Filtre x Filter#

Engineering, Analysis, Design & Construction Management Services

Surface water intakes - Impingement/Entrainment

Solutions to U.S. Environmental Protection Agency regulation for cooling water intake structures “Cooling Water Intake Structures—CWA §316(b)”




ized to force the desired flow through the filter. Under these conditions, a large quantity of water can be filtered through a relatively small size unit. In the proposed alternative installation orientation, the disc stacks are suspended  The solution utilizes an industrial filter directly in the stream flow from which the water is to be withdrawn and the withdrawal pump suction is connected to the central tube, thus drawing the water from the source, exterior to the disc stack and thence through the stack and into the pump section. Our field tests have indicated that with relatively small amounts of suction (10 to 15Ft) reasonable flow rates can be achieved  (Figure 1). At these flowrates the “capture manufactured by velocity” is <0.1fps and, therefore, when the filter element is immersed in the flowstream the filtered materials will typically not be retained on the filter media surface but will instead be carried along within the surrounding ambient flow. However, for items that are collected on the surface of the filter discs, the filter can be momentarily back-pulsed with reverse flow of an air/water mix, causing trapped material to be released to the prevailing ambient stream flow.  By installing multiple filter units in an array, say 6” on center, large flow rates can be achieved (Figure 2). 

  Determination of the size and orientation of the array is a function of the particular application.  For application to your system please contact us for an assessment of  the feasibility of the application to meet your needs.



There were few, if any, methods of dealing with this problem directly.  H&A investigated this problem in the context of surface water intakes in the application of water treatment systems.   As a result of these investigations into the issues of entrainment and impingement, it was determined that a modified installation arrangement of the Filtrex™ technology provided a solution that is both direct and unique.


The filter is comprised of disc stacks with radial penetrations leading to a central tube where the pressurized, filtered water is transmitted and discharged from the unit. The penetrations are typically sized from 5 to 50µ and the feed to the filter is normally pressur


EPA is developing regulations under §316(b) of the Clean Water Act. §316(b) requires that the location, design, construction and capacity of cooling water intake structures reflect the best technology available for minimizing adverse environmental impact. More than 1,500 industrial facilities use large volumes of cooling water from lakes, rivers, estuaries or oceans to cool their plants, including steam electric power plants, pulp and paper makers, chemical manufacturers, petroleum refiners, and manufacturers of primary metals like iron and steel and aluminum.

Cooling water intake structures cause adverse environmental impact by pulling large numbers of fish and shellfish or their eggs into a power plant's or factory's cooling system. There, the organisms may be killed or injured by heat, physical stress, or by chemicals used to clean the cooling system. Larger organisms may be killed or injured when they are trapped against screens at the front of an intake structure.

There are three rulemaking phases addressing cooling water intakes:

·           Phase I rule, promulgated in 2001, covers new facilities

·           Phase II rule, promulgated in 2004, covers large existing electric generating plants

·           Phase III rule, promulgated in 2006, covers certain existing facilities and new offshore and coastal oil and gas extraction facilities