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ADVANTEX'" O&VIO MANUAL C Appendix: The Nitrogen Reduction Process and Key Indicators The Process Tankage,surge capacity,application rates,and Nitrogen removal (or"nitrificationldenitrifica- loading characteristics are other design considera- tion') is a biochemical process in which ammo- dons that play a role in the sizing of the filter unit. nia is converted to nitrate (nitrification) (2NH3 Performance Indicators converts to 2NO3 +3H20) and then reduced k through bacterial action {denitrification} to nitro- To judge the nitrogen-reducing performance gen gas,which can be released harmlessly to the (°r Potential) of any wastewater treatment atmosphere. system,be sure to check the following perform- ance indicators: During the nitrification process,about 9 parts oxygen are consumed in converting 2 parts Clear, Odorless Effluent ammonia to nitrate.Therefore, depending on Simple, "see and sniff" tests can be performed J the concentration of ammonia,a considerable easily in the field. Effluent from packed bed amount of air may be needed. Other processes, filters (recirculating textile filters, recirculating like biological(BOD) reduction,may occur sand filters, intermittent sand filters) that are 1 simultaneously and further elevate the demand performing well should be clear(with turbidity for aeration,especially if the organic level is 5520 NTUst)and odorless. tl suitably high. Tests for Ammonia and Nitrate Nitrogen (DIn an abundance of air, all the aerobic or faculta- If your system is oxidizing ammonia to nitrate { tive microbes compete for their share of oxygen. (nitrifying),lab tests should measure relatively When the organic concentration is high,the low ammonia levels and relatively high nitrate J1 microbes that oxidize organic matter,primarily levels in the filtrate. Because nitrification the heterotrophic bacteria, are aggressive and responds to many and varying conditions within tend to outcompete other microbes for the avail- the aerobic treatment processes,ammonia and able free oxygen in solution.The oxidation of nitrate nitrogen levels in the filtrate are the most ammonia is accomplished by autotrophic bacte- ideal constituents to watch for any changes in ria,which do not have as aggressive of a growth performance. Start-up times can be plotted, rate,so if there isn't an abundance of oxygen, optimum recite ratios can be gauged,cleaning nitrification suffers. Consequently, the nitrifica- frequencies can be predicted,and nonvisible tion process usually lags until the organic concen- clogging or saturation detected by watching tration is depleted or until sufficient oxygen is either of these constituents. present.At a 2.5:i BODITKN ratio, the nitri- fiers may only make up about 10 percent of the BOD microbial population.At 0.5:1 BOD/TKN, the The nitrification process requires oxygen, nitrifers make up about 35 percent of the popu- which is why nitrification is enhanced when lation. BOD is extremely low. Measures of filtrate In a filtering process, the filter column must be BOD should be<15 mg/L,although higher deep enough,or the filter media must be efficient BOD may not necessarily correlate with low levels of nitrification. enough at filtering organic particles, to deplete organic concentrations to a level in which a suffi- Dissolved Oxygen tient population of nitrifiers will be sustained. Dissolved oxygen also provides critical informa- The physical (dimensional) features of the filter tion with which to diagnose how well a system will vary depending on the media's characteristics is performing. Measures of Dissolved Oxygen —void ratio, moisture holding capacity, and should be in the range of 2.5 to 6 mg/L. If the effective surface area per unit volume ratio.