Mixing Water Treatment Residual with Excavation Waste Soil in Brick and Artiﬁcial Aggregate Making Chihpin Huang 1 ; Jill Ruhsing Pan 2 ; and Yaorey Liu 3 Abstract: A large quantity of water treatment residual is generated each year from fresh water treatment plants in Taiwan. Landﬁll disposal of the nonhazardous sludge is impractical because of the high cost of transportation and an increasing scarcity of landﬁll sites in Taiwan. The water treatment residual was characterized; the ceramic bodies were prepared and sintered to formulate into building bricks and artiﬁcial aggregates. The sintering temperature requirement by the water treatment residual was higher than normally practiced in brick works due to the higher Al 2 O 3 and lower SiO 2 content. The excavation waste soil, practically clay, was blended with water treatment residual to improve the brick quality. Under the commonly practiced brick-making condition, up to 15% of water treatment residual could be added to produce ﬁrst grade brick speciﬁed by the National Science Council (NSC). Test results of speciﬁc gravity, water absorption, and compressive strength of the artiﬁcial aggregates conﬁrmed its applicability in constructions as various degrees of light-weight aggregates. DOI: 10.1061/(ASCE)0733-9372(2005)131:2(272) CE Database subject headings: Aggregation; Bridge construction; Sludge disposal; Waste management; Taiwan. Introduction In Taiwan, the daily production of fresh water is approximately twelve million tons, resulting in a daily production of 24,000 – 280,000 tons water treatment residual (WTR). This amount is expected to increase dramatically because of the in- creasing demand for higher-quality water by consumers and the more stringent quality standards regulated by the government. Most WTR is disposed in landﬁlls. This means of disposal is no longer practical in many modern urban municipalities because of the difﬁculty in ﬁnding landﬁll sites and the costs of operating landﬁlls. Since the government will soon ban landﬁll disposal, searching for alternatives for sludge disposal has become a prior- ity for the water industry. Thermal treatment of sludge was originally used for the pur- pose of volume reduction and stabilization of sludge. The future trend of sludge management, however, is to convert the waste into useful material (Tay and Show 1997; John 2001). A sintering process can bond materials together, resulting in sintered matrices with sufﬁcient strength and extremely low heavy metal leachabil- ity (Wang et al. 1998). Ashes of biological sludge and municipal waste incinerator have been recycled into construction materials through this technique. Many studies on reusing sludge ashes as brick materials have been reported in both lab-scale and full-scale applications (Anderson et al. 1996; Okuno 1997; Tay et al. 1997; Wiebusch and Seyfried 1997; Liaw et al. 1998; Sorensen et al. 2001). Sludge ashes have also been made into artiﬁcial coarse and ﬁne aggregates for concrete mix (Khanbilvardi and Afshari 1995; Tay et al. 1997; Liaw et al. 1998; Wainwright and Cresswell 2001), permeable blocks and pavement bricks (Nishigaki 2000); and tile (Bernd and Carl 1997). These studies were done on com- bustion ashes of sewage sludge, industrial wastewater sludge, and municipal solid waste. Although an industrial-scale experiment on brick production with dredge harbor sediments was reported (Hamer and Karius 2002), no studies on resource reuse of the WTR have been reported. Because of the similar mineralogical composition, the WTR can be a potential substitute for brick clay. Previously, our labo- ratory had explored the possibility of blending the WTR with dam sediment to make constructional bricks (Huang et al. 2001). Due to depleting resources, there has been a growing trend in convert- ing wastes into proﬁtable products. Excavation waste soil (EWS) is one of the examples. EWS is the soil excavated from the ground before construction. In Taiwan, approximately twenty mil- lion tons of EWS are generated each year, which needs to be disposed of properly. Many local brick works have been incorpo- rating EWS as brick material. In this study, we blended the WTR with the EWS to make bricks and artiﬁcial aggregates. The char- acteristics of the products were examined and evaluated accord- ing to the Chinese National Standard (CNS) speciﬁcation for vari- ous degrees of bricks and aggregates, as shown in Table 1. The result will be adopted in a large-scale study on producing market- able constructional products from the WTR. Materials and Methods Raw Materials for Sintering WTR and EWS were the raw materials for sintering. The WTR was the dried sludge cake obtained from the Chin-Tan Water 1 Professor, Institute of Environmental Engineering, National Chiao Tung Univ., 75 Po-Ai St., Hsinchu, Taiwan, 300 (corresponding author). 2 Associate Professor, Institute of Environmental Engineering, National Chiao Tung Univ., 75 Po-Ai St., Hsinchu, Taiwan, 300. 3 Graduate student, Institute of Environmental Engineering, National Chiao Tung Univ., 75 Po-Ai St., Hsinchu, Taiwan, 300. Note. Discussion open until July 1, 2005. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be ﬁled with the ASCE Managing Editor. The manuscript for this paper was submitted for review and possible publication on May 12, 2003; approved on February 13, 2004. This paper is part of the Journal of Environmental Engineering, Vol. 131, No. 2, February 1, 2005. ©ASCE, ISSN 0733-9372/2005/2-272–277/$25.00. 272 / JOURNAL OF ENVIRONMENTAL ENGINEERING © ASCE / FEBRUARY 2005 J. Environ. Eng. 2005.131:272-277. Downloaded from ascelibrary.org by National Chiao Tung University on 04/30/14. Copyright ASCE. For personal use only; all rights reserved.