Wastewater Treatment

Dangers of Not Treating Wastewater-Waterborne Disease Cholera Typhoid Fever Hepatitis Amoebic Dysentery Giardiasis E.Coli 0157:H7 Cryptosporidiosis

Goal of Wastewater Treatment Protect the downstream user and the environment To accomplish the goal –Remove contaminants –Remove/inactivate disease-causing organisms

Types of Contaminants Large items –Sticks –Rags Inorganic materials –Sand –Clay –Eggshells Organic chemicals –Pesticides –Herbicides Microorganisms

Treatment Plant Processes Screening Grit removal Biological treatment Clarification Filtration Disinfection Dechlorination Solids Handling –Digestion –Thickening –Dewatering

Screening Removes large items from the wastestream –Rags –Sticks –Power Rangers –Barbie Dolls

Grit Removal Removes inorganic contaminants from the wastestream –Slow flow to 1 ft/sec –Inorganic solids settle out –Removed by a conveyor with buckets

Biological Treatment Microorganisms biodegrade the organic matter Break it down into non-harmful components

Clarification Slows the flow of water down Sludge settles to the bottom and is returned to the basin or sent to the digester Clear water is sent to filtration or disinfection

Filtration Reed Creek has a sand filter Little River has a disk filter with a cloth media Purpose is to remove colloidal and fine particulate matter

Disinfection Purpose is to kill or inactivate pathogenic microorganisms Chlorination –Reed Creek –Crawford Creek –Kiokee Creek UV Disinfection –Little River

Dechlorination Chlorine can be harmful to aquatic life Sulfur dioxide is added to remove the residual chlorine just prior to the water being discharged into the receiving stream.

Solids Handling Sludge that settled to the bottom of the clarifier is returned to the basin or sent to the digester Excess solids are pumped to an aerobic digester Air is added –To provide oxygen for microorganisms –To prevent odors

Thickening When digester is full, air is turned off Solids settle out Clear water from the top is returned to the plant More space is created in digester Eventually no solids settle out

Mechanical Dewatering Utilizing mechanical force to remove water from the solids Centrifuge at Reed Creek Belt Press at Little River

Natural Dewatering Drying Beds- at RC, CC, and LR –Gravity feed sludge into bed –Water removed through evaporation and percolation –Dried sludge is collected and taken off-site

Performance Monitoring Required by a state NPDES permit to collect and analyze certain samples –Operators analyze some –Laboratory analyzes some Collect and analyze samples daily Incoming water quality –Helps determine plant efficiency Filtration rates to determine when to backwash filters Percent solids of material taken to landfill

Performance Monitoring Outgoing water quality –Chlorine residual –pH –Fecal coliform bacteria –Total suspended solids –Ammonia –Biochemical oxygen demand –Copper

Review Wastewater Treatment Purpose is to protect the downstream user and the environment Accomplish the goal through treatment processes –Screening –Grit removal –Biological treatment –Clarification –Filtration –Disinfection –Dechlorination –Solids Handling