Process for treating wastewater

Claim 1

A method of removing phosphorus and other pollutants from a pretreated wastewater stream having a relatively low BOD to phosphorus ratio comprising: a. separating suspended solids from the wastewater stream and conveying the suspended solids into a fermentation tank and the liquid fraction of the wastewater to further treatment; retaining the suspended solids in the fermentation tank a sufficient time to permit hydrolysis of the suspended solids so as to form soluble substrates; c. producing a side stream of return activated sludge; d. dividing the side stream of return activated sludge into at least two streams; e. mixing soluble substrates with the return activated sludge of one stream while generally separating the return activated sludge of the other stream from initial contact with the soluble substrates so as to effectively increase the food to mass ratio of the return activated sludge of the stream initially mixed with the soluble substrates; f. mixing the soluble substrates with return activated sludge and holding the mixture for a selected time period under anaerobic conditions to form conditioned return activated sludge; g. passing the liquid effluent from the primary treatment through a fixed film reactor and producing a pretreated wastewater effluent having a relatively low BOD to phosphorus ratio; h. mixing the low BOD to phosphorus effluent with the conditioned return activated sludge; and i. passing the mixture of pretreated effluent and return activated sludge through a series of treatment zones to effectuate the removal of phosphorus and other pollutants.

Claim 2

A method of removing phosphorus and other pollutants from a pretreated wastewater stream having a relatively low BOD to phosphorus ratio comprising: a. separating suspended solids from the wastewater stream and conveying the suspended solids into a fermentation tank and the liquid fraction of the wastewater to further treatment; retaining the suspended solids in the fermentation tank a sufficient time to permit hydrolysis of the suspended solids so as to form soluble substrates; c. producing a side stream of return activated sludge; d. dividing the side stream of return activated sludge into at least two streams; e. mixing soluble substrates with the return activated sludge of one stream while generally separating the return activated sludge of the other stream from initial contact with the soluble substrates so as to effectively increase the food to mass ratio of the return activated sludge of the stream initially mixed with the soluble substrates; f. mixing the soluble substrates with return activated sludge and holding the mixture for a selected time period under anaerobic conditions to form conditioned return activated sludge; g. passing the liquid effluent from the primary treatment through a fixed film reactor and producing a pretreated wastewater effluent having a relatively low BOD to phosphorus ratio; h. mixing the low BOD to phosphorus effluent with the conditioned return activated sludge; and i. passing the mixture of pretreated effluent and return activated sludge through a series of treatment zones to effectuate the removal of phosphorus and other pollutants.

Claim 13

A method of treating wastewater comprising: a. subjecting wastewater to primary treatment and producing a primary effluent; b. directing the primary effluent to a secondary treatment area and through a series of secondary treatment zones so as to produce a purified effluent and a return activated sludge stream; c. returning the return activated sludge in a side stream; d. splitting the return activated sludge into at least two streams; e. transferring the return activated sludge of at least one stream to a feeding cell while the return activated sludge of the other stream is at least initially separated from the return activated sludge of the first stream; f. initially directing soluble substrates into the feeding cell where the soluble substrates are brought first into contact with the return activated sludge in the feeding cell where the food to mass ratio has been effectively increased because of the isolation of the other stream of return activated sludge, thereby producing a more favorable environment for the selection, growth and proliferation of certain microorganisms; g. mixing soluble substrates with the return activated sludge in the feeding cell and holding the mixture in the feeding cell for a selected time period to form conditioned return activated sludge; and h. conveying the return activated sludge, including the return activated sludge from both streams, back to the secondary treatment area where the return activated sludge is mixed with wastewater passing through the secondary treatment zones.

Claim 14

A method of treating wastewater comprising: a. subjecting wastewater to primary treatment and producing a primary effluent; b. directing the primary effluent to a secondary treatment area and through a series of secondary treatment zones so as to produce a purified effluent and a return activated sludge stream; c. returning the return activated sludge in a side stream; d. splitting the return activated sludge into at least two streams; e. transferring the return activated sludge of at least one stream to a feeding cell while the return activated sludge of the other stream is at least initially separated from the return activated sludge of the first stream; f. initially directing soluble substrates into the feeding cell where the soluble substrates are brought first into contact with the return activated sludge in the feeding cell where the food to mass ratio has been effectively increased because of the isolation of the other stream of return activated sludge, thereby producing a more favorable environment for the selection, growth and proliferation of certain microorganisms; g. mixing soluble substrates with the return activated sludge in the feeding cell and holding the mixture in the feeding cell for a selected time period to form conditioned return activated sludge; and h. conveying the return activated sludge, including the return activated sludge from both streams, back to the secondary treatment area where the return activated sludge is mixed with wastewater passing through the secondary treatment zones.

Claim 24

A method of treating wastewater comprising: a. subjecting wastewater to primary treatment and producing a primary effluent; b. directing the primary effluent to a secondary treatment area and through a series of secondary treatment zones so as to produce a purified effluent and a return activated sludge stream; c. returning the return activated sludge in a side stream; d. splitting the return activated sludge into at least first and second streams; e. transferring return activated sludge of the first stream to a feeding cell and directing the second stream of return activated sludge to a separation cell; f. initially directing soluble substrates into the feeding cell where the soluble substrates are brought first into contact with the return activated sludge in the feeding cell where the food to mass ratio has been effectively increased because of the separation of the first and second streams of the return activated sludge, thereby producing a more favorable environment for the selection, growth and proliferation of certain microorganisms; g. mixing soluble substrates with the return activated sludge in the feeding cell and holding the mixture in the feeding cell for a selected time period to form nutrified return activated sludge; h. transferring the nutrified return activated sludge from the feeding cell to the separation cell and mixing the nutrified return activated sludge of the feeding cell with the return activated sludge of the separation cell to form a conditioned, nutrified return activated sludge mixture; and i. conveying the conditioned, nutrified return activated sludge mixture back to the secondary treatment area where the same is mixed with waste water passing through the secondary treatment zones.

Claim 25

A method of treating wastewater comprising: a. subjecting wastewater to primary treatment and producing a primary effluent; b. directing the primary effluent to a secondary treatment area and through a series of secondary treatment zones so as to produce a purified effluent and a return activated sludge stream; c. returning the return activated sludge in a side stream; d. splitting the return activated sludge into at least first and second streams; e. transferring return activated sludge of the first stream to a feeding cell and directing the second stream of return activated sludge to a separation cell; f. initially directing soluble substrates into the feeding cell where the soluble substrates are brought first into contact with the return activated sludge in the feeding cell where the food to mass ratio has been effectively increased because of the separation of the first and second streams of the return activated sludge, thereby producing a more favorable environment for the selection, growth and proliferation of certain microorganisms; g. mixing soluble substrates with the return activated sludge in the feeding cell and holding the mixture in the feeding cell for a selected time period to form nutrified return activated sludge; h. transferring the nutrified return activated sludge from the feeding cell to the separation cell and mixing the nutrified return activated sludge of the feeding cell with the return activated sludge of the separation cell to form a conditioned, nutrified return activated sludge mixture; and i. conveying the conditioned, nutrified return activated sludge mixture back to the secondary treatment area where the same is mixed with waste water passing through the secondary treatment zones.