Question

Ammonical nitrogen in wastewaters is a measure of NH3 and NH4+. Ammonia from wastewaters can be removed by air stripping. What is the pH that needs to be maintained so that 90% of ammonia can be removed with minimal air stripping?
Kb = 1.8 x 10-5 for NH3 => NH4+ + OH-.

Answer 1

Answer:

There are various methods for removing ammoniacal nitrogen from solution, including

physical, electronic, and biological methods. Ammonia stripping is a particularly efficient

method for ammonia recovery from high concentration wastewater [6,7], In ammonia

stripping system, ammoniacal nitrogen is removed as a gas by supplying gas such as air

or steam [6–9]. The reactor is usually a fixed-bed column or packed bed tower [6–9]. In

tower-type reactors, ammonia mass transfer is achieved by gas-liquid contact within the

packing material [10]. Therefore, the liquid-gas ratio should be carefully considered to

optimize the operating conditions of packed towers.

In this regard, substantial research and development have focused on the operating

conditions and other factors affecting stripping towers for different types of wastewater [11–16]. For example, Ferraz et al. [12] performed ammonia stripping from landfill leachate using a packed tower at room temperature and pH 11 and achieved a removal efficiency of 98% after 24 h of stripping at a liquid-gas ratio (L/G) of 6.7–20 L/m3

.

Guštin et al. [13] used a continuous flow packed tower to strip ammoniacal nitrogen from

anaerobic digestate at a liquid-gas ratio of 2.5 L/m3

, achieving a removal efficiency of 55%

at 50 ◦C and pH 10. Liu et al. [14] evaluated the ammonia removal efficiency and rate

Appl. Sci. 2021, 11, 441.

Appl. Sci. 2021, 11, 441 2 of 13

for the urine with temperature, pH, concentration, and liquid-gas ratio. Zhu et al. [15]

and Li et al. [16] also analyzed ammonia removal rate by temperature, pH and air supply

condition.