Assessment Of The Hydrodynamics Process Of Anaerobic Ponds Of Dandora Wastewater Treatment Plant: Radiotracer Application
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Date
2019Author
Adwet, Omolo Wendy Mariam
Type
ThesisLanguage
enMetadata
Show full item recordAbstract
Wastewater is a serious environmental concern when released to the environment untreated.
Dandora Waste Water Treatment Plant treats about 80,000 m3(80%) of wastewater generated
within Nairobi and its environs per day before disposal into Nairobi river. Therefore, this study
has assessed the operations of Dandora Waste Water Treatment Pond for effectiveness,
specifically, the anaerobic ponds by using radiotracer technology. Radiotracers are widely used
in industries to optimize processes by investigating reactor mixing processes and
troubleshooting. In waste water treatment plants processes, radiotracers are very sensitive and
mostly applied in online diagnosis of various operations. Approximately 5000 MBq of Iodine-
131 radiotracer was injected 40 m away from the inlet of anaerobic pond and its passage
through the channel and the entire pond was monitored by seven (7) NaI detectors to determine
the Residence Time Distribution (RTD). Volumetric flow rate of the inlet channel at the time
of injection was estimated to be 0.059 m3s-1 using radiotracer methods which provided the
theoretical mean residence time (MRT) to be 3.5 days. The measured MRT was then compared
with the theoretical MRT and dead volume was estimated, from which it was found that about
93% of the geometric volume within the pond was dead. The measured RTD was modeled
using various RTD models and eventually a suitable model was identified to describe and
visualize the flow pattern of wastewater within the pond. RTD obtained using the online
detection system shows a typical bypass of 3.0 - 3.8% followed by mass flow homogenization
of 96.2 - 97 %. It was evident that the retention time of anaerobic pond of interest was less than
the theoretical retention time thus indicating a reduction in active volume of the pond due to
sludge build-up and stagnant volumes. Based on the measured MRT, percentage of dead
volume and identified flow patterns, it was concluded that the hydraulic performance of the
pond was catastrophically poor and no longer suited for the purpose it was designed for. It is
recommended that the pond be de-sludged and follow-up experiment conducted. The results of
the wastewater effluents for weekly averages for COD, BOD, TSS and TDS exceed the design
and Kenya standards limits.
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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