Sedimentation on waste treatment plays an important role. Sedimentation is a process which aims to separate solids from a liquid so that the liquid is free of solids based on the principle of gravity. This is important because water discharged into the environment should not contain solids according to the established quality standard (EPA, other local regulation). In addition, the presence of solids could cause further process disrupted.
The uses in sewage treatment include:
- Separation of sand, mud, gravel.
- Separation of suspended solids in initial sedimentation.
- Separation of microbial and medium collections from sedimentation of activated sludge
- Separation of humus.
The tools used in sewage treatment are mostly the same as the water treatment equipment because both have the same end goal; that is to produce clean water. The sedimentation tank or pool may have a long, circular, or square cross-section. Equipment that uses the sedimentation principle is usually called clarifier, thickener, sedimentation basin, or sedimentation basin.
In the waste processing, sedimentation is generally done twice. That is the initial sedimentation and the final sedimentation. The initial sedimentation aims to separate the solids present in liquids, including gravel, mud, and other suspended solids. These solids have the potential to disrupt the subsequent process. While the final sedimentation aims to separate the collection of microbes and their medium after experiencing biological processes.
In general, the sedimentation process consists of four types. These types are characteristic of the sedimentation process itself. The types are:
- Type I or free settling
Type I is the precipitation of a non-continuous solid and does not form a floc in a dilute suspension. In this type of particle precipitates as a separate part and there is no interaction between the particles. An example of this type is the deposition of sand particles in a settling basin.
- Type II or flocculant settling
Type II is the precipitation of the flocculant particles in a dilute suspension. The particles form a floc during the precipitation so that the particle will expand and settle at an increased rate. An example of this type is precipitation by adding flocculants.
- Type III or hindered settling
Type III is a precipitation with medium solids concentration so that the solids are close together. This will lead to interaction between solids so that there is a force that keeps the solids in a fixed position and ultimately settles at the same rate. This solid settle together as a zone and at the top of the zone, there is a clear boundary between clearer solids and liquids. An example of this type is the precipitation that occurs in the center of a clarifier.
- Type IV or compression settling
Type IV is the precipitation that occurs at high concentrations so that the solids will be in contact and the precipitation can only occur with compression and mass compaction. An example of this type is the precipitation that occurs at the bottom of the clarifier.