CST Wastewater Solutions curtails blockages, spills and maintenance issues

Roseville, Australia - Advanced wastewater fine screening technology from CST Wastewater Solutions is engineered to curtail blockages, spills, maintenance and associated occupational health and safety issues in pulp and paper industry wastewater treatment plant applications.

The robustly engineered horizontal in-channel rotary drum screening technology is designed to simplify fine screening processes and save installation and operational costs while curtailing downtime hazards, said Michael Bambridge CST Wastewater Solutions managing director.

The low-maintenance highquality, stainless steel design features in-channel technology for low fluid head loss at peak flows to increase solids removal efficiency when compared with typical traditional screening.

“Advantages of this technology when dealing with fine screening of larger flows (5mm or finer screening on flows up to 2000 l/sec flow) include mechanical simplicity, self-cleaning and high efficiency screening for reduced maintenance and cheaper whole-oflife costs compared with other types of screens, such as band and inclined drum screen designs, for example,” said Bambridge.

Key to this functionality is the configuration of the design, in which the screening drum is installed horizontally semi-submerged in line with the incoming wastewater. The plate at the back of the drum directs flow through the mesh to optimize solids separation and self-cleaning.

The rotary drum is manufactured from either selfcleaning wedge wire for primary screening, or perforated plate for fine pre-membrane bioreactor (pre-MBR) screening. It is washed by a system of spray nozzles at a moderate pressure.

An internal hopper collects the screenings, which are flumed out to the integral lifting and dewatering screw, to efficiently dewater and reduce screenings volume. The lifting screw is shaftless to avoid any blockages, even in the presence of fibrous products, and includes screen and screening washing. Lifting and screenings handling can also be conducted outside the channel, which increases options for additional washing and dewatering, according to individual applications, said Bambridge.

“Screening and the solids lifting and dewatering are separate operations, using high efficiency screening technology to convert the high-flow, low-solids wastewater to low-flow, high-solids dewatering. Separate screening and lifting equipment makes access simpler for more cost-effective housekeeping and maintenance for lower wholeof- life costs,” he said.

The advantages of the horizontal drum design are numerous. It lowers operating depth and range to reduce average screen velocities for higher removal efficiencies, and easier cleaning than alternative screens. The robust construction is tailored to local conditions. The onepiece, closed drum is fully assembled in a frame for installation into a channel. It incorporates a simple, longlife, robust inlet seal that can be replaced without removing all equipment from the channel. All the parts subject to routine maintenance are located above the sewage flow and simply maintenance and occupational health and safety issues.

Screening and lifting screw equipment are proven, simple and robust technologies. No bearings or other high maintenance moving parts are located in the wastewater. Housekeeping and servicing are conducted from above the flow channel. No mechanical devices are used inside the screen drum. There is an open entry for clean collection of solids. The screen zone of the lifting screw incorporates a washing system to reduce the contents of faecal matter in the screenings.

CST Wastewater Solutions www.cstwastewater.com

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