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NewsroomTroubleshooting Lagoons

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Even well-designed lagoons sometimes turn sour. EBH can analyze your past records, conduct additional testing, and come up with low-headache solutions. One of the simplest and most fool-proof solutions is to build a wetlands cell to go non-discharging, if site conditions are right. We’ll go into more detail on wetlands cell design in future blogs. Here is a list of common problems we’ve seen and possible causes:

Issue Possible Causes
Rotten Egg Odor Inadequate Aeration, Sulfur-Reducing Bacteria, Pond Overloading, or Pond Turnover
Corrosion of Steel and Concrete in Enclosed Spaces Hydrogen Sulfide Production and Oxidation to Sulfuric Acid, long detention time in force main with anaerobic sewage
Plugged Pipes Pipes submerged in sludge, insufficient screening at headworks, turtles, grease
Dark pond with little wave action Not enough air, grease on surface calming waves, tall trees next to pond, ponds designed without considering wind direction, pond overloaded
Dike Erosion Slope designed too steep or too sandy, not enough slope protection
Pond Turnover Pond overloaded, denitrification in sludge layer, cold autumn rains, warm sludge layer rising in early spring
Algae Bloom High concentrations of nitrogen and phosphorus, geese, long sunny summer days
High BOD or Fecal Coliform in Effluent Not enough HRT, Ineffective use of pond volume, sludge in effluent, not enough air, geese
High TSS in Effluent Algae Bloom, Sludge in Effluent
High Ammonia in Effluent Not enough Air, Not enough HRT, Low temperatures, Release of ammonia from sludge layer, Low pH
Sludge in Effluent Drawoff point too low, sludge buildup, pond turnover
Solar powered aerator installation

Solar powered aerator installation

One solution that can solve a lot of problems is adding more air to a lagoon. This helps encourage the activity of aerobic bacteria, speed up pond recovery after a turnover, thin the sludge layer, oxidize smelly sulfides to odorless sulfates, convert the organic carbon in volatile suspended solids (VSS) to carbon dioxide gas, lower effluent BOD, convert ammonia to nitrate, kill E. Coli, and decrease the amount of algae in a pond. Every aerator has its own pros and cons, and the right aerator for you may not be the right aerator for someone else.

 

Type of Aerator Pros Cons
Wind and waves Free Not reliable, can be blocked by hills or trees
Coarse bubble Diffuser Simple, little concern with clogging Only 5-10% Oxygen Transfer Efficiency (OTE)
Microbubble Diffuser Approx. 30 to 50% OTE Higher Cost
Nanobubble Diffuser Approx. 90% OTE High Cost, Patented Process
Oxygen Infuser 90% OTE, low concern with clogging Higher equipment cost, more maintenance
SolarBee No external power required, good for chemical mixing, keep ponds from stratifying Each aerator adds only a small amount of oxygen
Venturi Nozzle Simple, no concern with clogging, good for recirculating Coarse bubbles, low OTE
Cascade Aerator Help off-gas ammonia and carbon dioxide Low OTE
Sodium or Calcium Nitrate Easy to apply Chemical cost, adding a source of nitrogen that may be hard to remove later

Wave action on a very windy day

 

Adding air will almost always help, but oxygen is only one facet of the complex chemical and biological processes going on in a lagoon. We’ll get deeper into the science of designing and operating lagoons in future blogs!

Article Written by:
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    Richard Ammel, PE

Richard Ammel, PE, EBH Engineer, is a licensed professional engineer who has designed and inspected the construction of sewers, pump stations, and wastewater treatment systems for several small towns in Kansas. He received his Bachelor of Science (B.S.), Civil Engineering degree from Colorado School of Mines. Contact Richard if you would like to discuss your municipality’s waste water treatment challenges at 620-793-8411.