Manta:  I am not sure which ...

Manta:  I am not sure which country your project is in as that may make a difference in influent concentrations. In a sewer collection system with 5 laterals 14 Km in length you would first need to calculate the HRT for your anaerobic in-situ treatment contact time and determine if that is sufficient for the anaerobic bacteria to function to degrade the organic materials--as anaerobic processes take longer than aerobic ones to degrade organics, albeit they can function with lower energy costs. If you use standard BOD and COD data for the influent municipal household flow that would be 200 BOD and 250 COD x the 120 mL/day for total organics you can estimate CFUs needed to handle these loads. Treatment in the collection system prior to arriving at a body of water or a treatment plant is a very desirable objective but somehow you would need to keep seeding bacteria since this is a "Flush Through" system and the anaerobic bacteria would need to be continuously replenished in an incubator as they wash away down the 14 Km in length. What provisions do you have for inline incubators dispersing beneficial bacteria? We have made incubators out of simple 50 gallon poly drums that have an imersion-type heater and a peristaltic pump that innoculates the wastewater and continuously dispenses live bacteria into the sewer system where is blends with the flow. Ours was in SE Asia and we had to have high strains of Nitrogen degraders as we had low flow (some non-flush sources--e.g. urinals) and as a result high NH3 concentrations from urine. Challenging project but very doable.  Another simple test would be to add a food grade dye at the beginning of the collection system and determine how long it takes to flow to the treatment works 14 Km away.