(Lift Stations) Ventilation
Ventilation and heating are required if the lift station includes an area routinely entered by personnel. Ventilation is particularly important to prevent the collection of toxic and/or explosive gases. According to the Nation Fire Protection Association (NFPA) Section 820, all continuous ventilation systems should be fitted with flow detection devices connected to alarm systems to indicate ventilation system failure.
Dry-well ventilation codes typically require six continuous air changes per hour or 30 intermittent air changes per hour. Wet-wells typically require 12 continuous air changes per hour or 60 intermittent air changes per hour.
Motor control center (MCC) rooms should have a ventilation system adequate to provide six air changes per hour and should be air conditioned to between 13 and 32 degrees Celsius (55 to 90 degrees F). If the control room is combined with an MCC room, the temperature should not exceed 30 degrees C or 85 degrees F. All other spaces should be designed for 12 air changes per hour. The minimum temperature should be 13 degrees C (55 degrees F) whenever chemicals are stored or used.
Odor control is frequently required for lift stations. Four major ways to control odors are chemical addition, air injection, carbon adsorption, and biofilters. Another relatively simple and widely used odor control alternative is minimizing wet-well turbulence. Chemicals typically used for odor control include chlorine, hydrogen peroxide, metal salts (ferric chloride and ferrous sulfate) oxygen, air, and potassium permanganate. Chemicals should be closely monitored to avoid affecting downstream treatment processes, such as extended aeration. Scrubber and biofilters are a more expensive form of odor control. Air injection is less effective than the other methods. If odorous compounds are present at the point of air injection, they will diffuse in dissolved air and escape to the atmosphere. This can sometimes worsen the odor. Also, depending on the amount of air injected, turbulence can release odors and make the problem with odors even worse.
Using the lbs formula
What is the chlorine feed rate per day to a lift station for a flow of 2,800,000 gal with a dose rate of 17 mg/L?
Since the feed rate in lbs is required, use the numbers provided and place them in the lbs formula. First convert gallons into MGD.
(2,800,000 gallons) / (1,000,000) = 2,800, 000 = 2.8 MGD
Lbs = 2.8 MGD x 8.34 x 17 mg/L = 397 lbs
Calculate the chlorine dosage in a lift station
A lift station pumps 1.4 MGD of wastewater per day. The water contains an average of 330 lbs of solids. How much chlorine in mg/L would be needed for keeping this system fresh?
Using the lbs formula find out the amount chlorine needed.
Concentration = (330 lbs) / (8.34 lb/gal x 1.4 MGD)
Concentration = 28.26 mg/L of chlorine
The reliability of power for the pump motor drives is a basic design consideration. Commonly used methods of emergency power supply include electric power feed from two independent power distribution lines; an on-site standby generator; an adequate portable generator with quick connection; a stand-by engine driven pump; ready access to a suitable portable pumping unit and appropriate connections; and availability of an adequate holding facility for wastewater storage upstream of the lift station. Critical pumping stations are often equipped with diesel generator to provide power to critical equipment in the event of a blackout or loss of electricity.