بررسی وضعیت تثبیت و قابلیت استفاده مجدد لجن در چهار تصفیه خانه کوچک فاضلاب شهر تهران

At the present time, there is not a main sewerage and  sewage     treatment  plant in Tehran but some small sewage treatment plants were    built in this city. The main objectives of this study were to investigate the    stabilization  condition  and  reuse of  the disposal  sludge in  some of  these    treatment  plants.           This research completed on four sewage treatment plants consisting of     Shoush, Ghytareyh, Ekbatan and Sahebghraneyh over ten months (October    1996 to July  1997). The general condition and operation of these plants    were considered and also indexes of sludge stabilization and reuse    including VS/TS ratio, pH, flotation, color, odor, coliform and fical  coliform      were  determined.           The average ratios of VS/TS in disposal sludge of sewage treatment    plants; Shoush, Ghytareyh, Ecbatan and  Sahebghraneyh were estimated    and been 69.25%, 70%, 71% and 70.25% respectively. The average of pH    values in disposal sludge of sewage treatment plants; Shoush , Ghytareyh ,    Ekbatan  and  Sahebghraneyh  were determined and they were 6.48, 6.93,    6.68, 6.65 respectively. Also the average fical coliform density in  disposal     sludge of sewage treatment plants; Shoush, Ghytareyh, Ecbatan and    Sahebghraneyh were estimated and they were  2.61´106 , 2.68´105, 7.5´105 ,    1.2´107 per gram  respectively.           The results of this research showed  that the disposal sludge from these    plants  were  raw  and destabilized. The microbial quality of the disposal    sludge  was evaluated and  results showed that maximum was in  class B of    USEPA  category. Therefor, at  the best  condition the disposal sludge may    be used for the reconditioning the poor  soil  or  forest  areas, but never be      used as a fertilizer for  the agriculture. If these types of  sludge are used as a     fertilizer, so microbial  quality of  these  must be improved up to class A of     USEPA category  with additional stabilization process.