Treatment of wastewater

Abstract

Process and apparatus for the oxidation of carbonaceous and nitrogeneous matter in wastewater by use of a mixture of biologically active slimes attached to partially submerged rotating contactors. The biological contactors are mounted in a single-stage treatment unit and are supplied with wastewater at a controlled rate relative to the surface of the contactors and distributed substantially evenly over the contactor surface. A denitrifying unit, located upstream from the single-stage treatment unit is supplied with wastewater and recirculated effluent from the single-stage treatment unit. The denitrifying unit utilizes biologically active slimes attached to rotating biological contactors for the removal of carbonaceous matter from the wastewater supported by nitrate oxygen from the recirculated effluent.

I claim: .Iaddend. 
     
       1. A method for treating wastewater containing carbonaceous pollutants measured as BOD 5  and ammonia nitrogen in a weight ratio of at least 3.6:1 respectively, comprising the steps of supplying said wastewater at a predetermined rate to a .Iadd.single stage .Iaddend.biological treatment unit that includes .[.not more than a single.]. .Iadd.at least one .Iaddend.rotatable shaft supporting a plurality of partially submerged biological contactors having surface area for the growth and maintenance of organisms, creating a flow of said wastewater through said biological treatment unit in a direction generally perpendicular to said rotatable shaft .Iadd.so as to feed the organisms on said contactor surfaces substantially equally, .Iaddend.and rotating said shaft to impart a predetermined peripheral velocity to said biological contactors to alternately expose said surface area to wastewater and an oxygen containing atmosphere, said predetermined rate and peripheral velocity being chosen to simultaneously oxidize at least about 83 weight percent of said carbonaceous pollutants measured as BOD 5  and at least about 46 weight percent of said ammonia nitrogen on the same surface area of said contactors. 
     
     
       2. The method of claim 1 wherein said oxygen containing atmosphere comprises from 30 to 60 percent oxygen by volume and said predetermined rate is from 1 to .Badd..[. 25.]..Baddend. .Iadd.2.5 .Iaddend.gallons per day per square foot of said surface area. 
     
     
       3. The method of claim 1 wherein said predetermined rate is from 0.4 to 1.5 gallons per day per square foot of said surface area and said peripheral velocity is from 0.25 to 1.0 ft/sec. 
     
     
       4. The method according to claim 1 wherein said predetermined rate is from about 0.4 to about 2.5 gallons per day per square foot of said surface area. 
     
     
       5. The method according to claim 4 wherein the wastewater temperature is greater than about 60° F. 
     
     
       6. A method for treating wastewater containing carbonaceous pollutants measured as BOD 5  and ammonia nitrogen in a weight ratio of at least about 3.6:1 respectively, comprising the steps of supplying said wastewater at a predetermined rate to a .Iadd.single stage .Iaddend.biological treatment unit that includes .[.not more than a single.]. .Iadd.at least one .Iaddend.rotatable shaft supporting a plurality of partially submerged biological contactors having surface area for the growth and maintenance of organisms, creating a flow of said wastewater through said biological treatment unit in a direction generally perpendicular to said rotatable shaft .Iadd.so as to feed the organisms on said contactor surfaces substantially equally, .Iaddend.and rotating said shaft to impart a predetermined peripheral velocity to said biological contactors to alternately expose said surface area to wastewater and an oxygen containing atmosphere, said predetermined rate being from 0.4 to 1.5 gallons per day per square foot of said surface area, whereby the same surface area of said contactors is used to simultaneously oxidize at least about 83 weight percent of said carbonaceous pollutants measured as BOD 5  and at least about 46 weight percent of said ammonia nitrogen. 
     
     
       7. The method according to claim 6 wherein said peripheral velocity is from 0.25 to 1.0 ft/sec. 
     
     
       8. The method according to claim 6 wherein said wastewater contains at least about 109 milligrams per liter of BOD 5  and at least about 25 milligrams per liter of ammonia nitrogen.