Wastewater Treatment Factsheets
- Coarse Screens
- Grit Removal
- Biological Filters
- Activated Sludge – Overview
- Sludge Digestion – Overview
- Sludge Thickening and Handling
- Effluent Disinfection – Overview
Sewage passes through bar screens for removal of larger objects (rags, plastics, tins, wood, etc.) Automatic or manual bar screen cleaners remove the larger objects from the raw sewage. The collected material is temporarily stored to be transferred later to a landfill site.
The filter consists of an outer shell normally made of concrete. Under-drains on the floor of the filter allow for the collection of the effluent from the bottom of the filter and allow for the free passage of air through the filter, which is important, as the micro-organisms, which grow in a filter, require oxygen from the air to live.
Sludge digestion – Overview
In wastewater treatment considerable quantities of sludge are constantly being produced. In their raw state the sludge are putrescible and rapidly develop strong and obnoxious odours. Sludge also contain pathogenic (disease-causing) organisms harmful to man. It is therefore necessary to contain and treat these wastes.
Sludge Thickening and Handling
Thickening is the process used to increase the solids content of sludge by the separation and removal of a portion of the liquid phase. Gravity thickening makes use of the force of gravity as the main agent in the settling and thickening process.
The disinfection treatment process will remove or inactivate pathogenic micro-organisms. Not all organisms are killed during disinfection, as is the case with water sterilization. The purpose of disinfection is to kill or inactivate all the primary micro-organisms, such as bacteria, viruses and protozoan cysts.