Abstract
Four granular sequencing batch reactors (GSBRs) were inoculated with four denitrifying Pseudomonas strains carrying nosZ to study the process of granule formation, the operational conditions of the bioreactors, and the carbon concentration needed for nitrate removal. The selected Pseudomonas strains were P. stutzeri I1, P. fluorescens 376, P. denitrificans Z1, and P. fluorescens PSC26, previously reported as denitrifying microorganisms carrying the nosZ gene. Pseudomonas denitrificans Z1 produced fluffy, low-density granules, with a decantation speed below 10 m h−1. However, P. fluorescens PSC26, P. stutzeri I1, and P. fluorescens 376 formed stable granules, with mean size from 7 to 15 mm, related to the strain and carbon concentration. P. stutzeri I1 and P. fluorescens 376 removed nitrate efficiently with a ratio in the range of 96%, depending on the source and concentration of organic matter. Therefore, the findings suggest that the inoculation of GSBR systems with denitrifying strains of Pseudomonas spp. containing the nosZ gene enables the formation of stable granules, the efficient removal of nitrate, and the transformation of nitrate into nitrogen gas, a result of considerable environmental interest to avoid the generation of nitrous oxide.
Highlights
PSC26 were provided by the Zaidin Experimental Station (CSIC-Granada), P. fluorescens 376 was provided by the Water Research Institute Culture Collection (University of Granada), and P. denitrificans Z1 was supplied by the National Collection of Industrial, Food, and Marine Bacteria (NCIMB) (NC012776) [26,27,28]
The aerobic granular technology inoculated with denitrifying bacteria showed a success nitrate removal ratio. which depends on the carbon concentration added to the influent
The findings showed that denitrifying Pseudomonas strains are able to produce stable granules in granular sequencing batch reactors (GSBRs) systems. resulting in high nitrate removal
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A large proportion of the world’s population uses groundwater as a drinking water resource, so the quality of groundwater and the removal of any pollutants is of paramount importance worldwide. The increase in the use of chemical compounds such as fertilizers, pesticides, pharmaceuticals, and personal care products is responsible for extensive groundwater pollution. Nitrate is one of the most widespread pollutants in groundwater due to the intensive use of fertilizers in agriculture, resulting in the joint release of nitrate and phosphate ions [1]. Excess nitrate can be released to aquatic environments because it is highly soluble and mobile, which affects the quality of water [2]
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