Dual redundancy control at Bratislava water works

A GE Fanuc Intelligent Platforms UK product story

Edited by the Engineeringtalk editorial team Jan 31, 2002

A new, automated sludge treatment infrastructure was commissioned at Petrzalka in Slovakia during 2000, using GE Fanuc's Cimplicity and OPC Server to provide dual redundancy control and supervision

The waste-water treatment plant serving the area of Bratislava-Petrzalka in Slovakia used to rely on transporting sludge residue by road for treatment in the main Bratislava water works.

A new, automated sludge treatment infrastructure was commissioned at Petrzalka during 2000, using GE Fanuc's Cimplicity and OPC Server to provide dual redundancy control and supervision of the total plant SCADA system.

Originally transported by tankers via the centre of Bratislava to its waste plant, the crude sludge is now treated at source, straight after separation at the Petrzalka works.

with K and H Kinetic a.s.

supplying and installing the electrical and control system technology.

The sludge undergoes a number of processes before dehydration.

Some of the energy used in the plant is reclaimed from the waste material.

First, the thickened sludge is moved to a holding basin, from which it is pumped in sequence to two 5000 m3 decay tanks.

Special deflectors in the base of these tanks help to optimise the flow of material through the system.

Heat treatment in the decay tanks encourages the anaerobic fermentation process which results in the release of bio-gas.

The control technology ensures that fermentation is carefully optimised by the heat exchanger to control the temperature at 39C.

It also ensures that the organic portion of the final dry stabilised sludge is below the 50% level.

The bio-gas which is captured is stored in a 2390 m3 double membrane gas holder.

This gas is burned in the bio-gas boiler room in three gas boilers, each of which produces 550kW of heat for use throughout the plant.

The heat is used, for example, to encourage the decay process.

After allowing for re-capture of the bio-gas, the sludge is removed to a storage tank.

Here it is homogenised by air pumped under pressure into the bottom of the tank.

The waste is then dehydrated in a separator.

A decantation and chemical management process takes place, handling 40 cubic metres/hour.

This increases the ratio of the dry content to above 30%.

A series of screw, chain and belt conveyors transport the dehydrated sludge into a large roofed storage area.

K and H Kinetic was appointed in 1999 to provide the instrumentation and control system and to install the electrical infrastructure.

GE Fanuc's Cimplicity software, operating on dual redundant PCs, was chosen to provide overall supervisory control of the SCADA system using 5 PLCs.

If one of the PCs fails, Cimplicity initiates the uninterrupted switch-over to the other PC.

K and H Kinetic developed the software applications including the user-friendly Cimplicity graphics screens that provide the operators with clear pictures of the functions throughout the plant.

An intermediate PLC collects analogue input data from throughout the plant, such as temperature, pH, dissolved oxygen levels and flow rates.

It also handles communications between the other 4 PLCs and the control room PC which runs under Cimplicity OPC Server.

OPC Server offers an open systems approach enabling the integration of Cimplicity HMI with other software applications.

The 4 PLCs handle the digital I/O enabling them to control the pumps, air compressors, conveyors, etc.

According to Ing.

Josef Rubas, General Manager of K and H Kinetic, "The use of Cimplicity has resulted in the very efficient use of the installed control technology.

The ability to react accurately and immediately to the changing conditions of the fermentation process, for example, has led to an improved production rate of bio-gas.

The production now far exceeds that needed for heating and the customer is planning to use the excess to generate electricity of up to 400kVA.

They will use this power to drive the compressors and pumps thus reducing their demand for the electricity which they currently buy in.".