A new low-pressure, high-intensity ultraviolet effluent treatment system can bring fecal coliform counts to less than 50 CFU per 100 mL, even in effluents that are cloudy, according to the manufacturer.
The Ultra Guard(tm) systems, offered by UV Systems Technology, Inc., have been tested and proven to be effective in disinfecting water with ultraviolet light transmission values below 20 percent.
The hydraulic nature of the reactor chamber causes the effluent to flow from the chamber wall toward the UV source, and then back to the chamber wall again. All of the effluent spends some of its time right at the UV source where it receives an intense dose of radiation, some of its time midway through the reactor where it receives a moderate dose, and some of its time near the reactor wall where it receives a low dose. The fluid oscillation also minimizes sedimentary deposit on the quartz sleeves.
Variations of flow and effluent transmission are handled by sensors capable of measuring flow and transmission, plus a diffuser inlet gate at the entrance to the channel. As the effluent enters and spreads into the channel, a diffuser screen intercepts the flow, mixes the layers and causes the fluid to flow towards the lamp module. This allows the system to set lamp intensity based on a consistent, predictable flow rate, which could be anywhere from 100 to 800 gpm.
A flow pacing device determines the volume of liquid flowing toward the disinfection modules; the ultraviolet transmission monitor provides continuous readings of the transmission quality. Then, a program in the system control center analyzes the readings to adjust the power settings for the UV lamps.
In multichannel installations, powered flow-control gates can be provided to balance the flow, control the number of modules in operation, or take a channel off-line for maintenance. The gates can be controlled remotely, and the remote system can take over other control and monitoring features provided by panel-mounted instruments.
The Flow-Balanced Weir makes sure the maximum surface of the lamp is immersed in fluid, controlling water level without movable gates or valves. Designed with the principle of atmospheric pressure equalization, the weir is installed at the same height as the UV lamps in the disinfection module.
Each lamp module system can handle 100 to 800 gpm, total suspended solids as high as 100 mg/L and UV transmission from 10 to 60 percent. Most test results on these specifications yielded log cycle reductions of between 2.5 and 4.8, according to the company. The systems are able to handle flows from hundreds of thousands to many hundreds of millions of gallons per day. They are custom-designed to suit site and discharge requirements.
The lamps are designed to respond to changing flow conditions with automatic sensing equipment. With a germicidal range of 250 to 280 nm, they are dimmed or brightened to optimize disinfection. The lamps can be replaced from above while the lamp module remains in the channel.
