Liquid Polymer Feed Problem solution

Let's reason out this one.  How many gallons would be 1 ppm for a 5MGD flow?  5gallons in 5 million gallons is one ppm, RIGHT?  So half that would be 0.5 ppm.  So, 2.5 gallons of liquid polymer in a 5 million gallon daily flow will be a 0.5 ppm dosage.

If 2.5 gallons are used each day then 55gallons (1 drum)/2.5 gallons per day will give us the number of days the drum will last.  The drum will last 22 days.

Did you get this answer?  Bill

Feeding liquid polymer

Many water treatment plants use liquid polymers for coagulation or filter aids.  The liquid polymer is delivered in drums and often the polymer is fed directly from the drum using a chemical feed pump.  Most operators calculate the dosage based on the amount of liquid fed into the water flow.  In other words, the liquid polymer in the drum is considered 100% strength.  This is convenient for keeping track of the volume used so that the necessary inventory is kept on hand.

Example problem:  A treatment plant is processing 5 MGD.  It is using a liquid polymer as a filter aid and this chemical is being fed to the filter influent so the entire flow is treated.  The filter aid dosage is 0.5 ppm.  How many gallons of filter aid are used each day?  How long will a 55 gal drum last?

Work on this and I'll give the solution in the next post.

Bill

Solution to Slug Method Disinfection Problem

Ok, were you able to solve this problem?

The pipeline to be chlorinated is 6in diameter and 800 ft long.

The pipeline volume per foot is 3.14 x .25 x .25 x 1 ft x 7.48 gal/ft = 1.47 gallons/ft of pipeline

To disinfect the pipeline we want a 100 mg/L chlorine dosage in contact for 3 hours.

We want to finish the job in less than 8 hours so we will need a slug that is about 40% of the entire volume.

A 40% slug is 800 ft x .4 = 320 ft

The volume of the slug is 320 ft x 1.47 gallons/ft = 470 gallons

The withdrawal rate is 470 gallons/180 min = 2.6 gpm

The amount of 1% sodium hypochlorite needed to make 470 gallons of 100 mg/L solution is
470*100 = x*10000   or 4.7 gallons

Chlorinate the valves and hydrants with a calcium hypochlorite tablet each.


Did you get the correct answer?
Bill

Pipeline disinfection by slug method

Pipeline Disinfection Slug Method Description

 

The slug method of pipeline disinfection requires that a section of new main is highly chlorinated, then valves are operated and water is slowly removed from the end of the main causing the “slug” of highly chlorinated water to move along the newly installed pipeline.  As this slug passes tees, crosses, and hydrants, the adjacent valves are operated to ensure the disinfection of all appurtenances and branches.

 

Example Calculation

Using the slug method chlorinate a 800 ft length of 6 in diameter pipeline.  There are 4 fire hydrants and two valves located on the new section of pipeline.  The chlorination must be completed in less than 8 hours.  A 1% sodium hypochlorite solution is used for this procedure.  How much is needed and describe the process.

 

I'll give you a couple of days before I reveal the answer.

Bill

Welcome water operators looking for help

This is a help site for water system operators, supervisors, or other drinking water system professionals looking for some help with your technical questions.  I will try to answer your questions or direct you to resources for the information you are seeking. 

This site is just getting started so please be patient.  I am building the site so as time passes you will find more information. 

Thanks for visiting and check back to see how the site has changed.


Bill Lauer

By the way, there is no fee for the information provided on this site.  I'll do my best to give accurate, correct answers, but be advised that you must combine this information with local and site-specific circumstances and make your own decision regarding any actions.  It is your responsibility to satisfy all regulatory requirements and for any actions you take.