TOC and TN Measurements of Wastewater

Introduction

TOC (total organic carbon) measurement can be performed in a shorter time with a good repeatability compared to BOD (biochemical oxygen demand) and COD (chemical oxygen demand) measurements, and is used as an index for organic pollutants which indicate the degree of water pollution. Since a TOC analyzer directly measures the amount of carbon comprising organic substances, it is less likely to be influenced by sample matrices. Consequently, this is used in a variety of fields, from control of raw factory wastewater containing salts, control of treated wastewater and effluent water, and to the monitoring of the organic matter content in drinking water, environmental water, purified water, etc. In particular, since factory wastewater and influent water which flows into effluent treatment facilities contain high amounts of organic contaminants, TOC control is necessary to optimize the running condition of such facilities. TN (total nitrogen) is also important as a substance that causes eutrophication, and stipulation of its drainage criterion indicates that it is regarded as a point of importance for wastewater control to prevent environmental pollution. Sewage contains a high content of ammonium nitrogen, and wastewater of a factory which uses nitrogen compounds for materials or additives still contains nitrogen compounds even after treatment. Therefore, the TN concentration in effluents must be controlled to reduce environmental burdens. Shimadzu TOC-L total organic carbon analyzer can be used for simultaneous measurement of TOC and TN by installing the TNM-L total nitrogen unit. When measuring nitrogen content using the Kjeldahl method, multiple reagents such as acids and alkalis are required and the measurement takes several hours for digestion and distillation. The TNM-L, on the other hand, uses the thermal decomposition - chemiluminescence method which is no need for reagents and measurement results can be obtained rapidly since each measurement takes only approx. five minutes. Furthermore, the TOC-L has an automatic dilution function to dilute raw wastewater samples before measurement; the function contributes to reducing the frequency of replacements of consumables, such as the catalyst and combustion tubes. This application news introduces an example of simultaneous measurements of the TOC and TN of wastewater from a metal plating factory and its treated wastewater, using Shimadzu TOC-LCPH total organic carbon analyzer and TNM-L total nitrogen unit.

November 21, 2017 GMT