Nitrate removal from drinking water in a packed‐bed bioreactor coupled by a methanol‐based electrochemical gas generator

Abstract

Removal of nitrate from drinking water by a coupling of methanol-based electrochemical hydrogen and carbon dioxide generator and a packed-bed bioreactor was investigated. The major goal was to study the performance of this integrated system for simultaneous, economical, in situ, and on-demand electron donor and carbon source production for hydrogenotrophic denitrification of drinking water in actual scales. The ability of system has been evaluated for treatment of natural underground water up to 120 mg NO 3 2 /L (threefold of the drinking water limit) nitrate concentration. Removal efficiencies above 95% were achieved for more than 150 days of operation at a 2-5 h retention time. Furthermore, the system was operated only by injection of two harmless gases (produced by electrolysis of methanol) and without any chemical addition (solid or liquid). In the electrolysis process, H 2 and CO 2 (H 2 as an electron donor and CO 2 as a carbon source for denitrifier bacteria) was produced cheaply and simultaneously by applying a very low DC voltage (4-6 V) to a solution that includes an easily oxidizable organic substance (methanol) and electrolyte solution comprised water and a base. In situ and under control generation of H 2 and CO 2 by an efficient, cost-effective way showed that this process can be an acceptable and reliable system for treatment of nitrate contaminated drinking water in actual scales. Additionally, convenient process operation without need of high pressure and explosive gas cylinders and only by voltage adjustment is other advantage of the process.

Chemolithotrophic denitrification in biofilm reactors

“…Water electrolysis [39][40][41][42][43] and anoxic corrosion of metallic iron [44] are among the most used methods for hydrogen production in PBRs. Methanol electrolysis, producing both H 2 and CO 2, was coupled to autotrophic denitrification in a PBR operated by Vagheei et al [45]. Nitrate removal efficiencies above 95% and removal rates up to 0.339 kg N-NO 3 À /m 3 d were achieved at HRTs ranging from 2 to 5 h.…”

Hydrogenotrophic denitrification of potable water: A review

“…Grommen et al [21] generated hydrogen gas with a two-compartment electrolytic cell containing two plain perforated nickel electrodes, while hydrogen was supplied through the top of the reactor. Vagheei et al [108] produced in situ hydrogen and carbon dioxide by the electrolysis of methanol. Fixed-bed reactors were used in which gas entered from the bottom of the reactor.…”

Preparation and application of a surfactant‐modified Halloysite nanotubes for the adsorption of nitrates from aqueous solutions: Kinetic and equilibrium studies

“…Water pollution is the main problem in our world today and, is a major hazard that causes many problems to the people and environment 1–3 . It is widely recognized that the most principal source of water contamination worldwide is nitrate 4–6 . Drinking water that contain more than 50 mg/L nitrate ions resulted in various human health issues such as blue‐baby syndrome 7 .…”