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The ''Agios Philippos'' mine in the Kirki region (NE Greece) has been abandoned in 1998 after half a century of ore exploration without a reclamation or remediation plan. This article aims at elucidating the potential environmental risks associated with this site by quantifying pollution in tailing basins, stream waters, stream sediments and agricultural fields. Concentrations of heavy metals in the abandoned mine tailings reached 12,567 mg/kg for Pb, 22,292 mg/kg for Zn, 174 mg/kg for Cd and 241 mg/kg for As. The geoaccumulation index and enrichment factor for these metals were indicative of extremely high contamination (I geo [ 5) and extremely high enrichment (EF [ 40), respectively. Stream waters in the proximity of the mine had an acidic pH equal to 5.96 and a high sulfate content (SO 4 -2 = 545.5 mg/L), whereas concentrations of Mn, Zn and Cd reached 2,399 lg/L, 7,681 lg/L and 11.2 lg/L. High I geo and EF values for Cd, Zn and As in stream sediments indicates that surface water pollution has a historic background, which is typically associated with acid mine drainage. Agricultural fields in the proximity of the mine exhibited high I geo and EF values, which were in decreasing order Cd [ Pb [ Zn [ As. These findings urge for an immediate remediation action of the afflicted area.

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Artificial dosage of nitrate in sewer networks is considered as one of the most effective methods for odor and corrosion control. However, there is limited knowledge on the effect of temperature on the transformations that takes place during anoxic conditions. Thus, two groups of batch experiments were conducted to gain insight in the involved processes in bulk phase of a septic municipal wastewater. It can be concluded that sewer denitrification, in bulk phase, can be simplified in three stages. According to the experimental results, nitrate or nitrite is utilized for autotrophic denitrification with sulfide, while heterotrophic utilization is initiated after the completion of anoxic sulfide oxidation. Moreover, temperature is proved to have a significant impact on sewer denitrification kinetic profile, as it determines the extent of temporal nitrite accumulation. The temperature coefficient of each anoxic process, including sulfide oxidation, nitrate utilization and denitrification/nitrite utilization is experimentally calculated and temperature dependent equations are developed, providing the rate of all anoxic processes in bulk phase of sewer wastewater, in any given temperature.

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This paper presents a biological method for controlling odor problems caused by H 2 S originating from sewer networks under anaerobic conditions. The proposed method is based on the continuous addition of nitrate which oxidizes dissolved sulphide according to an autotrophic biological procedure and inhibits further sulphide production by sulphate reducing bacteria, until complete denitrification.The proposed method was first tested at laboratory in a 3 l anaerobic batch reactor simulating municipal wastewater of the city of Corfu in respect to sulphate concentration. Addition of nitrate in non-septic (not sulphide containing) wastewater inhibits the production of sulphide until complete denitrification. Heterotrophic denitrification rate was found 4.5 and 3.9 mg NO 3 -N l -1 h -1 at 25 0 C and 30 0 C respectively. Higher C/N ratio is, probably, responsible for the increased denitrification rate of the lower temperature.Interestingly, addition of nitrate in a septic wastewater led to a preferential autotrophic denitrification with sulphide as electron donor at a rate of 0.8 and 1.5 mg NO 3 -N l -1 h -1 at 25 and 30 0 C. After complete sulphide oxidation, heterotrophic denitrification takes place inhibiting any further sulfate reducing activity.The effectiveness of the method was validated by field experiments in a 6.7 Km combined sewer network in the city of Corfu, with an average wastewater flow of 500 m 3 h -1 , an average retention time of 2 h and sulphide concentrations varying from 3 to 27 mg S 2-l -1 . Continuous addition of 6.9, 15 and 27.7 Kg NH 4 NO 3 h -1 for a period of 4 to 8 hours led to an average sulphide removal efficiency of 84%, 98% and 99%, respectively.Based on these experimental results, a continuous addition of 10 Kg NH 4 NO 3 h -1 is proposed for practical implementation as the optimal dosing, considering sufficient odor control and tolerable increase of the ammonia load. The proposed method is not only effective but also financially interesting taking into account the facility cost and the monthly operational cost, during the summer months of the year.