All Clear with Leather and Training Agent

Efficiency up in water treatment over several levels of the automation pyramid in Mexico

The "Champion City for Water" is what León in Mexico has been entitled to call itself since the World Water Forum 2012. The industrial city received this honour in the category "Wastewater treatment". This is in no small part due to the plant builder and operator Fypasa with its treatment plant for tannery wastewater in León. Festo project engineers ensured the efficiency and reliability of the plant, which operates over several levels of the automation pyramid.

Léon, an industrial city 400 kilometres north of Mexico City with approximately one million inhabitants, is considered to be the world capital of leather and shoes. Countless world brands such as Adidas, Nike and Caterpillar have their products made in 600 tanneries and 1,000 shoe and leather factories, generating tons of wastewater. Tannery wastewater requires special treatment: beside organic tanning agents, the wastewater from the factories may also contain salts and metals such as chrome, zirconium, aluminium, titanium and iron, together with synthetic tanning agents such as formaldehyde and phenols.

Complete automation pyramid

The wastewater treatment plant which Fypasa built in 2009 and has operated ever since, supplements a treatment plant for household wastewater. The latter was previously also used for tannery wastewater but in the long term proved insufficient for the needs of the developing industrial city. Fypasa has been building and operating wastewater treatment plants throughout Mexico since 1969 and therefore has a great deal of experience as a plant builder. As a plant operator, the company treats 40% of all the wastewater in Mexico. "But as we are not specialists in plant automation, we rely on the experience of Festo's project engineers," explains Mauricio Plascencia, Operations Manager of the Fypasa treatment plant in León.

Festo developed a complete solution covering everything from the sensor/actuator level through to the field level, the individual control level and the process control level, including a SCADA process visualization system. Festo thus made things as easy as possible for Fypasa throughout the project value chain. 

Automation competence

"Starting with the engineering phase, we supplied Fypasa with a suitable automation concept, including circuit diagrams, CAD data and 3D models of the process valves and control cabinets, the central components of the sensor/actuator and field levels, so that they could be included in the designs as ready-to-install units," says Eduardo Poupard, Project Engineer with Festo Mexico. Festo was able to demonstrate that it had sufficient experience, based on many other projects in the field of water and wastewater treatment, and a good understanding of the processes involved in a wastewater treatment plant to develop a solution which meshed perfectly with the plant design.

The purchasing phase was completed efficiently thanks to the project management provided by Festo engineers, with activity charts, definitions of milestones and the punctual delivery of subsystems. The installation phase was simplified with simulation tests of the process valves and the control cabinets in the Festo Test Centre, the product documentation which Festo supplied and the installation of subsystems throughout the plant. "This made it easy for us at Fypasa to concentrate fully on our core competencies," continues Plascencia. During the commissioning phase, the Festo project engineers conducted process tests for each unit within the plant. For example, the operation of the process valves and the collection of fermentation gas was tested at the fermentation tower. 

From the master PLC to process actuators

At the individual control and process control level, the master controller PLC CECX-X-C1 from Festo acts as a programmable logic controller. It feeds data to the SCADA software VipWin to allow process visualization. CPX/MPA valve terminals gather the input and output signals, feed these to the master PLC and activate the pneumatic actuators. These are installed in seven control cabinets for protection. The automation platform CPX also provides functions for remote maintenance, remote diagnostics, a web server, text messages and an e-mail alarm.

The two fermentation towers are equipped with two types of process valves: gate valves for the sludge inlet and butterfly valves for the fermentation gas discharge. The pneumatic actuators used at the sensor/actuator level to open and close the process valves have significant advantages over electrical installations: durability, long service intervals and safety under overload conditions.

Security through process visualization

This holistic system approach, including process visualization, offers the plant operator greater transparency and thus more simplicity in the operating phase. What is more, because of the intrinsic simplicity of pneumatics the system is easier to maintain, saves costs and increases efficiency as staff require little training to work with the pneumatic system. The result is increased plant availability and efficiency. This will help ensure that in future the city of León will continue to earn its title of "Champion City for Water".

www.fypasa.com.mx

www.festo.com/water