TOC/TNb Determination in Pulp and Paper Process Effluents Applikationsschrift · multi N/C 2100S

Introduction

The pulp and paper industry generates large volumes of wastewater or effluents that need to be treated before they can be reused or released into natural waterways.

According to the European Industrial Emissions Directive (IED) Best Available Techniques (BAT) have to be implemented within the EU for direct wastewater discharges from pulp, paper and card production1). The BAT reference document (BREF) indicates that among other parameters, TOC (total organic carbon) and TNb (total bound nitrogen) are of growing importance. They need to be monitored on a daily or weekly basis. Furthermore, for economic and environmental reasons a preference for the parameter TOC instead of COD is given as it does not require the use of highly toxic compounds like dichromate (Cr VI) and mercury.

In many cases the COD and TN contents are still measured using separate methods. This is a labour and time consuming process and associated with the formation of chromium VI and mercury contaminated waste. By correlation studies an empirical conversion factor for TOC (total organic carbon) to COD conversion can be established for specific emission sources and waste water treatment steps. This allows a fully automated analysis process for TOC/TNb determination according to EN 1484 and EN 12260 (as well as the planned new ISO 20236 for both parameters) to be applied, which saves resources and time.

Since process effluents from pulp and paper production often contain a large amount of solids (cellulose fibers), direct injection technology has proven particularly effective for TOC/TNb analysis. The multi N/C 2100S does not require hoses or valve technology, but doses the sample directly into the combustion chamber via a septum-free injection port and a wide bore needle using a microliter syringe. The direct injection technique provides a safe and reproducible particle transfer without the risk of clogging or carryover. This increases instrument availability, reduces wear and tear and increases sample throughput and efficiency.