**2. Objective and specifications**

Following the flow chart design process described in Fig. 2, the objective and the specification of the system are defined in this section.

The objective of the control system is to improve efficiency and quality of the whole process of purification in two aspects:

a. On the one hand it involves a study of the process restructuring it or modifying those steps or elements deemed inefficient.

Expert System Design for Sewage Treatment Plant 67

With reference to the development of the operative part of the system, it is necessary to do

As to the first point, the process of purification consists of the following processes: Filtering, elimination of the colloids through the process physical-chemical clotting and flocculation, treatment to regulate the Ph of the water, biological treatment and finally, decanting and

Fig. 4. Procedure for building an expert system

1. Description plant and process control. 2. Selection and sizing of components

two basic aspects:

b. In the other hand it provides continuous monitoring of sewage treatment. Also displays historical process data and manage the process notices provided by the system. This not only allows real time monitoring of the plant but also to make predictions or future prospects.

There is a relationship between the different elements of the control system SCADA and the work they do within the system. With these automated systems achieve optimize sewage treatment with comparison of actual and theoretical graphics. Modification of the existing situation assumptions are made and are valued, quantifying their effects to the objectives set. Therefore, the objective of operation of the plant is granted.

From a technological perspective, the following requirements for the development of the system control have been established:


On the basis of these requirements, and prioritizing the relation cost-versatility, for the implementation of the system the following were chosen:


Fig. 3. Human-machine interface
