TABLE 3.

N conversion rates, NO₂⁻/NH₃ ratios, and N loss in 2-liter reactors^a

No. of N. eutropha cells (ml−1)	Conversion rates (μmol reactor−1 h−1)					NO2−/NH3 ratio	Sp act (μmol of NH4+ g of protein−1 h−1)
	Ammonia	Nitrite	NO2b	NO	Nitrate		B. anammoxidansc	N. eutrophad
0e	141.4	187.9	0	0.01	36.8	1.33	4,423
107	149.9	191.4	14.4	13.5	38.1	1.28	4,579	1,080
5 × 107	183.8	183.2	70.6	71.2	41.3	1.00	4,963	1,462
108	226.2	185.8	129.4	119.1	49.3	0.82	5,525	1,545

^aThe reactor with the anammox biomass was supplemented with 0, 10⁷, 5 × 10⁷, or 10⁸ N. eutropha cells ml⁻¹. The consumption and production rates were calculated on the basis of the substrates added to the reactor and the products leaving the reactor. The standard deviation for five replicate experiments was less than ± 5%.

^bIn sterile control experiments, the NO₂ consumption resulting from the reaction of NO₂ with water was determined. The values obtained were subtracted from the data obtained with cells.

^cThe specific ammonia oxidation activity of B. anammoxidans was calculated on the basis of nitrate production.

^dThe specific ammonia oxidation activity of N. eutropha was calculated on the basis of NO₂ consumption and NO production.

^eThe anammox biomass contained about 2 × 10³ Nitrosomonas cells ml⁻¹.