Abstract:

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds widely distributed in the  environment.  In  the  present  work, concentrations  of  these  organic  compounds  in  sludge samples  from  Cluj-Napoca  wastewater  treatment  plant  are  reported.  The  objective  was  to investigate PAHs in sludge from wastewater treatment plant and to assess their potential for land application. Primary sludge, fermented sludge, fermented concentrated sludge, anaerobic-digested dehydrated  sludge  and  rejection  water  samples  were  collected  monthly  from  December  2012. Ultrasonic assisted extraction with hexane was used, being followed by filtration and concentration to  dryness  in  a  rotary  evaporator;  the  obtained  residue  was  redisolved  in  acetonitrile.  High performance  liquid  chromatographic  analysis  was  achieved  using  an  Agilent  1100  system consisting in a solvent degasser, a quaternary pumping system, an autosampler, a column oven, a diode-array  detector  and  a  fluorescence  detector.  Separations  were  accomplished  using  an Envirosep  PP  column  with  acetonitrile:water  as  mobile  phase  (45:55  v/v).  Detection  limit  was 0.001 ï­g/  kg,  with  good  linearities  for all  PAHs,  with  correlation  coefficients  higher  than  0.998. PAHs with four rings appeared to be the primary components in most of the tested sludge samples, the  highest  concentration  levels  being  in  anaerobic-digested  dehydrated  sludge  samples.  The obtained results can be helpful for the regional policy makers to make proper decisions on treating the  increasing  amount  of  sewage  sludge,  to  provide  practical  reference  for  establishing  threshold values  of  PAHs  for  land  application  of  sludge,  knowing  that  the  practice  of  recycling  sewage sludge onto agricultural lands poses an additional risk of soil contamination with PAHs.

Keywords: