Phosphorus limitation in nitrifying groundwater filters

• Published in: Water research (Oxford) 2012-03, Vol.46 (4), p.1061-1069
• Main Authors: de Vet, W.W.J.M., van Loosdrecht, M.C.M., Rietveld, L.C.
• Format: Article
• Language: English
• Subjects: adenosine triphosphate; Adenosine Triphosphate - analysis; ammonia; Applied sciences; ATP; Batch Cell Culture Techniques; bioassays; cell growth; denitrifying bacteria; drinking water; Drinking Water - microbiology; Drinking water production; Exact sciences and technology; filters; Filtration - instrumentation; genes; Groundwater; Groundwater - microbiology; inoculum; iron; Iron removal; microbial growth; Microbially available phosphorus; mixed culture; Netherlands; nitrates; Nitrates - analysis; Nitrification; Nitrites - analysis; orthophosphates; Oxidation-Reduction; Phosphates - analysis; phosphoric acid; phosphorus; Phosphorus - analysis; Pollution; Pseudomonas fluorescens - metabolism; quantitative polymerase chain reaction; Quaternary Ammonium Compounds - metabolism; Reference Standards; surface water; temperature; water treatment; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2011.11.075

Phosphorus limitation has been demonstrated for heterotrophic growth in groundwater, in drinking water production and distribution systems, and for nitrification of surface water treatment at low temperatures. In this study, phosphorus limitation was tested, in the Netherlands, for nitrification of anaerobic groundwater rich in iron, ammonium and orthophosphate. The bioassay method developed by Lehtola et al. (1999) was adapted to determine the microbially available phosphorus (MAP) for nitrification. In standardized batch experiments with an enriched mixed culture inoculum, the formation of nitrite and nitrate and ATP and the growth of ammonia-oxidizing bacteria (AOB; as indicated by qPCR targeting the amoA-coding gene) were determined for MAP concentrations between 0 and 100 μg PO 4–P L −1. The nitrification and microbial growth rates were limited at under 100 μg PO 4–P L −1 and virtually stopped at under 10 μg PO 4–P L −1. In the range between 10 and 50 μg PO 4–P L −1, a linear relationship was found between MAP and the maximum nitrification rate. AOB cell growth and ATP formation were proportional to the total ammonia oxidized. Contrary to Lehtola et al. (1999), biological growth was very slow for MAP concentrations less than 25 μg PO 4–P L −1. No full conversion nor maximum cell numbers were reached within 19 days. In full-scale groundwater filters, most of the orthophosphate was removed alongside with iron. The remaining orthophosphate appeared to have only limited availability for microbial growth and activity. In some groundwater filters, nitrification was almost totally prevented by limitation of MAP. In batch experiments with filtrate water from these filters, the nitrification process could be effectively stimulated by adding phosphoric acid. ► Nitrifiers have lower affinity for phosphorus than heterotrophic bacteria. ► Strongly reduced nitrifiers’ growth rate at phosphorus under 50 ppb. ► Groundwater nitrification hampered by limitation of available phosphorus.