Biomass selection and control for continuous flow granular/flocculent activated sludge processes

In a biological wastewater treatment system, a classifier for separating granular sludge from flocculent sludge, comprising:

• a tank or vessel, having an infeed of biomass sludge to the tank including both granular and flocculent sludge,
• an energy dissipating inlet in the tank and receiving the infeed and dispersing it into the tank at a reduced velocity,
• the tank having an effluent outflow near the top of the tank, causing a flow pattern in the tank ultimately upwardly toward the outflow, such that the upward flow carries primarily floc biomass of less density than granular biomass to the outflow, while primarily granular biomass, with higher density than the floc biomass, settles toward the bottom of the tank to accumulate at the bottom of the tank, and
• at the bottom of the tank, a bottom outflow for removal or recycle of granular floc,
• whereby a majority of biomass at the bottom outflow of the tank is granular biomass, and a majority of biomass effluent exiting the outflow near top of the tank is floc biomass.

A method for enhancing biological nitrogen and/or phosphorus removal from sanitary sewage wastewater, in a continuous flow process, comprising:

• operating a biological MLSS process in one or a succession of process zones, to remove nitrogen or nitrogen and phosphorus from activated sludge, and continuously receiving new raw influent wastewater into the process zones, a first zone of said process zones being an anaerobic or anoxic zone,
• directing sludge flow from the biological MLSS process zone(s) through a classifier through which sludge flows and in which granular sludge is mostly separated from floc sludge,
• directing primarily granular sludge in a granular recycle flow from the classifier back to one of the biological process zones,
• directing primarily floc sludge out of the classifier and to a clarifier where sludge settles to the bottom of the clarifier,
• recycling a major portion of the settled sludge from the clarifier to one of the process zones,
• in a classifier recycle, increasing flow into the classifier either by returning a portion of the primarily floc sludge exiting the classifier to an input of the classifier or by increasing the recycle of settled sludge from the clarifier, when the classifier recycle is operated,
• with a classifier bypass line, bypassing a portion of sludge from the biological process around the classifier when the classifier bypass line is operated,
• operating the classifier recycle and the classifier bypass line to maintain a flow rate into the classifier within a desired range during influent flow variations, by increasing flow through the classifier recycle when influent flow falls below the desired range and increasing flow through the classifier bypass line when influent flow exceeds the desired range,
• operating the classifier such that granular sludge separated out in the classifier is in a size range from about 0.3 to 3.0 mm, and
• operating the classifier and wasting settled sludge from the classifier and from the clarifier at such rates as to establish a desired ratio of granular sludge to floc sludge in the process zones.

A classifier within a clarifier in a system for biological treatment of wastewater including organic sewage, comprising:

• a clarifier tank with an inflow pipe receiving activated sludge from upstream liquid process zones of the system,
• the classifier including an energy dissipating inlet connected to the inflow pipe and receiving sludge having both floc and granular biomass,
• the energy dissipating inlet having a top plate and a bottom plate and internal baffles configured to direct sludge in generally open distribution radially outwardly into liquid volume of the clarifier, such that sludge solids settle by gravity to a tank floor sloped downwardly toward the center of the clarifier, with granular sludge settling faster than floc sludge and the floc sludge settling slower and more outwardly,
• the classifier further including the clarifier having a granular sludge exit through the tank floor, near the center of the classifier, and a floc sludge exit through the tank floor spaced outwardly from the granular sludge exit,
• the classifier further including an annular sludge dividing deflector plate extending up from the tank floor and positioned radially inwardly from the floc sludge exit, so that floc sludge, which tends to settle more slowly and travel farther outwardly in the clarifier than granular sludge, tends to settle on the tank floor outwardly of the dividing deflector plate while the denser granular sludge tends to settle inwardly of the dividing deflector plate,
• whereby sludge exiting the granular sludge exit has a higher concentration of granular sludge than sludge exiting at the floc sludge exit of the clarifier.

In a wastewater treatment system, a sidestream treatment process for generating granular biomass for use in a mainstream process for removing nitrogen and/or phosphorus, comprising:

• operating a biological sludge process in one or a succession of process zones, to remove nitrogen or nitrogen and phosphorus from activated sludge, and continuously receiving solids processing reject water or influent wastewater into the process zones, a first zone of said process zones being an anaerobic or anoxic zone,
• directing sludge flow from the biological sludge process zone(s) through a classifier through which sludge flows and in which granular sludge is mostly separated from floc sludge, and collecting primarily granular sludge in a bottom area of the classifier,
• recycling a majority of the primarily granular sludge to the first zone so as to feed the granular biomass with influent soluble bCOD, and
• wasting a sidestream comprising some of the primarily granular sludge to the mainstream process.