WASTEWATER TREATMENT PLANT PROCESS DESIGN
by Vernon Smokey Stack, P.E., D.E.E.

The information in this web site is directed to environmental engineers (young or old) who might need help with conceptual design of wastewater treatment plants. The objective is to provide: 

·        Information that may be helpful

·        Useful tools

·        Old tricks (hopefully updated) and new tricks suggested

·        Guidance intended to improve the quality of the product

·        Input that may help the engineer reduce risks. 

INFORMATION THAT MAY HELP

The engineer needs a basis for his design.  The usual stuff:

·        Quantity of flow

·        Occurrence of high flows

·        Biodegradable organic load

·        Peak organic load

·        Effluent requirements

·        If nitrification/denitrification is required

o       TKN load

The engineer fits a process between influent wastewater load and the effluent requirements using available information that may be limited or of poor quality.  Ideas on how to check (or adjust) the available data are offered. 

USEFUL TOOLS

A relatively simple Activated Sludge Mathematical Model is provided.  It is a convenient ways to estimate:

·        Carbonaceous Performance

o       Effluent Quality

o       Oxygen requirements

o       Sludge production

·        Nitrification Reactions

o       Oxygen requirements

o       Nitrates generated

o       Nitrification safety factor

·        Denitrification

o       BOD removed

o       Nitrates removed

The model can be applied to Flow-Through, SBR, Oxidation Ditch, and BNR designs.  It will add solids to the process to account for solids generated during phosphorus removal, through biological phosphorus removal, ferric precipitation, or alum precipitation.   

OLD TRICKS AND NEW TRICKS?

·        How much excess sludge does an activated sludge produce?  It can be a tricky subject.  You can use textbook information, but (a warning) you may be lead to the wrong answer.   The model does it for you.  Alternatively, an Excell spreadsheet is provided that can help with understanding and estimating sludge production.

·        BOD₅ measurement provides semi-quantitative information.  The fact that biochemical oxygen demand became a legal parameter has been detrimental to the Environmental Engineering Profession.  The mandatory information has little engineering value.  How do you cope with it?  Is there something better? 

GUIDANCE INTENDED TO IMPROVE 
THE QUALITY OF THE PRODUCT

·        The engineer's objective is to meet the client’s needs while striving to minimize construction cost and operating cost where feasible.

o       What process choices best meets the objective?

o       What is a reasonable safety factor?

o       What kind and degree of monitoring aid does the operator need?

              These are good questions, and I hope to present a few thoughts.

INPUT THAT MAY HELP THE ENGINEER REDUCE RISKS

   An engineering result is the culmination of the Engineer’s knowledge, experience, and professional judgment.  He is at risk for bad judgment.  Occasionally, the Engineer needs the support of Vendor Engineering.  To reduce risks to the project (and the Engineer), the Engineer must be able to check engineering offered by a Vendor.  A miscalculation by a Vendor is the responsibility of the Engineer (in a court of law).  Hopefully, some of the "Tools" offered will help the Engineer reduce risks.

   These "Tools" are those that I have developed for personal use through the years, and like most Engineering Stuff, new information develops, and "Tool" need upgrading.  I have attempted to keep the "Tools" up to date, but you will find that I am still using English units.  These "Tools" are not superior; they are "Tools" that I am comfortable with and find useful.  If you elect to try them, please apply  good judgment.  I think the "Tools" work well, but I developed them and probably take a lot for granted.  If you find a problem with A "Tool" please let me know.  You may find them limited and cumbersome, but I also hope that you find some value.

   The pdf files will open with Adobe Acrobat 5.0 or higher. 

smokeystack@comcast.net