ENCE 433                                                                                          Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS                 Spring 2001

Homework Set # 3                         Out: February 20                Due: February 27

1.                    Calculate the pH of (a) 2.00 F HCl, (b) 0.200 F HClO4, and ( c) 2.00x10-4 F HNO3

2.                  Through the consultation of general books or a search on the web, find information and write a 1-page assay (with references) on the formation, removal and possible environmental risks of ammonia on waste water.   

3.                  One nonbiological method to remove ammonia from water is to run the water through an air-stripping tower. NH3(aq) is in equilibrium with NH3(gas). However, the other form of ammonia, NH4+, is not in equilibrium with the gaseous phase and thus it can not be removed through air-stripping.

 

a)      What percentage of total ammonia (i.e., NH3 + NH4+) is present as NH3 at a pH of 7?

 

b)      Thus, in order to strip ammonia from water, to what pH must the water be adjusted to ensure efficient removal of total ammonia?

 

c)      Knowing that the form of total ammonia most toxic to aquatic life is NH3, it is toxic to several fish species at concentrations above 0.2 mg/L, justify why some wastewater discharge permits for ammonia specify that the pH of the discharge must also be less than 9.