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  1. Lan123

    AFD

    When selecting an AFD for a small motor (30 hp), would the AFDs selection depend on the make of motor or as long as the AFD is manufactured in North America (NA)it would be generally compatible with any NA manufactured pump motor? Thanks in advance
  2. Lan123

    Flexible joint on suction and discharge pipe

    Under what conditions should flexible joints(Eg. Bellow type) be provided on suction and discharge piping? I have a low lift 30 hp sewage pump application and I am curious to find out whether these are really required as I hardly see these on most of the pump applications I come across. Thanks...
  3. Lan123

    Dry pit pump

    ashtree, the current pumps are flooded suction. There are two independent suction pipes coming from wet well with isolation valves feeding each pump. I will be working with pump manufacturers to get a pump to fit the existing arrangement. The space in the can is tight but we will replace the...
  4. Lan123

    Dry pit pump

    Bimr, Fully agree about confined space. Actually we are planning to raise the controls out of the can to the grade and installed in a weatherproof enclosure. Our utility is expecting to see some land development taking place in the vicinity during the 3-5 years time and want to get the...
  5. Lan123

    Dry pit pump

    We have a old Smith and Loveless below grade "can" type duplex raw sewage pump station (20 hp each). The existing pumps are so old and therefore needs replacement. My first thought was to use dry pit close coupled submersible (By Sulzer, Xylem) but can we also consider dry pit sewage pumps...
  6. Lan123

    Max pump speed

    Good day, Is there a recommended max speed limit for positive displacement pumps used in primary sludge application. If so what is the value? We have to frequently replace the seals of our constant speed primary sludge pumps running at 350 rpm. We have experimented with different seal material...
  7. Lan123

    Coagulant Dose

    Wow bmir. another great explanation by you. Although I have seen 7.5 W/W Al2O3 never thought about 7.5 kg in 100 kg of chemical!!.
  8. Lan123

    Coagulant Dose

    ...the liquid alum that is dose at one of our treatment plants. The alum (Al2(SO4)3.18H2O ((48%) - Molecular wt. 666.132) daily dosing wt is 101.63 kg/d. If so would the Al (MW =27) daily dosing wt. be = 101.63*2*(27/666)= 8 kg/d? (factor of 2 is because 2 Moles of Al in Alum). Thanks in...
  9. Lan123

    Adjustable Frequency Drive

    ashtree and jraef thanks for the excellent responses.
  10. Lan123

    Adjustable Frequency Drives

    I am trying figure out the NPV of a AFD used with a 100 hp motor. Generally what is the lifespan of a VFD? Thanks in advance.
  11. Lan123

    Adjustable Frequency Drive

    I am trying figure out the NPV of a AFD used with a 100 hp motor. Generally what is the lifespan of a VFD? Thanks in advance.
  12. Lan123

    Activated Sludge Process

    We have a lightly loaded (BOD5 -100 mg/L) municipal extended sludge plant (1500 m3/d) that sees almost zero flows during the off peak times. (3- 5 hrs/day ). As a practice we run the RAS pumps continuously throughout the day. In order to save energy is it okay to shut off the pumps when there...
  13. Lan123

    Uniformity Coefficient (UC)

    What impact would it have if the tested UC of sand is 12% less than requested in the specifications. Effective size matched the specifications. The sand is used for a wastewater polishing bed. Thanks
  14. Lan123

    COD Removal

    Folks thanks again. After reading the comments posted here I have a clear understanding as to in what direction I should be going.
  15. Lan123

    Activated Sludge

    ashtree your reply is very interesting it sounds like you have a really good understanding of the activate sludge operations. Are you working in the operations or a wastewater process design engineer? So what you are saying is that in case the SRT is changed the system takes 2xSRT to stabilize...
  16. Lan123

    Activated Sludge

    I find that the preferred method for process control in conventional activated sludge, extended aeration, oxidation ditch systems in the MLSS control as the analysis is simple and straightforward. I am interested in hearing about the forums members experience on this topic. Are there plants that...
  17. Lan123

    COD Removal

    Thanks bimr and ashtree. We own the plant that has some excess capacity and want to accept the wastewater to make some money. based on the information provide both of you I will do some calculation to see whether it is a okay to do accept the waste or not.
  18. Lan123

    PRV question

    Thanks all. This is a for a water distribution system in rural US. Having read all the comments I now feel that it is worthwhile to use a PRV for the backup valve as well.
  19. Lan123

    PRV question

    Thanks again for all the replies. Georgeverghese You are correct. It is parallel...PRV always on duty and the second valve (Ball...) only when the PRV is out of service for maintenance. Will be a patc work for a short time until the PRV is back in service. Little Inch. I will share more...
  20. Lan123

    PRV question

    This could be a silly question. Could there be a substitute for a Pressure Reducing valve (PRV). We have to installed a PRV between two pressure zones in our distribution system. To maintain a redundancy in case of the PRV malfunctioning we want to install two PRV units side by side. I am...

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