Brine wastewater with a high ammonia content from an iodine processing plant (commonly called kansui in Japan) was treated by electrolysis. The system, which can be considered as an indirect electrolytic treatment process, generates chlorine at the anodes and initiates the formation of mixed oxidants like hypochlorous acid. The oxidants then act as agents for ammonia destruction. Laboratory-scale experiments showed that high ammonia concentrations (as much as 200 mg dm −3 ) could be completely removed within a few minutes, and could be considered a good alternative for efficient ammonia removal from saline wastewaters. From laboratory-scale experiments in the batch and continuous modes, the charge dose was analyzed and used as the operating and scale-up factor. The value of the charge dose was not severely affected by changes in operating conditions such as electrode spacing and temperature. The charge dose from batch and continuous runs was found to be in the range of 23 C (mg NH 4 -N removed) −1 to 29 C (mg NH 4 -N removed) −1 . Using the charge dose obtained from laboratory-scale continuous electrolysis experiments as the scale-up factor, a pilot-scale reactor was designed, and the operating conditions were calculated. In the pilot-scale reactor tests at different flow rates, the effluent ammonia concentrations were reasonably close to the calculated values predicted from the charge dose equation.

ABSTRACT:The gelation of aqueous solutions containing syndiotacticity rich poly(vinyl alcohol) (s-PVA) and Congo red was studied. The gelation occurred even at 40°C, different from aqueous solutions containing atactic PVA (a-PVA) and Congo red. The melting point of gels, which were prepared from the solutions of s-PVA concentration of 2.5% and Congo red concentration of 0.1%, was around 90°C. The size of the junction points in s-PVA/Congo red hydrogels is larger than that of a-PVA/Congo red hydrogels at each fixed Congo red concentration. Syndiotactic sequence length plays an important role in gelation. The melting points and shear moduli of the gels prepared from dilute polymer solution at 0 -40°C changed through a maximum at around 0.1-0.3% of Congo red concentration and also a maximum at around 1.5%, identical to results reported already for a-PVA/Congo red hydrogel prepared at 20°C.