Biological nitrate removal from groundwater by an aerobic granular technology to supply drinking water at pilot-scale

Groundwater Nitrate Removal Performance of Selected Pseudomonas Strains Carrying nosZ Gene in Aerobic Granular Sequential Batch Reactors

“…Chemical oxygen demand (COD) was measured following the standard spectrophotometric method described by APHA [32]. Biological oxygen demand at day 5 (BOD 5 ) was also measured using dark bottles and an OxiTop™ [3].…”

“…Some diseases, such as methemoglobinemia, thyroid disease, or neural tube defects, have been linked to the consumption of drinking water contaminated with nitrate [3]. Nitrite has been described as a carcinogenic agent [4,5].…”

“…The areas most affected by nitrate pollution are designated as nitrate vulnerable zones and are subject to the mandatory Code of Good Agricultural Practice [8]. The results of compliance with this directive have been reflected in the trends in nitrate levels in some countries, such as the northern regions of Europe [5], while the Mediterranean countries have experienced major difficulties in achieving the quality standard due to the strong pressure linked with intensive agriculture [3]. To exemplify this difficulty, in 2012, 108 Spanish municipalities reported having an average of 3.5 mg•L −1 NO 3 in the groundwater they used as a source of drinking water, with a concentration range of 0.4 to 66.8 mg•L −1 [9].…”

“…Given this background, the sanitary control of groundwater has become of special interest for governments. Therefore, in order to achieve the standard, several physical, chemical, and biological groundwater treatment technologies have been developed, amongst which we may highlight systems such as chemical reduction [10], electrodialysis [11], ion exchange [12], adsorption [13], reverse osmosis [14], biofilters [15], and aerobic granular technology [3]. Although ion exchange is a widely implemented technology for treating nitrate, when the resin is exhausted, the brine waste has negative environmental impacts [12].…”

“…However, the high hydraulic retention time directly affects the volume of groundwater treated and poses difficulties for cleaning the system, which can increase investment costs [15]. For these reasons, new low-cost and environmentally friendly technologies are gaining relevance, and in this context, a novel aerobic granular technology for treating nitrate-polluted groundwater was recently described [3].…”