Description
Chemical treatment involves adding chemicals to improve the treatment of target constituents. The key treatment processes are either sedimentation or disinfection, depending on the chemical added. Addition of coagulants stimulates floc formation, which increases the settling velocity of particles, and improves sedimentation. The primary constituents removed by the addition of coagulants are total suspended solids (TSS), total nitrogen and phosphorus, total and dissolved metals, microbiological constituents, and litter. The addition of other chemicals, such as hypochlorous acid (liquid form) or ozone (gaseous form), can disinfect stormwater by inactivating microbiological constituents.
Experience
Caltrans Tahoe Basin Small-Scale Pilot Studies – Chemical Treatment
The Caltrans Tahoe Basin Stormwater Pilot Program consists of both small-scale and full-scale pilot studies. Small-scale settling columns were constructed and operated intermittently to treat discrete batches of stormwater collected from various runoff events. The primary objective of this study was to determine the expected improvement in detention basin turbidity and nutrient removal from adding a flocculent or coagulant
OWP Tasks
- Assisted in Study Planning
- Reviewed Experimental Designs and Methods
- Provided Technical Assistance
- Assessed Study Results
- Reviewed Study Reports and Recommendations
Report/Study Link:
Caltrans Tahoe Basin Small-Scale Pilot Studies – Chemical Treatment
OWP Contacts: Dipen Patel | John Johnston
Caltrans Aquatic Toxicity Testing
Toxicity testing was conducted as part of a number of Caltrans studies in which effluent from treatment BMPs was discharged into receiving waters. EPA three-species bioassays (fathead minnow, water flea, and algae) were conducted, as well as a 96-hour bioassay for rainbow trout.
OWP Tasks
- Assisted in Study Planning
- Provided Technical Assistance During Toxicity Tests
- Assessed Study Results
- Reviewed Study Reports
Report/Study Link:
OWP Contacts: Dipen Patel | John Johnston
Caltrans Disinfection Reconnaissance Study
This study included conducting a literature review to identify information regarding the design and performance of disinfection systems for treating stormwater runoff. The information was used to develop preliminary designs and assess their feasibility for use in various Caltrans environments.
- Assisted in Literature Review
- Assisted with Review of Design Concepts
- Reviewed Feasibility Assessment and Report
OWP Contacts: Maureen Kerner
