Denitrification system

DETAILED DESCRIPTION The objects are accomplished in accordance with the invention by the provision of a multistage system for the effective reduction of nitrogen compounds and suspended solids comprising a fixed film biological reactor and an automatic backwash filter that fits into a typical wastewater treatment plant as shown in the schematic diagram of FIG.
8.
Methanol, or another type of carbon donor, is fed ahead of the biological reactor to provide the carbon necessary for the denitrifying bacteria in the reactor.
Methanol is normally the preferred source for the carbon and approximately 3 pounds of methanol is typically fed per pound of nitrate-nitrogen.
The denitrifying reaction takes place under anoxic conditions, basically no free oxygen.
The dissolved oxygen content should not be more than a few tenths mg/l for the most rapid and complete denitrification.
The denitrification is a two or three step reaction where the nitrates and nitrites are eventually reduced to nitrogen gas.
A simplified denitrification reaction is as follows: NO.
sub.
3 +0.
833CH.
sub.
3 OH.
fwdarw.
0.
833CO.
sub.
2 +0.
5N.
sub.
2 +1.
167H.
sub.
2 O+OH The bacteria in the reactor require oxygen to thrive and, in the absence of free oxygen, the bacteria utilize the molecular oxygen available from the nitrate (NO.
sub.
3) and nitrite (NO.
sub.
2) compounds in the wastewater.
The influent water to be treated flows into a bottom distribution system through a series of pipes branching across the biological reactor.
The flow is then up through a media system which supports the denitrifying bacterial growths.
The media configuration provides continuous and uniform horizontal redistribution of the flow.
As the flow passes through the bacteria, the denitrifying reactions occur.
The upward movement of the flow also carries the nitrogen gas bubbles up to the surface of the media and out to the atmosphere.
The flow cascades over weirs or collector pipes with orifices into a series of collector troughs.
The flow is from the collector troughs through a pipe from each trough to an aerated chamber