| dc.description.abstract | Background and aim
Municipal wastewater treatment results to the production of large quantities of
sewage sludge, which requires proper and environmentally accepted management
before final disposal. Land application, landfilling, incineration and lagoon
treatments are the main techniques which are used for sludge disposal. Among
them, Land application is one of the economical and effective methods that is
broadly all around the world. However, beside its beneficiary uses, soil
amendment using sewage sludge may raise concerns about heavy metal leaching
as well as microbial contamination. Hence, qualitative evaluation of sewage
sludge before any kind of application is necessary. The present study was aimed
to investigate microbial quality, heavy metal content and management actions in
sewage sludge produced at wastewater treatment plants in Azerbaijan province.
Materials and Methods
Nine wastewater treatment plants were chosen in East Azerbaijan province, and
their sludge from drying bed was studied. Heavy metal content, total coliforms,
Fecal Coliforms, Salmonella spp., helminth ova and physico-chemical
characteristics was surveyed during winter time, 2015.
Results
Heavy metal concentration in all samples studied was in the range of standards
has set by USEPA. In case of total coliform, sludge sample from Jolfa with
1.82×106 MPN g-1 showed the highest contamination, while Sarab showed lowest
fecal coliform count with 2.02×103 MPN g-1. As in case for fecal coliform, the
bacteria count for thermo-tolerant coliforms was higher in Jolfa than other cities;
on the other hand Ahar with no fecal coliform count or less than 2.2 showed the
minimum contamination rate to fecal coliforms. In case of Salmonell spp., sludge
samples from Ahar and Bostan Abad did not show any salmonella. While sludge
sample from Tabriz wastewater treatment plant determined as the most
contaminant sludge with bacteria count equal to 83.47 per 4g. Moreover, sludgeII
sample from Sarab wastewater treatment plant showed the least contamination
rate, and bacteria count was 5.62 per 4g. Helminth ova was varied between 2.8 to
22.5 per g of sludge.
Conclusion
It can be concluded that heavy metal concentration did not exceeded the limits has
set by USEPA and european union but some heavy metal concentration exceeded
the limits has set by Iran Department Of Environment. From the stand point of
microbial quality all sludge samples met class B standards has set by USEPA,
while none of them could provide class A standards. Most of the treatment plants
have violated helminth ova standards and they need to improve sludge treatment
facilities. | en_US |
