Simplified Method for the Determination of Total Kjeldahl Nitrogen in Wastewater

Abstract

The increase in total Kjeldahl nitrogen (TKN) concentrations is correlated with increases in cyanobacterial bloom biomass. Standard methods for the measurement of TKN are tedious, costly, time-consuming and involve the use of hazardous catalysts, such as mercury, high temperatures and significant amounts of toxic acids and bases. Since TKN plays a pivotal role in influencing algal blooms, there is an urgent need to develop simpler, safer and more accurate methods for the determination of TKN. The simplified TKN method (s-TKN™) developed by Hach® offers several advantages over the traditional TKN method, including eliminating the use of mercury, requiring low sample and reagent volumes and being cost-efficient and user-friendly. This communication presents preliminary results comparing the efficacy of s-TKN™ and the standard method, using commonly used primary standards and waste, estuarine and lake water matrices. For all primary standards analyzed, the s-TKN™ method exhibited good accuracy across a wide range of concentrations. The repeatability for the glycine–para-toluene sulfonic acid (Gly-PTSA) standard using the s-TKN™ method was 4.1% at the highest concentrations analyzed, with overall repeatability across concentrations comparable to the standard EPA method. For wastewater, estuarine and lake matrices, a good correlation (r2 = 0.9917) between the two methods and no statistical difference in the values (p > 0.05) were obtained between two methods. Preliminary studies indicate that the s-TKN™ method has the potential to reduce the expenditure associated with the cost of analysis and has the potential to be a safer and cheaper alternative, while providing comparable analytical results to the standard method.

Keywords

• total Kjeldahl nitrogen (TKN)
• wastewater
• nitrates
• inorganic nitrogen
• total nitrogen
• organic nitrogen