) which stimulates the aerobic processes and increases the growth rate of bacteria. The increased growth of bacteria in the mixed liquor leads to flocculation, effectively gathering and clumping together more of the remaining solid matter and waste material in the water.

Step 4: Secondary clarification

After the aeration is complete the wastewater management process moves into the secondary clarifier. Here the flocculated materials sink to the bottom of the secondary clarifier as sediment, effectively removing the remainder of the solid waste material.

Step 5: Disinfection

In the secondary clarifier the sediment and remaining water are separated, and the water is treated further by filtration to remove the finer suspended solids. After that the water is disinfected to remove any remaining waste matter or dangerous organisms, producing a clean effluent.

Get the correct solution for your individual setting

As mentioned earlier, this process represents only one of the various variations available in activated sludge wastewater management. Contact WEC Projects to get the best advice and solutions for your specific water and wastewater management needs. We’ve been serving the African continent’s needs for years, and we will use this experience to your advantage.