Gillian Chew

Collections Gates are commonly used within a collection system to control flows. Automation of these gates requires an actuator that can reliably respond to changing conditions. During a wet weather event, the actuators on these gates are the critical aspect of the entire high flow management strategy. A failure of actuators to respond can cause big problems. Imagine a scenario where a collection system interceptor station has both influent control and diversion gates. The flow typically runs through the control gate that can be modulated to pinch off or shut off flows, perhaps using in-house storage upstream within the collection system. During very high flow events, the diversion gate would divert to a local water way or a storage area.  The worst case scenario occurs if the control gate is pinched off/closed, but the diversion gate fails to open on account of an actuator failure. During an extreme wet weather event, such a failure could cause flooding upstream of this interceptor, potentially resulting in public or private infrastructure damage, as well as a black eye for the wastewater operations.  Literature Download the Collections Wet Weather Management Application Spotlight! Download

UV Disinfection Background Wastewater treatment plants often employee ultraviolet (UV) disinfection as the last stage of treatment to meet strict bacterial limitations on plant discharges. A UV system’s reliability and efficiency is critical to mitigating the threat of permit violations and fines for the discharge of improperly disinfected wastewater effluent. During the UV disinfection process, treated wastewater is exposed to UV light, causing cellular damage to any microorganisms present. Therefore, these pathogens, such as viruses and bacteria, are incapable of reproduction or infection.  On open channel UV systems, either a controlling gate or weir structure regulate and maintain constant water levels over the UV lamps. For UV systems with horizontally-installed lamps, it is imperative to properly regulate wastewater levels to provide sufficient  UV exposure to contaminants. In addition, the UV system effluent gates serve as one of the last points of control before discharge.  Problem Poorly-controlled actuators on this application leads to a variety of problems. If the gate cannot accurately control the water level over the UV lamps and gets too high, there may not be enough UV light to treat the additional water flowing through the channel. Consequently, this leads to potential discharge permit violations. Conversely, if the water level gets too low, the UV lamps can overheat, leading to maintenance issues. From a fail-safe perspective, if the UV system is compromised for any reason, and the effluent gate does not close, the plant can discharge non-permit water.  Solution The reliability of REXA Linear and Rotary Actuators prevents downtime and maintenance costs on UV applications. More importantly, the superior control capabilities of REXA Linear and Rotary Actuators assures proper level control in plants’ UV channels. This allows them to meet disinfection standards for their effluent, reduce the threat of fines, and maximize UV bulb life. The easy addition of a fail-safe option to any REXA design gives the treatment plant peace of mind that a UV channel can be closed and isolated when an upset or emergency condition occurs. UV effluent control structures are tailor-made for the reliability, control, and fail-safe capabilities offered by REXA. Literature Download the UV Disinfection Effluent Level Control Application Spotlight! Download

Headworks It is common for one or more cast iron sluice gates to be employed within the headworks of a wastewater treatment plant to control the flows entering the facility from the collection system. These gates will most often remain fully open, but can be throttled to regulate flows during high-flow events. Above all, reliability of these sluice gates is of great importance to the treatment plant.  Many facilities do not modulate the main influent gates in the headworks due to the inoperability of the existing actuators. In such instances, the gates may be permanently chained in the open position, preventing the plant from fully utilizing the control structures in the headworks. Regardless, if the actuator controlling a headworks gate becomes inoperable to the point that it impedes or disrupts the flows coming into the wastewater treatment plant, big problems can arise by allowing too much or too little flow into the treatment plant.  REXA  Linear  and  Rotary  Actuator’s are ideal for headworks gates, allowing a plant to reliably operate these gates, as well as control and modulate them (an added benefit many plants do not yet employ). 

Clarifiers REXA Linear  and  Rotary  Actuators have been employed on modulating valves/gates that are used to maintain accurate level control for clarifiers, with some installations controlling water levels with accuracies of less than 0.5″ set-points.

Sludge Control Moving and modulating sludge flow can be a difficult service given the viscous nature of sludge. REXA  Electraulic™  Technology  is ideally suited to help gain control of any flow control sludge applications in a treatment plant. REXA has many installations on modulating sludge control valves where actuators have performed flawlessly for 10+ years and counting.