Factorial Analysis on Sulfide Removal from Petrochemical Industry Wastewater using Acclimatized Activated SludgeNorazwina Zainol, Akmal Arif B. Mohamed Zaki, Nur Hidayah Mat Yasin, Sunarti Abd Rahman, Azilah Aziz and Chin Sim YeeMATEC Web Conf., 111 (2017) 02001DOI: https://doi.org/10.1051/matecconf/201711102001