In this study, the anaerobic digestion of thermally hydrolyzed wasted sludge (THWS) with a high concentration of ammonia was carried out through combining with an ammonia stripping and an electrolyzed water system (EWS). The EWS produced acidic water (pH 23) at the anode and alkaline water (pH 1112) at the cathode with an electro-diaphragm between the electrodes that could be applied to ammonia stripping. The ammonia stripping efficiency was strongly dependent on the pH and aeration rate, and the ammonium ion removal rate followed pseudo-first-order kinetics. From the BMP test, the methane yield of THWS after ammonia stripping using the EWS was 2.8 times higher than that of the control process (raw THWS without ammonia stripping). Furthermore, both methane yield and ammonium removal efficiency were higher in this study than in previous studies. Since ammonia stripping with the EWS does not require any chemicals for pH control, no precipitated sludge is produced and anaerobic microorganisms are not inhibited by cations. Therefore, ammonia stripping using the EWS could be an effective method for digestion of wastewater with a high concentration of ammonium nitrogen.
An electrolytic process based on chlorine generation was adopted to treat wastewater containing textile dyes. In situ production of hypochlorous acid was achieved in an undivided electrolytic cell. The cell contained a graphite rod as the anode and a stainless steel sheet as the cathode. The generated chlorine reacts with water leading to the formation of hypochlorous acid and hydrochloric acid. The resultant hypochlorous acid, being an oxidising agent, oxidises the organic components present in the textile wastewater. In this study, the colour in wastewater containing Procion Navy and Procion Red dyes, respectively, was completely removed after 40 min of electrolysis at a constant current density of 39 mA/cm2 (where the initial dye concentrations were 3700 and 3200 mg/l, respectively). In the case of the Procion Yellow and composite dyes, complete colour removal occurred after 50 min of electrolysis (with initial dye concentrations of 3500 mg/l). Even though colour removal occurred during the electrolysis process, it required up to 180 min of electrolysis to reduce the COD values for the four dyes (Procion Navy, Red, Yellow and the composite) from the initial levels of 4520, 4200, 4170 and 4283 mg/l to 70, 45, 39 and 52 mg/l, respectively. This clearly indicates that the process removes both colour and organic components present in textile wastewater.
Microbe(s): Viruses, Hepatitis B Virus, HIV
Electrolyzed products of sodium chloride solution were examined for their disinfection potential against hepatitis B virus (HBV) and human immunodeficiency virus (HIV) in vitro. Electrolysis of 0.05% NaCl in tap water was carried out for 45 min at room temperature using a 3 A electric current in separate wells installed with positive and negative electrodes. The electrolyzed products were obtained from the positive well. The oxidation reduction potential (ORP), pH and free chlorine content of the product were 1053 mV, pH 2.34 and 4.20 ppm, respectively. The products modified the antigenicity of the surface protein of HBV as well as the infectivity of HIV in time- and concentration-dependent manner. Although the inactivating potential was decreased by the addition of contaminating protein, recycling of the product or continuous addition of fresh product may restore the complete disinfection against bloodborne pathogens.