Treatment and disposal of wastewater
The responsibility for treatment and disposal of wastewater falls on the 10 privatised water companies in England and Wales and the Regional Councils in Scotland.
The National Rivers Authority (NRA), which functions under the DoE, is the body responsible for setting and monitoring effluent discharge standards for wastewater treatment works in
the UK.
Single standards are still applied in many European countries, but the UK now bases its consent standards on environmental quality standards. The quality required in the watercourse, depending on the use it is put to is defined. This is known as the “River Quality Objective”(RQO), on the basis of this and the dilution available, the discharge standard known as the “Objective Standard” is set. These standards are presently being further tightened with the introduction of new EC Directives which are implemented by means of UK legislation.
Estimation of design loads for biological process design is difficult because domestic loads vary greatly from one country to another for various reasons, such as the use of domestic waste disposal units and differences in personal hygiene practices.
The general concept of design is to establish the combination of unit processes in the right sequence such that each may; operate at optimum efficiency, produce the required product, achieve the lowest capital and operating cost, and maximise the return of the capital invested. The design comprises of three main steps in the form of; Process design, Functional design and Detailed design; in selecting a suitable sequence of unit processes, estimation of capacities and the structural design of units