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 |
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 |
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!
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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.