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Wastewater Recycling: Practical Approaches for Success

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Outline

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  • Why Recycle
  • Top Considerations
  • Equipment Tips
  • System Examples
  • Focus = reuse of effluent water and practical approaches/tips

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Why- Cost of Water

Water and wastewater rates are rising

Cost of utility upgrades are being passed on to customers

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Why - Stewardship

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Why- Public Perception

“The problem is what they’re doing there: They’re boiling vats of toxic metal-water solution.”

JANE WILLIAMS, EXECUTIVE DIRECTOR OF CALIFORNIA COMMUNITIES AGAINST TOXICS. Calmatters.org

"When companies are directly impacting downstream water and impacting health, I think the onus is on them to take action as fast as possible to stop ongoing contamination," said David Andrews, a senior scientist at the Environmental Work Group. Mlive.com.

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Top Considerations

  • Engage Quality/Production early
  • Easy wins
  • Do you need 100% Reuse
  • Biology
  • Manage rinse rates
  • Rinses as tank makeup
  • Recycle to easy baths

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Engage Quality/Production Early�

  • Quality and on-time production is key
  • Bath quality is critical to success
  • Include chemical supplier and internal QA/QC or production staff to ensure proper water quality
  • Don’t solve one problem making another!

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Easy wins = require little investment�

  • Maintain the operation of your recovery units
  • Counter Flowing Rinses
  • Minimize Drag out- Hang time, Splash Mats, How parts are hung
  • Boilers:
    • RO Feed- to increase cycles
    • Condensate- Monitor with a conductivity probe and reuse
  • Cooling towers:
    • Use towers instead of “once through” cooling
    • Use RO feed to increase cycles
  • Seek Evaporation credits
    • Wastewater fees should cover only the water discharged. NOT lost to evaporation.

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Do you need 100% reuse?�

  • The water/wastewater rates in the Midwest are inexpensive on a national scale.
  • Return on Investment must be met
  • Put together a budget based on water spend and a goal of reduction.
  • Oftentimes a goal of 50-75% is more realistic
  • Program must have an exit mechanism for solids

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Biology�

  • Wastewater has what bacteria/fungus wants:
    • Warmth
    • Food
    • Place to live
  • Disinfection should be part of any reuse program
  • Methods can include:
    • Ultraviolet Light
    • Peroxide
    • Non-oxidizing biocides

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Biology Testing

  • Testing for biology should be done regularly
  • Using dip slides or combo BARTS will help you gauge your program.
  • Failure to test and control will cause problems in membranes/filters/sand/or your bath.

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Rinse rates�

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Rinses as tank makeup�

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Recycle to easy baths�

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Equipment Review

  • Resins
  • Membrane Filtration
  • Evaporation
  • Ultraviolet Lamps
  • Filtration

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Deionization (DI) or Resins

  • Useful upstream (recovery units etc.) of wastewater to minimize wastewater volume
  • Will remove total dissolved solids (TDS) from effluent allowing for low TDS reuse
  • Not all baths require low TDS
  • Must be either regenerated onsite (creating wastewater) or sent offsite for regeneration
  • Resin is expensive: and
    • Should be protected from fouling by good filtration
    • Must be weighed against the ROI goals

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Membrane Filtration

  • Reverse Osmosis (RO) is a key method for large scale TDS improvement
  • Key points to be aware of:
    • Requires pretreatment to prevent fouling and scaling
    • Excess iron or aluminum should be mitigated
    • Will require regular clean in place (CIP) processed and should be budgeted for
    • Contaminants will become concentrated 2-4x in the reject. Ex. 0.75ppm zinc could be 3ppm in the reject.

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Evaporation

Evaporators are useful to:

Achieve 0% liquid discharge- ex. evaporate the reject from reverse osmosis

Mitigate difficult waste streams that would make reuse or wastewater difficult

Include:

Atmospheric

Steam or natural gas heated

Key Costs:

Natural gas

Power

Concentrated sludge haul off

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Ultraviolet Light

  • Used to disinfect/sterilize reuse water to prevent microbial growth
  • Commonly put on a recirculation loop on a storage tank
  • Key Benefits:
    • No chemical input
    • No chemical residuals
  • Key Tips:
    • Is not persistent
    • Requires clean tubes to transmit the UV
    • Works poorly if the water is turbid

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Filtration

Bag Filters

  • Pros:
    • Simple
    • Inexpensive to purchase
    • Easy to change micron of bags
  • Cons:
    • Ongoing expense of bags
    • Will your staff change the bags

Sand Filters

  • Pros:
    • Effective filtration
    • Low labor
  • Cons:
    • Expensive to buy
    • More maintenance if sand is fouled
    • Generates backwash water

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System Example A

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System Example B

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Summary

  • Reuse:
    • Saves money
    • Good stewardship
    • Good PR
  • Make goals:
    • Consider a mid point goal rather than 100%
    • Engage all stakeholders
    • Reuse is more difficult than using city water
  • Plan for the baths where reuse water will make sense
    • Consider non-critical rinses and tanks
  • Plan for a solids exit:
    • RO reject
    • Evaporation
  • Keep up with biology
    • Test for biology and control it
  • Plan for your equipment:
    • Plan for resin regen or offsite
    • Plan for cleaning and maintaining your RO membrane
    • Choose the filtration that your staff will maintain

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Questions�