Mounting concerns over safety, effluent toxicity, air emissions, and rising chemical costs are compelling many publicly owned treatment works (POTWs) to reevaluate the use of gaseous chlorine for wastewater disinfection. Typical alternatives to gaseous chlorine for disinfection include sodium hypochlorite/sodium bisulfite — which requires installing new chemical storage, containment, and handling systems — and ultraviolet radiation (UV). Knowing which alternative is best for your facility takes hands-on experience. Successful project implementation also requires the ability to match the right technology and equipment vendor with your needs. At Carollo Engineers, we are suited to the challenge.
Disinfection with ultraviolet radiation can offer several advantages under the right circumstances. UV alters the genetic material in bacteria, viruses, and other microorganisms, rendering them unable to reproduce. Because it uses no chemicals, it is safer for operators, the public, and the environment. UV disinfection also works faster and may offer lower capital and operating costs than other disinfection methods. Deciding if UV is the optimal disinfection method for a POTW frequently involves:

• Setting policies regarding the safety and relative risk of gaseous chlorine facilities.
• Determining the effects of water quality parameters such as total suspended solids, turbidity, and transmittance on required UV dosage.
• Establishing the UV dosage necessary to meet effluent requirements.
• Integrating the UV disinfection system with plant operations, including hydraulics, electrical power systems, and instrumentation.
• Comparing available types of UV equipment, including low and medium pressure UV systems.
Carollo offers a full range of services for UV disinfection system implementation.

• Pilot and bench-top testing programs
• Transmittance testing
• Preliminary design
• Equipment pre-purchase
• System integration
• Permit negotiations and agency coordination
• Full-scale design and construction services
• Program management
Our engineers have evaluated alternative disinfection methods and performed pilot/bench-top testing and design of UV disinfection systems for clients throughout the U.S.