Removal of ammonia from wastewater by ion exchange in the presence of organic compounds
Thesis DisciplineChemical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
The aim of the work described in this thesis was to study the removal of ammonium ions from water by ion exchange. The classical technique is to use biological nitrification and denitrification to convert ammonia into nitrogen gas. Removal by ion exchange offers a number of advantages, such as the ability to handle shock loadings and to polish water to a very high specification. The ion exchanger used in this project was clinoptilolite, a naturally occurring zeolite. Previous research has included characterisation of clinoptilolite, the effect of other common cations on uptake, biological regeneration, and a few other studies. A comparison with other exchangers was also conducted. Much of the available literature is concerned with clinoptilolite and occasionally with mordenite, however modern ion exchangers are polymer based. Two polymeric ion exchangers (Dowex 50w-x8, and Purolite MN500) were evaluated in this project. The main scope of this thesis was to look at the effect that organic pollutants has on ammonium ion removal during ion exchange. The results of batch equilibrations of NH4+ and the three exchanger resins can be seen in chapter 4.0. They show that the presence of an organic compound enhanced the uptake of NH4+ in most cases onto clinoptilolite and Purolite MN500. There was no apparent uptake onto Dowex 50w-x8. Further experiments with a sample of real industrial wastewater (woolscour wastewater) showed varied results, showing that each site should carry out its own pilot scale testing during plant design. Other experimental work showed that the exchanger resins adsorb little or none of the organic compounds in solution. These results can be seen in chapter 5.0. ii Removal of ammonia from wastewater by ion exchange in the presence of organics. Studies in a packed column showed that the presence of organic compounds had little or no effect on NH4+ removal. There was however an increase in capacity after each regeneration of the bed and continued removal after breakthrough. The same results were achieved in the control experiment with no organic compounds present, hence these results are not related to the presence of an organic compound. The presence of NH4+ and various compounds did however provide micro-organisms with substrates from which to grow causing hydraulic difficulties in the column. See chapter 6.0 for these results. The final section of experimental work studied whether the presence of organic compounds changed the rate of uptake of NH4+. The results in chapter 7.0 show that there was no effect on the rate of NH4+ uptake.