Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification Dale Adams, P.E Managing Engineer, Colorado Springs Utilities September 8, 2015

Slide 21/16/2015 Electricity | Natural Gas | Water | Wastewater Background Nitrogen Removal Phosphorous Removal Benchtop fermentation of whey Full scale design Problems with start-up Adding Whey for Denitrification Agenda

Slide 31/16/2015 Electricity | Natural Gas | Water | Wastewater Whey is a by-product of cottage cheese production A Dairy approached Colorado Springs Utilities to say they would find a way to dispose of whey to avoid BOD surcharge Utilities analyzed the whey – thought to be a good source of carbon JDPWRRF was limited on carbon for its biological treatment processes Plant effluent pH was too low – had to add sodium hydroxide to raise effluent pH - $100K per year Adding Whey for Denitrification Background

Slide 41/16/2015 Electricity | Natural Gas | Water | Wastewater Temporary tanks were installed in 2009 and the dairy trucked cottage cheese whey to fill the tanks During the pilot project whey was dosed to the inlet of the primary sedimentation tanks As winter approached, the decision was made to move the whey operation into a spare grit tank to keep the whey from freezing and use the grit tank pump to dose the whey This allowed a larger inventory to be maintained and some fermentation occurred Adding Whey for Denitrification Background

Slide 51/16/2015 Electricity | Natural Gas | Water | Wastewater Ammonia conversion to nitrogen gas is a multi-step biologically driven process One set of bacteria (nitrifiers) takes ammonia to nitrite then to nitrate under aerobic conditions (lots of air is blown into the basins to give the bacteria oxygen) Another set of bacteria (denitrifiers) take nitrate to nitrite under anoxic conditions (very low oxygen) and then to nitrogen gas which goes to the atmosphere; requires CARBON for this step The conversion of nitrate to nitrogen gas adds alkalinity back into the wastewater – raising the plant’s effluent pH Adding Whey for Denitrification Nitrogen Removal

Slide 61/16/2015 Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification

Slide 71/16/2015 Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification

Slide 81/16/2015 Electricity | Natural Gas | Water | Wastewater Was not occurring at JDPWRRF very much prior to whey addition Biological P removal requires several things: First an anaerobic zone is needed (no oxygen) Second, volatile fatty acids need to be present Under these conditions bacteria dump phosphorous and store the VFA as energy Under subsequent aerobic conditions, bacteria take up twice as much phosphorous Adding Whey for Denitrification Phosphorus Removal

Slide 91/16/2015 Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification

Slide 101/16/2015 Electricity | Natural Gas | Water | Wastewater Set up a reactor Fed it fresh whey at a rate that controlled the hydraulic residence time Temperature was maintained at 94 F – the temp that we receive cottage cheese whey from the dairy pH was maintained at VFAs were analyzed to see what was happening with fermentation Adding Whey for Denitrification Benchtop Fermentation Experiments

Slide 111/16/2015 Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification

Slide 121/16/2015 Electricity | Natural Gas | Water | Wastewater Adding Whey for Denitrification

Slide 131/16/2015 Electricity | Natural Gas | Water | Wastewater Whey is very a very dilute source of carbon Adding Whey for Denitrification Design of Full-scale Carbon Facilities

Slide 141/16/2015 Electricity | Natural Gas | Water | Wastewater Dairy may not stay in the cottage cheese business Need to design for flexibility Tanks were designed to handle whey, primary sludge, and acetic acid (could not make them compatible for methanol) Adding Whey for Denitrification Design of Full-scale Carbon Facilities

Slide 151/16/2015 Electricity | Natural Gas | Water | Wastewater Design for Handling Whey Two tanks, each 35,000 gallons Telescoping valves for scum removal Mixer in main chamber under fermentation mode Connection from tank headspace to odor control ductwork in existing PSTs Special coatings systems to withstand a variety of chemical action Waterproofing membrane on outside

Slide 161/16/2015 Process Schematic Mixers Future Mixers Future PS Screens pH Control Pumps Feed Pumps Tank Drain/Future PS Recirc. Pumps Pumps Telescoping Valves Control Valves and Flow Meters

Slide 171/16/2015 Electricity | Natural Gas | Water | Wastewater Primary sludge fermentation Up to two more tanks, each 35,000 gallons Combination submersible tank drain/future PS recirculation pumps to be used Additional mixers will be installed FRP baffles will be installed

Slide 181/16/2015 Electricity | Natural Gas | Water | Wastewater Start-up Problems Started up the whey tanks with pH control set at 5 Shortly after start-up ground settlement broke the feed piping – 20 foot deep excavation and repair was completed After the repair bio-P and nitrogen removal have not responded like we saw during the pilot project The dose location is different than during the pilot project We have not had time yet to do a deep dive into why the system is not performing as expected