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ENGINEERING DESIGN MANUAL -- TREATMENT AND DISPERSAL PACKAGES: RESIDENTIAL & COMMERCIAL

SECTION IX

CHLORINE DISINFECTION

Chlorination is the most common method of disinfection for wastewater discharges. Contact time and mixing must be provided for chlorine to kill the bacteria in the wastewater stream. The contact time will differ based on the potential for the contact reactor to short circuit. Many codes will allow a design of 30 minutes retention only if a contact chamber is provided with a 20:1 length to width ratio for proper contact time.

REACTOR DESIGN

The American Manufacturing Company Chlorine contact chamber provides both a 20:1 ratio and 30 minute contact time for residential gravity flows. The Chlorine Contact Chamber is designed with an up and down flow pattern using three modules in series to achieve an average 20:1 length to width ratio. The water will flow down the 4" diameter drop pipe and then rise in the 13" wide (average) box. The resulting turbulence will enhance mixing. In conventional chambers the length to width ratio is based on rectangular shapes. The drop pipe is circular plus being in the center of the box it will decrease the flow path between the pipe and the sidewall resulting in a better than conventional configuration.

SPECIFICATION

Chlorine Contact time shall be provided to kill bacteria in the wastewater effluent. The chlorine contact chamber shall provide a 20:1 average length to width ratio and sufficient contact time for the effluent flow. American Manufacturing Company , Inc. will provide a Chlorine Contact Chamber with a minimum of 3-modules (75 gallons) and add more modules for added capacity as required.

PUMP SYSTEMS

Pump systems represent a difficult problem for chlorine contact due to the potential peak flow rates. In order to assure proper contact time, 1) the contact chamber should be sized for the design discharge rate of the pump or 2) the pump should be controlled by a timer to provide a dose in an amount smaller than the chamber with enough time to provide for sufficient contact time or 3) the liquid level drawdown should not exceed the chamber capacity and a lockout timer should be provided to assure the proper contact time during peak flows.

CHLORINATOR
CHLORINE CONTACT MODULE
Tablet Chlorinator

TABLET CHLORINATOR

The LF-2000 Tablet Chlorinator is a complete chlorine dispensing system. The Model LF-2000 has a 4 1/2" diameter inlet and outlet. It is designed to handle the flow of treated effluent for design flows up to 1500 gallons per day. The Norweco Tablet Chlorinator has no moving or electrical parts. It uses Disinfecting Tablets - not powders or gases. The Chlorinator works by gravity flow alone - chlorine dosage automatically adjust with increases and decreases in effluent flow.

HOW THE CHLORINATOR WORKS

The Tablet Chlorinator consists of a housing and two tablet feed tubes. The chlorinator is installed directly in the ground on the discharge line so the discharge flows through it. Feed tubes and a chlorine contact channel control the direction of flow within the chlorinator. Slow dissolving tablets at the bottom of the feed tubes are immersed in the effluent. They dissolve evenly, slowly releasing active chlorine. The rate at which the tablets dissolve is regulated automatically by the liquid height and by varying the amount of tablets in contact with the effluent. When the flow of effluent increases, the liquid level in the housing rises, covering more tablets and releasing more chlorine. When the flow decreases, the liquid goes down. As a result fewer chlorine tablets are immersed and less chlorine is released. In this way, the rate at which the chlorine tablets dissolve is continuously adjusted to the effluent flow.

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AMERICAN MANUFACTURING COMPANY, INC.
Last revised: Feb-15-2011
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