Wastewater treatment system including multiple stages of alternate aerobic-anerobic bioreactors in series

In a method for the treatment of industrial or municipal wastewater of a type including organic carbon and nitrogen-containing nutrients, the steps of

• (a) forming a plurality of aerobic zones, each zone including multiple channels defined by spaced-apart exposed support surfaces upon which aerobic microorganisms grow in fixed films,
• (b) forming a plurality of anaerobic zones, each zone including multiple channels defined by spaced-apart exposed support surfaces upon which anaerobic microorganisms grow in fixed films, said aerobic zones and anaerobic zones being arranged in a series of alternate aerobic and anaerobic zone pairs including at least a first aerobic-anaerobic zone pair and a last aerobic-anaerobic zone pair,
• (c) passing said wastewater into the upper portion of said first aerobic zone and causing it to flow downwardly through said channels under the influence of gravity in at least partially film form exposed to air along said aerobic microorganisms fixed films on their support surfaces for intimate contact between said aerobic microorganisms and said wastewater in the presence of oxygen to thereby cause incremental consumption of the organic carbon nutrients and incremental conversion of organic nitrogen nutrients to ammonia and nitrification of the thus-formed ammonia to nitrate,
• (d) passing the treated wastewater as a stream from said first aerobic zone to said first anaerobic zone in which said anaerobic microorganism film is submerged in an anaerobic environment and causing said wastewater stream to flow through said channels past said anaerobic microorganism fixed films for intimate contact to cause further incremental consumption of said organic carbon nutrients and incremental denitrification of nitrate to nitrogen gas,
• (e) passing the effluent from the first anaerobic zone to the upper portion of the last aerobic zone and causing it to flow downwardly through said channels under the influence of gravity in at least partially film form exposed to air along said aerobic microorganisms fixed film on their support surfaces for intimate contact between said aerobic microorganisms and said wastewater in the presence of oxygen to thereby cause further incremental consumption of the organic carbon nutrients and incremental conversion of organic nitrogen nutrients to ammonia and nitrification of the thus-formed ammonia to nitrate,
• (f) passing the effluent from the last aerobic zone to the last anaerobic zone in which said anaerobic microorganism film is submerged in an anaerobic environment and causing said wastewater stream to flow through said channels past said anaerobic microorganism fixed films for intimate contact to cause further incremental carbon consumption of the organic carbon nutrients and incremental denitrification of nitrate to nitrogen gas, sufficient organic carbon being present in the effluent directed to the last anaerobic zone to cause significant denitrification to occur therein.