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  • Users: sjohns4
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  1. sjohns4

    Transformer Primary Voltage & Tap Changers

    I'm looking to possibly re-cover and re-use some 25 & 50 kVA single phase distribution transformers. We're a primary power customer on a 13.2kV / 7.6 kV system. The transformers are name plate 13200GRDY / 7600 HV and have 2x2.5% taps over and below nameplate. By my math, with the tap changer at...
  2. sjohns4

    Extreme Flow Variations & Process

    I'm preparing a PER for a training facility that sees incredibly variable flows. The variation will happen weekly. There can be intermittent periods of extremely high flows (~140,000 GPD) flowed by periods of extremely low flows (~8,000 GPD), and various levels between. I'm using 350 mg/l BOD &...
  3. sjohns4

    EPDM Membrane Diffuser Life?

    What sort of life span is typical for EPDM tube type membrane diffusers in municipal wastewater treatment plant applications? Thanks, Mike
  4. sjohns4

    IEC conductor and overcurrent protection sizing criteria?

    I'm working with a volunteer organization to provide training to a group of engineers in Rwanda. Their primary focus is to provide drinking water, but as most of us water people have had to learn along the way you need electricity to turn the pump. It's been well documented, and I observed...
  5. sjohns4

    Single Phase Inrush & Generator?

    I'm working on a water supply project in Haiti. The pipes, pump, and tank are the easy parts. Our power source is going to be limited to a portable generator that operates 2-3 hours every couple of days. The submersible well pump I've selected is a of European manufacturer with approximately a...
  6. sjohns4

    Wet Well Floats & Rags?

    Hi All, I'm working with a municipality who has a few typical submersible wastewater pump stations that have ragging problems. The controls use good old-fashioned relay logic with float switches. These stations have very bad ragging problems. We have plans for a grinder at the upstream station...
  7. sjohns4

    2009 IECC Insulation Values

    Can someone tell me what the required wall and celling insulation values are according to the 2009 IECC code? I'm designing a wastewater pump station building (+-930 sf floor area). I've got a copy of the code ordered but would like to discuss insulation & wall details in a meeting this...
  8. sjohns4

    Sand filters after WW ponds?

    Hi all, I have a small wastewater treatment systm I've been working with on and off for a while now. The The existing system is an aerated lagoon with two manually alternated, shallow, non-aerated settling ponds prior to chlor/de-chlor and surface discharge. The reciving stream recently got hit...
  9. sjohns4

    Hydraulic Content Concrete?

    I'm looking at a municipalitie's specifications for concrete to be used in a wastewtaer pump station wet well design. They require "Hydraulic Content Concrete". What exactly is that? I was thinking it may be a concrete mix with a water proofing admixture like Xypex or Penetron, but wasnt sure...
  10. sjohns4

    Battery Charging

    1) Can a basic unregulated DC power supply be used for battery charging (lead-acid type)? 2) is there a rule of thumb or formula to size the current output of the power supply to maintain a battery at or near full charge without over-charging?
  11. sjohns4

    Pump solids handling capacity behind a grinder?

    I'm looking at a fairly high head wastewater pumping application for a realitively small flow (~350 GPM @ 365' TDH). I can find traditional solids handling pumps that would work connected in series. However, given the pump station is collecting flow from an entire small town I'm thinking a bar...
  12. sjohns4

    Can control relays be wired in series?

    Hi guys, I'm working with a municipalitiy to bring a couple pump stations up to good working order. They are fairly simple operating stations and the control is going to be with an alternator and plug-in type 120V relays. My basic question is can two relay coils be wired in series? What about a...
  13. sjohns4

    Applicable Reinforced Concrete Design Standards

    My primary area of practice is water & wastewater distribution, treatment, collection, etc. Within in this field, there is quite a bit of reinforced concrete design & construction: Typically building foundations concrete slabs, and concrete tanks. I don't know that I want to make a career...
  14. sjohns4

    HDD Pipe and Casing Q's?

    A municipality I'm working with to design a developer funded system is requiring a casing to be drilled under a creek then a carrier pipe to be slid through, both HDPE. I've had many HDPE pipelines installed by HDD method, but never did a casing / carrier - it just seems overkill to me...
  15. sjohns4

    Dissolved Oxygen Meter Accuracy?

    We've got fairly new brand X on-line DO monitors at a wastewater treatment facility. We've got a new brand Y hand held DO monitor at the same plant. The two never read the same, off from 0.5 to 1.0 mg/l. You can calibrate both to a zero solution, but brand X has no other calibration. Our...
  16. sjohns4

    Odors from bar screen?

    I'm looking at installing a bar screen & washing compactor in front of a ~2.5 MGD pump station. My concern is the odors from the solids may get prety offensive. Has anyone used things that will minimize this, such as sealed bags on the end of the compactor? Thoughts welcomed... Thanks, Mike
  17. sjohns4

    Peroxide for Algae Control?

    I'm working with a cash-strapped client to bring their treatment lagoons back into compliance. Part of the problem, due to the reduction in flow from the facility, is the long HRT in the lagoons. The first pond is aerated, so I'm hoping we can come up with a small blower & diffuser arrangement...
  18. sjohns4

    Lagoon Liner

    I'm doing an evaluation of an existing wastewater treatment lagoon. The liner is visibally torn above the water line so I'm going to recommend and budget replacement. What type of material would you use? THe state regs just say minimim 60 mil thickness. Thanks, Mike
  19. sjohns4

    4-way valve at cross connection?

    I've got a new sludge press which requires a wash water connection. Normally the press will use the plant's non-potable water supply. However, I've also provided a potable water connection should the non-potable supply fail due to pumps, plant upset, etc. I have an RPZ installed on the potable...
  20. sjohns4

    Quick & Dirty Digester Sizing

    I'm doing some preliminary planning and evaluation for an anaerobic digester at an existing WWTP. The plant design flow is 8 MGD and treats almost entirely domestic flow with nothing too exotic. Are there any rules of thumb to come up with a tank volume / footprint that could be used to get me...

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