1. Introduction
Lye peeling, one of the most popular tomato peeling methods,
involves the use of sodium hydroxide at high concentration
(8e25 g/100 g) and temperature (60 to over 100 C), generating a
waste solution with excessively high pH (more than 13), COD, and
organic solids (Floros & Chinnan, 1990). The spent lye needs to be
neutralized by acid before being released to natural water. It cannot
be discarded on the soil because not only does it cause high pH soil
which is not conducive to crop growth, but it also prevents bacterial
growth, making it impossible to use microbial-based waste treatment
ponds. The higher the pH, the more difficult and the less
economical it is to treat lye. Moreover, lye peeling waste will clog
pores of membrane filters, resulting in fouling and high capital cost
(Pandrangi, 1998).