Survey of microbial quality, heavy metals and management action for waste sludge produced at the East Azerbaijan municipal wastewater treatment plants in 1393
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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.