In the spotlight | Lanxess - right river side

Project

Description

LANXESS is renowned for its specialty chemicals and active worldwide in the production of specialty chemicals, intermediates, plastics and synthetic rubber. At the plant in Lillo, Antwerp, LANXESS produces caprolactam and polyamide. The process plants of LANXESS generates various wastewater streams that are treated in the wastewater treatment plant.

Overview of part of the caprolactam complex

On the site, a distinction is made between non biologically treatable and curable organic industrial waste. The not biologically treatable wastewater undergoes a neutralization and sedimentation. The biologically treatable wastewater, including sanitary sewage of both companies, is treated in a biological water treatment plant. The biological wastewater treatment involves the following steps: neutralization, sedimentation, denitrification, aeration, sedimentation and sludge flotation. The cleaned waste water can be cooled, if necessary, on one or two parallel cooling towers in order to meet the imposed discharge temperature norm. The effluent is eventually discharged into the Scheldt.

The activated sludge continuously grows by the decomposition of organic material; in order to maintain a constant sludge content, therefore a portion of the return sludge is disposed of. In order to reduce the discharge cost this excess sludge is mechanically dewatered in a decanter centrifuge, in which it is thickened to about 20% dry matter. This centrifuge process is optimized by adding polyelectrolyte and ferric chloride to the excess sludge.

Realisation

On the Lillo site the polyamide plant was started in the summer of 2014. A study by Trevi indicated that additional aeration capacity of the biological treatment plant was required to meet the increasing emission standards.

To each of the existing parallel aeration basins a second aeration basin was connected in series, each with a capacity of 1500 m³ and put in service. The extra accomplished aeration capacity of 2 x 2125 Nm³/h means an additional COD-processing capacity of 7 tons per day. These aeration basins are equipped with energy-efficient fine bubble aerator plates produced by Trevi. The management and daily monitoring of the entire water treatment occurs in close cooperation with Trevi. Due to the expansion of the aeration basins a lower sludge load is obtained. As a result a lower residual concentration of organic components at the point of discharge are obtained and decreases the wastewater charge accordingly. In addition a better quality sludge is obtained with a positive effect on the separation of sludge and treated effluent. This results in a stable process control.

Detail aeration (air collector - aeration panels)