Low cost-sensors as a real alternative to on-line nitrogen analysers in continuous systems

摘要

This paper is focused on the evaluation of the applicability of low-cost sensors (pH and ORP)nversus nutrient analysers for controlling biological nitrogen removal in WWTPs. A nutrient removalnpilot plant located in Carraixet WWTP (Valencia, Spain) that is equipped with a significant numbernof nutrient analysers and low-cost sensors was used. The relations between reliable, cheapnon-line sensors such as pH and ORP (located in anaerobic, anoxic and aerobic zones) and thennitrification/denitrification processes are provided. The nitrification process can be evaluated bynmeasuring the pH difference between the first and last aerobic zones. The denitrification processncan be evaluated by measuring the pH difference between the first and last anoxic zones and thenORP in the last anoxic zone. Furthermore, when WWTPs include an anaerobic reactor, the ORP innthe anaerobic zone can also be used. With all these factors in mind, these sensors give valuableninformation for applying advanced control systems such as fuzzy logic-based controllers. Also,nlow-cost sensors involve lower investment, maintenance and operational costs and lower energynconsumption derived from aeration and pumping than nutrient analysers. Thus, low-cost sensorsncan be successfully used as an attractive alternative to nutrient analysers to control biologicalnnitrogen removal in WWTPs.