| Author | Chalermraj Wantawin |
| Call Number | AIT Diss. no. EV-87-1 |
| Subject(s) | Nitrification
|
| Note | A dissertation submitted in the partial fulfillment of the
requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | The investigation on the mutual relationships between
heterotrophic and nitrifying activity in the same stage of continuous
process was done in order to determine the relationships aside from the
certain effects of sludge age and dissolved oxygen which usually were
referred to be the reasons for no nitrification in reactors receiving
high organic loading. More emphasis was placed on to clarify whether
the heterotrophic growth exerts the adverse effects on nitrification.
Chemostats were employed with various values of investigated hydraulic
retention time which is equal to sludge age in once through reactor.
Ammonia was fed without organic carbon in one series of experiment as
the control and ammonia was fed with different concentration of organic
carbon in other series to introduce the different degree of the growth
of terotrophsin the system.
Experimental data collected at steady state in this study
reveals that utilization of ammonia for heterotrophic cell synthesis
exhibited the preferential process over nitrification and the extent
of achievable high ammonia removal by nitrifying organism was dependent
on the growth of heterotrophs . Inhibition on the growth of ammonia
oxidizers by the presence of heterotrophs was found, more ammonia
leakage being observed under higher COD concentration in the influent.
The larger value of saturation constant for ammonia oxidation in Monod
equation, K 1 was obtained from the data of system fed with higher s'
influent COD concentration, which means the low affinity of ammonia with
ammonia oxidizers under the high activity of heterotrophs. More
inhibition on nitrification has been observed when heterotrophs grew
excessively during the transient state than that under steady state
condition. Accumulation of ammonia was found in this period and was adequately explained by the simulation of the model in which the increase
of Ks 1 value with the temporary increase of the heterotrophs was taken
s,
into account. Reduced dissolved oxygen level controlled at 0.5 mg/l
did not affect ammonia oxidation but nitrite oxidation in the control
and nitrite was accumulated up to 60 mg/l at hydraulic retention time
of 6.5 days . The degree of inhibitory effect of ammonia oxidation in
the presence of heterotrophs increased under this reduced dissolved
oxygen concentration.
Providing longer mean cell residence time and maintaining
higher dissolved oxygen are necessary for nitrifying system to achieve
the reliable stability of nitrification in the combined treatment
process, and the required mean cell residence time to maintain certain
level of effluent ammonia depends on organic carbon concentration in
the substrate . |
| Year | 1987 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering (EV) |
| Chairperson(s) | Hanaki, K. ;Vigneswaran, Saravanamuthu
|
| Examination Committee(s) | Suphat Vongvisessomjai ;Chongrak Polprasert ;Henze, M.
|
| Scholarship Donor(s) | Japan |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1987 |