Algae growth on launder trough and weir surfaces is a continuous operations and maintenance problem in treatment plants everywhere. At its most benign level, algae is an unsightly nuisance that requires frequent cleaning by plant personnel. This is a costly, continuous process that robs valuable time of maintenance personnel. Unchecked, algae growth can have more severe and expensive consequences, disrupting weir overflow and clogging filter screens and pump mechanisms. In plants equipped with UV disinfection systems, algae in the effluent may significantly reduce the systems' effectiveness and cause serious maintenance issues.
NEFCO's patented* Launder Cover Systems have been designed specifically to inhibit the growth of algae on the launder trough and weir surfaces by blocking sunlight from striking those areas. Without sunlight, the algae is largely eliminated or reduced to a light film that is easily washed away with a hose. Constant cleaning by maintenance personnel is a thing of the past, as is the threat of operations or equipment problems caused by algae growth.
Launder Covers generally consist of a fixed Mounting Section, which serves as the base for the Cover, and a hinged Cover Section that opens to provide access for inspection and maintenance. Together, these two sections extend from the tank wall over the trough and weir and to a point just on the inboard side of the scum baffle.
There are two basic cover configurations. The first is the Tank Wall Configuration where the Mounting Section attaches to the outer tank wall and the Cover opens back toward the outer wall. The second is the Weir Wall Configuration where the Mounting Section is fastened to the weir wall and the Cover opens inward toward the center of the tank and away from the operator.
The Weir Wall Configuration overcomes these problems:
NEFCO offers both Cover configurations, but the Weir Wall Mounted Cover is the choice of most plant personnel. The Weir Mount section is secured over the weir wall with stainless steel brackets. The hinged Cover Section arches over the trough and rests on a cover support flange fastened to the tank wall. Alternate panel units feature a molded tab that seals the panel seams from sunlight. NEFCO has taken this design one step further and offers the Weir Wall configuration with integral scum baffle.
There is also a NEFCO Launder Cover System designed for radial troughs or situations where the trough is set away from the outer tank wall. In these cases the Cover is configured as a hinged hood supported on both sides of the launder trough. NEFCO has also developed and patented a cover system designed specifically for peripheral feed clarifiers with a variable width effluent channel.
Each Cover panel is manufactured of tough uv-protected fiberglass and specifically designed to withstand the rigors of both the application and the environment. The Cover System is custom engineered to the specific configuration and dimensions of the clarifier for optimum performance and ease of installation. Once installed, and unlike 'brush' or 'sweep' systems, the Cover operates 24/7/365, requires virtually no maintenance and has no parts to be replaced.
NEFCO has been granted several US patents for its Launder Cover System designs, including Patents 5,670,045; 5,965,023; 6,216,881; 6,712,222; 7,473,358 and 7,591,381.
It is estimated that more than 80% of the odors in the clarifier are produced when the effluent breaks over the weir. NEFCO Odor Covers are designed to contain these odors to prevent them from creating a nuisance and/or operate in conjunction with scrubber systems that draw the trapped gases off and treat them to eliminate the odor. NEFCO Covers are an essential element in an effective odor control system.
In addition, the Cover acts to keep ice, snow and debris from the launders, adding to the overall appearance and operation of the facility.
Although NEFCO engineers have adapted our Algae Cover systems for use in odor control applications, NEFCO also makes a full line of rugged, walk-on Odor Cover Systems. These covers feature heavily reinforced laminates with molded non-skid surfaces. NEFCO offers large platform covers with inset inspection hatches, as well as covers made as a series of individual hinged cover sections, each of which opens completely. All of these covers are designed to contain gases and operate in conjunction with external odor control equipment.
NEFCO Odor Covers provide a safe working environment for plant personnel. The covers are designed to meet the specified load requirements with generous safety factors, and provision is made to accommodate safety railings where necessary.
In addition to odor covers for clarifier launder troughs, NEFCO provides similar cover systems for other facilities throughout the plant. In these cases, a grid system of FRP, galvanized steel or stainless steel beams is supplied to form a support structure over the opening, and a series of cover panels are fastened in place. Some or all of the cover panels can be hinged to open.