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Recent content by ccor

  1. ccor

    Ion exchange for ammonia removal in drinking water

    I agree that conversion to chloramines could be cheaper from a chemical addition standpoint. However, CT is difficult to achieve with combined chlorine, typically requiring a 400 - 500% increase in clearwell size. I have only heard of one system that uses it for primary disinfection and its...
  2. ccor

    Ion exchange for ammonia removal in drinking water

    Consider using breakpoint chlorination by adding another chlorination point upstream of the filters (assuming they are not biological filters). Dose this point past the “breakpoint” where you just start to see a free-chlorine residual. This will not count towards your CT so the rest of the...
  3. ccor

    DIP vs. HDPE?

    I ran into this same issue when I worked in Steamboat Springs. We were able to spec HDPE in some out-of-service-area developments (in-service-areas were required to have a minimum dia. of 6" for fire flow) and it has been working well with the longest in-place time of only about 5-years...
  4. ccor

    Gravity flow velocity into MH?

    The projects I have done this on, the price has been a wash or slightly cheaper. This is because: the larger pipe diameter is offset by the thinner wall, the manholes are offset by the elimination of restraint and air release station (also frost line is about 7' here so depth of excavation was...
  5. ccor

    Wastewater Treatment & Disposal Solution- Small but Growing Community

    My guess is you will receive a lot of varying opinions on this, but my two cents: 140 SFUs is too large for the proposed and approved treatment options. There may only be ten homes now, but now is the time to get it right before it is too late. I vote for the centralized WWTP. It will likely...
  6. ccor

    Gravity flow velocity into MH?

    Layouts that have the last section of forcemain going downhill can be really problematic. If the steady state gravity flow velocity is higher than the pumping velocity the water column can separate which can rapidly change the pumping head causing the pump to "search" for steady state. Of...
  7. ccor

    Refurb of Slow Sand Filters

    Usually a finer sand is used, with an effective size of 0.25-0.35mm (D10) and a uniformity coefficient of 2 - 3, and specific gravity > 2.6. Depth is usually 1-1.5 m. When maximum allowable headloss occurs (20-30 days) the top 1 - 2 cm is scraped off and stockpiled on site. This is repeated...
  8. ccor

    How to calculate Carbon Usage Rate

    Yes the method uses laws of similitude to scale down the governing transport equations. Water Treatment: Principles and Design by MWH (2005) has a decent section on RSSCT design written by John Crittenden one of the original developers of the RSSCT method. Its a good reference if you do a lot...
  9. ccor

    How to calculate Carbon Usage Rate

    You've done all you can do, and you're right the calculations are basically worthless. The Fruendlich isotherms are determined with DI water and a single compound. Bed life is usually controlled by the NOM in the system, but since all NOM is different there is no way to do the calcs based on...
  10. ccor

    Hydraulic Capacity of Back pitched pipes

    RWF has the right idea but I don't know that HEC-RAS would be very efficient. Basically a pipe with an adverse slope has no gravity flow capacity. This means that the pipe must flow under pressure, where capacity is determined by definition. Usually keeping the HGL below ground level to avoid...
  11. ccor

    Flow into submerged Grate Inlet

    UDFCD is a multi-jurisdictional drainage agency in the metro Denver area and I find their manuals are quite good. Check out Volume 1, Chapter 6, Section 3 which covers this subject quite thoroughly. You can also find design spreadsheets on the website which may be of help...
  12. ccor

    Non-negligent E&O Limitations vs Betterment

    You have no legal obligation to pay. Engineers are not required to be mistake free, only to meet the standard of care. Besides, had you called it out correctly on the plans the owner would have had to pay for it in the original contract, its a cost of doing the project not of your mistake. If...
  13. ccor

    Flow Through a Flat Channel

    For a horizontal channel flow only occurs if there is a difference in head across the channel section. You will need to calculate the water surface elevation at the downstream control section. Then compute the water surface upstream using the standard step or direct step calculations. These...
  14. ccor

    Detention Basin Using Rational

    The FAA outlined a procedure in "Airport Drainage," 1970. http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/f26314836c9a516a86256c750060f2fe?OpenDocument Easy to code into a spreadsheet, and pretty good results.
  15. ccor

    inconvenient truth- errors?

    Beyond the rhetoric and politicalese, the facts are these: 1) increased CO2 concentrations in the atmosphere increase the heat retained in the atmosphere 2) burning fossil fuels releases amounts of CO2 to the atmosphere beyond that which would naturally occur 3) the earth has some finite...
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