Wpływ elektrolizy na zawartość azotu amonowego i ortofosforanów w wodach osadowych

Dotychczas wykorzystanie procesów elektrolizy lub elektrokoagulacji rozpatrywano najczęściej pod kątem możliwości oczyszczania wody lub ścieków. W niniejszej pracy zaprezentowano możliwości zastosowania tych metod w przeróbce osadów ściekowych do oczyszczania wód osadowych. Przedstawione rezultaty umożliwiają wyciągnięcie kilku podstawowych wniosków.1. Elektroliza z wykorzystaniem elektrod żelaznych prowadzona w osadach ściekowych wpływa na zawartość azotu amonowego i ortofosforanów w odciekach uzyskiwanych podczas odwadniania.2. Efektywność elektrokoagulacji ortofosforanów jest bardzo wysoka w układzie z elektrodami stalowymi i wzrasta wraz z powierzchnią zastosowanych elektrod. 3. Wzrost powierzchni elektrod tylko nieznacznie wpływała na efek-tywność usuwania azotu amonowego z osadów.

The use of electrolysis or electrocoagulation has been usually contemplated with respect to purification of water and wastewater. This study presents the possibility of applying the methods in sludge processing to purify sludge waters. The effect of electrolysis was determined on sludge temperature and pH change and on the concentration of biogenic compounds in effluents produced during their dehydration. The sludge used in the study was obtained from the municipal wastewater treatment plants in Olsztyn and Olsztynek. They con-tained 47 and 173 mg PO4/dm3 or 150 and 580 mg N-NH4/dm3 depending on the experimental series. Electrolysis was conducted at the voltage of 36 V with iron rods. Direct current was generated by a rectifier. The area of one electrode was changed during the experiment from 5.2 to 67 cm2. The area and shape of both electrodes were identical. The duration of electrolysis was 30 minutes. The maximum effectiveness of orthophosphate removal from sludge containing 47 mg PO4/dm3 was 95%. When electrolysis was applied to purify sludge with a higher initial concentration of orthophosphates, the highest effectiveness achieved after 30 minutes was equal to 81.4%. The effectiveness of ammonium nitrogen removal ranged from 8.5 to 13.2%. Such low effectiveness may have been caused by the short time of the process or caused by the rapid growth of the sludge temperature. The removal rate of N-NH4+ depended mainly on the initial concentration and - to a minor extent - on the area of electrodes used, which implies that both temperature and pH may have contributed to the removal of the nitrogen species. Changes of pH and temperature depended mainly on the type of sludge used. The temperature achieved with the largest electrode area ranged from 31.9 to 57.0°C. The pH increased proportionally and reached maximum values of 7.6 and 7.8 after 30 minutes of electrolysis (with an area of 67.0 cm2).