Ammonia removal in a deep reclaimed wastewater reservoir before agricultural reuse

An experimental study has been carried out to determine the ammonia removal in a deep reclaimed wastewater reservoir of 50,000 m3. The reservoir is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain). The study has been conducted under batch mode operation, in three different periods (winter, spring-summer and winter-spring), with an average storage time of 85 days. Vertical profiles of temperature, dissolved oxygen and pH were determined together with NH₃-N, NO₂-N and NO₃-N concentrations at different points and different depths in the reservoir. Maximum removal efficiency was obtained during the winter periods, in absence of stratification and with good mixing conditions throughout the water column. During these periods, nitrification took place in some extension, favoring the ammonia removal. Average NH₃-N concentrations in the reservoir were calculated and apparent first-order rate constants were determined for different stratification conditions. Although ammonia nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for disinfection.