Aerated biological filtration process for water treatment with a view to reducing the nitrogen content (NGL) of said water with reduction of carbon-source and aeration requirements

A method of biologically treating untreated water containing carbon sources and nitrogenous pollutants and reducing a concentration of ammoniacal nitrogen (NH4+) in the treated water, the method comprising:

• splitting the untreated water into first and second untreated water streams;
• directing the first untreated water stream into a first aerated biological reactor and subjecting the first untreated water stream to nitritation and filtration;
• passing the first untreated water stream through the first aerated biological reactor where ammonium oxidizing bacteria (AOB) converts a portion of the ammoniacal nitrogen to nitrites;
• filtering the first untreated water stream passing through the first aerated biological reactor with filtering material contained in the first biological reactor to form a treated water stream;
• wherein the treated water stream leaving the first aerated biological reactor is rich in nitrites and includes some ammoniacal nitrogen and nitrates;
• mixing the treated water stream leaving the first aerated biological reactor with the second untreated water stream to form a third water stream containing the carbon sources of the second untreated water stream;
• directing the third water stream into a second non-aerated biological reactor and subjecting the third water stream to deammonification, denitrification and filtration in the second non-aerated biological reactor;
• in the second non-aerated biological reactor, contacting the third water stream with media having anammox bacteria and heterotrophic bacteria supported thereon;
• wherein through an anammox reaction, the anammox bacteria in the second non-aerated biological reactor, via deammonification, converts ammoniacal nitrogen and nitrites in the second non-aerated biological reactor;
• wherein the heterotrophic bacteria in the second non-aerated biological reactor, via denitrification, converts the nitrates in the second non-aerated biological reactor to nitrites;
• selectively supplying carbon sources contained in the second untreated water stream to the heterotrophic bacteria in the second non-aerated biological reactor to enable the heterotrophic bacteria to convert the nitrates in the second non-aerated biological reactor to nitrites;
• and
• wherein selectively supplying carbon sources to the heterotrophic bacteria in the second non-aerated biological reactor includes mixing a sufficient amount of the second untreated water stream with the treated first stream of water stream leaving the first aerated biological reactor such that the ratio of nitrite content to ammoniacal nitrogen content in the third water stream is approximately the stoichiometric ratio of the anammox reaction.

A method of biologically treating untreated water containing nitrogen and organic carbon, the method comprising:

• splitting the untreated water into a first untreated water stream and a second untreated water stream;
• directing the first untreated water stream into a first aerated biological reactor comprising filtering media and ammonium oxidizing bacteria, and subjecting the first untreated water stream to nitritation and filtration to produce a treated water stream;
• directing the treated water stream toward a second non-aerated biological reactor comprising media supporting anammox bacteria and heterotrophic bacteria;
• bypassing the first aerated biological reactor with the second untreated water stream;
• mixing the second untreated water stream with the treated water stream to form a combined stream, wherein the second untreated water stream supplies biodegradable organic carbon to the combined stream;
• adjusting a relative flow of the second untreated water stream with respect to the treated water stream such that a ratio of nitrite to ammoniacal nitrogen in the combined stream is approximately 1.3:1 on a molar basis;
• and
• introducing the combined stream into the second non-aerated biological reactor, wherein:
• (i) anammox bacteria perform deammonification based on said ratio, and
• (ii) heterotrophic bacteria utilize the biodegradable organic carbon supplied by the second untreated water stream to convert nitrates to nitrites.