|Simple Waste water Treatment Process Diagram.|
Procedure of Waste-water Treatment Plant
The following is the step by step process for treating the waste water
Step 1- Waste Water Collection.
Step 2- Odour Control.
Step 3 - Screening.
- Coarse screen has larger openings from 75- 150 mm.
- Medium screens has opening from 20-50mm.
- Fine screens have openings less than 20mm.
Grit Chamber- The waste water is then passed through grit chamber where the inorganic materials like sand, ash etc are removed. Basically the sedimentation process is been carried out in this part.
Skimming Tanks- There are chances of having greasy and oily elements in waste water from industries and manufacturing firm outlets. Thus skimming tanks helps to remove this unwanted materials form waste water. The skimming tank is surrounded by baffle walls and the compressed air is been flushed inside from the floor of skimming walls and the rising air bubbles coagulates and solidify these materials and these material are then pushed to side compartment from where these elements are easily removed.
Step 4- Primary Treatment.
then this matter gets settled down due to action of gravity after a certain amount of time. Sometimes the coagulants are used to facilitate the sedimentation process & then this process is called as coagulation- aided sedimentation.
The process of sedimentation depends upon some factors like size, shape & specific gravity of particles besides viscosity and flow velocity of waste-water. In normal process of treatment, sedimentation is usually carried out twice-once before the secondary treatment, referred to as primary sedimentation and after this process the secondary sedimentation is brought to action.
Coagulants: These are chemicals usually positively charged & which form insoluble & gelatinous precipitates with colloidal particles which are negatively charged which are present in waste water and thus this particles become denser and due to gravity action they gets settled down at bottom of sedimentation tank. The most common used coagulants in treatment process are alum (aluminium sulphate), iron salts (ferric sulphate, ferric chloride), lime and soda ash (sodium carbonate), sodium silicate & sodium aluminate.
Step 5- Secondary Treatment.
- Activated Sludge - It is the process of treating sewage and industrial waste waters using air and biological floc composed of bacteria and protozoa.
- Aerated Lagoon - It is a holding or treatment pond provided with artificial aeration to promote the biological oxidation of waste water. There are many other biological process for waste water treatment for example trickling filters, rotating biological contactors & biofilters.
- Aerobic Granulation - The biological waste water treatment is often accomplished using conventional activated sludge systems. These systems generally require large surface area for treatments and biomass separation units due to generally poor settling properties of the sludge.