The last topic that was discussed on this blog was Phophorus (P). Next we are going to move on to the complex topic of Ammonia (NH4) and how to remove it from sewage.
The presence of nutrients in wastewater, such as nitrogen (N) has long been recognised as a source of over enrichment of receiving environments. This over enrichment can lead to explosive plant growth and algae blooms, resulting in eutrophication, fish kills etc. Therefore, the removal of these nutrients has become an everyday requirement in the treatment of sewage and other wastewaters. The aerobic removal of ammonia is a process called nitrification. This converts the ammonia (NH4) into nitrate (NO3)
As the nitrifying bacteria are generally more sensitive than the carbonaceous bacteria, the nitrification process should be designed as a separate stage or aerobic treatment, after the main BOD removal process. In regards to a package sewage treatment plant such as the BMS Blivet this means that nitrification should be designed as an additional Blivet or Aerotor stage, operating in series with the first BOD Blivet removal stage.
Average NH4 concentrations in domestic sewage influent are about 40 mg/L. However, there is a large caveat on this figure. Where water usage is less than average, concentrations can shoot up. For example, previous experience in French villages has shown inlet ammonia concentrations up to 100 mg/L!
Due to the nature of the microbes that effect nitrification, most nitrification occurs after the BOD removal or carbonaceous stages. Therefore, we must design an additional aerobic section proportional to the amount of ammonia we wish to remove. Ammonia normally requires 3 to 4 times the aerobic capacity required for BOD removal. Nitrification is also notoriously temperature sensitive. For this reason we use the ratio of 4 times BOD capacity for cold and temperate climates, and 3 times BOD capacity for warm and hot climates. In cold winter climates a combination of insulation and heating may be required to ensure the temperature of the liquor never falls below 8ºC.
Next up for discussion is some examples of calculations to work out the additional treatment capacity required for Nitrification (Ammonia (NH3 removal)
A bit about the company:
Butler Manufacturing Services is a family owned specialist manufacturer of package (all in one) products for sewage treatment and surface water treatment established in 1986 with exports to 38+ countries worldwide including the world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks/filters & vortex silt separators, chlorine contact tanks, fully fitted pumps and sumps and much more.
© Butler Manufacturing Services 2013.