Waste Paper Sludge Ash (WPSA) as Binder in Solidifying Water Treatment Plant Sludge (WTPS)

Abstract

Water treatment plant sludge (WTPS) is pathogen and heavy metals that can harm human health and the environment. As strict regulation had been implemented, WTPS is advised and must be treated before the waste is transported to landfill. Therefore, this research is conducted to solidify WTPS with an alternative waste material. The waste material so called as waste paper sludge ash (WPSA) was chosen as binder to be used to solidify WTPS. WPSA is a waste that is produced in bulk at the recycled paper factories. Somehow, its potentiality, especially as cement replacement materials is unknown. The objective of this research is to investigate the possibility of using WPSA as an alternative replacement material of cement in solidifying the WTPS. WPSA was used in proportions of 10, 20, 30, and 40 % as cement replacement by volume along with WTPS in fixed quantity. An additional mix without WPSA solidifying WTPS is also prepared. The effectiveness of WPSA in solidifying WTPS was determined based on the compressive strength achieved on 1, 3, 7, and 28 days of curing. High replacement amount of WPSA with at least 0.34 N/mm2 compressive strength will be selected as the best mix. Based on results obtained, the compressive strength of solidified WTPS increased with increasing curing days for all mix types. The smallest particle size and highest surface area of WPSA had contributed to the condition. Although, the compressive strength of solidified WTPS decreases with increasing WPSA percentage replacement. In addition, WPSA used in this research was a non-pozzolanic material with very porous surface area and irregular shape. In conclusion, a mix of 40 % WPSA labeled as W5 is a more sustainable mix binder in solidifying WTPS. Although, W2 with 10 % of WPSA substitution had passed the landfill acceptable limit at 0.34 N/mm2.