Objectives of Wastewater Treatment:
To kill the pathogens
To improve the quality of wastewater
To avoid unhygienic conditions
To protect the aquatic life from the toxicity wastes
To make the wastewater usable for agricultural, aquaculture etc.
There are three constituents and interrelated aspects of waste water management.
Collection of wastewater
Treatment of wastewater
Re-use of wastewater (Recycling of wastewater)
Performance criteria for Wastewater Treatment Management System:
The ideal system would satisfy all of the following criteria.
Pathogenic organisms should not be spread either by direct contact with right soil or sewage or indirectly via soil, water or food. The treatment chosen should achieve a high degree of pathogen destruction.
The treatment process should yield a safe product for re-use, preferably in aquaculture and agriculture.
In those cases land the should be considered exception when the waste cannot be re-use, the discharge of effluent into a surface water should not exceed the self-purification capacity of the recipient water.
The degree of odor release must be below the nuisance threshold. No part of the system should become aesthetically offensive.
The methods chosen for waste collection, treatment and re-use should be compatible with local habits and social (religious) practice.
The skills required for the routine operation and maintenance of the system components must be available locally or are such that they can be acquired with only minimum training.
Capital and running costs must not exceed the community’s ability to pay. The financial return from re-use schemes is an important factor is an important factor in this regard.
However, no one system completely satisfies all these demands. The problem becomes one of minimizing disadvantages.
Waste Water treatment Processes:
Municipal wastewater is primarily organic in content and a significant number of industries including chemical pharmaceutical and food have high organic waste load. This means that the main treatment processes are geared towards organic removal. In a typical treatment plant, the wastewater is directed through a series of physical, chemical and biological processes each with specific waste load reduction task. The tasks are typically.
Pre-treatment ==> Physical and / or chemical
Primary treatment ==> Physical
Secondary treatment ==> Biological
Advanced treatment ==> Physical and / or chemical and / or biological.
Conventional Wastewater Treatment Plant Processes:
Conventional treatment or conventional mechanical wastewater treatment is the term used to describe the standard method of treatment designed to remove organic matter and solid from solution. It comprises four stages of treatment.
Preliminary treatment ( influent flow measurement, screening (Bar racks), Shredders, comminutors (maceratours), pumping, grit removal)
Primary treatment (sedimentation)
Secondary treatment (biofitration or activated sludge)
Sludge treatment (anaerobic digestion of the sludge produced in primary and biological treatment)