Treating Wastewater

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Process

OVERVIEW

The City of Galt Wastewater Treatment Plant and Reclamation Facility (Plant) receives municipal and industrial wastewater from Galt and the immediate surrounding area. The Plant then provides preliminary, secondary and tertiary treatment to the wastewater before it is either discharged into Skunk Creek or applied to the adjacent City owned fields.

PRELIMINARY TREATMENT

Raw wastewater is pumped from the Live Oak Pump Station to the headworks of the WWTP. The headworks is where the primary treatment occurs. The inorganics such as trash and grit are removed using the screens and grit chamber.

Perforated Plate Screen

The influent first flows through a perforated plate screen at the headworks. The screen acts as a filter to remove rags, rocks, sticks, and other large debris to prevent them from damaging any equipment downstream.

Grit Removal  

Following the screen, the wastewater enters the grit chamber, where the wastewater is spun to allow the grit to settle while keeping the organic matter in suspension. The settled grit is washed and then trucked to a landfill.

SECONDARY TREATMENT

Secondary treatment consists of using biological floc to remove organic matter and nitrogen from the wastewater. This is done in two phases. The first phase takes place at the oxidation ditches, and the second at the secondary clarifiers.

Oxidation Ditches

The first phase of secondary treatment process is the oxidation ditches, where oxygen is supplied to the wastewater to remove nitrogen. Applying oxygen to the wastewater converts ammonia, a form of nitrogen, to nitrates.  The nitrates are then converted to nitrogen gas, which is then released into the atmosphere due to oxygen deprivation.                

OxDitched

Secondary Clarifiers     

From the oxidation ditches, a mixture of liquid and solids, called mixed liquor, flows to the Secondary Clarifiers, where the solids settle so that they can be pumped back to the ditches. The clear effluent overflows the clarifier weirs. The excess solids are wasted to the aerated lagoons for dewatering and disposal.  

SecondaryClarifiers (1)

TERTIARY TREATMENT AND DISINFECTION PROCESSES

Cloth Media Filters

The effluent from the secondary treatment process is distributed to three Disk Filters. This filtration system is composed of engineered, high performance cloth-media filters that are mounted in stainless steel filter tanks. As influent flows into the filter disks through the center tube of each filter, solids are trapped on the media and filtered effluent passes through into the filter vessel and out into the effluent piping.

Ultraviolet Disinfection     

Filtered effluent then flows through one of three channels of the ultraviolet (UV) disinfection system where it is exposed to UV light. The UV light irradiates pathogens rendering them unable to reproduce. Disinfected effluent then flows to the Effluent Diversion Structure for discharge.

EFFLUENT DISCHARGE AND RECYCLE

Final effluent is either discharged via a pipeline to a remnant channel of Skunk Creek or diverted to the existing storage reservoir, which is used to store partially or fully treated water for use on the City-owned agricultural fields.

Fields

BIOSOLIDS TREATMENT

Biosolids Storage Lagoons

Waste activated sludge and secondary scum are pumped to the two lined Biosolids Storage Lagoons. Each Lagoon has two floating mixers for mixing and aeration. Thickened bio solids are pumped from the mixed lagoon to the Dewatering Facilities. 

Sludge Drying Beds

The sludge is pumped from the biosolids storage lagoon to one of the Plant’s dewatering facilities, the sludge drying beds (drying beds), which is made of sand. When the solids are applied to the drying beds, the water from the sludge percolates through the sand and is caught by pipes at the bottom, then pumped back to the head works. The solids from the sludge remains at the surface of the drying beds until it is dry, which makes it less efficient during rain storms. The dried solids are then stored until they can be applied to the adjacent City owned fieldsSludge Drying Bed 2

Sludge Dewatering Screw Press Facility

Another one of the Plant’s dewatering facilities, which was an addition during the last Plant Upgrade Project, is the sludge dewatering screw press (screw press). The screw press is a mechanical instrument that dewaters the sludge regardless of the weather conditions. Such as the drying beds, the water removed from the sludge is pumped to the head works and the solids are stored until they can be applied to the City owned fieldsSludge De-Watering Press