|Eva Fathul Karamah||Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia|
|Linggar Anindita||Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia|
|Devita Amelia||Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia|
|Eny Kusrini||Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia|
|Setijo Bismo||Chemical Engineering Department, Faculty of Engineering, Universitas Indonesia|
Tofu industrial wastewater is usually disposed of directly without undergoing waste treatment, a process that endangers the environment. The amounts of chemical oxygen demand (COD) and total suspended solids (TSS) in the wastewater exceed the maximum levels determined by the government of Indonesia. Ozonation and adsorption are well-known methods that can effectively degrade organic and inorganic compounds in wastewater. In this research, the removal of COD and TSS from tofu industrial wastewater was examined through the use of the ozonation method, the adsorption method using natural zeolite, and both methods combined. The sample was passed into a packed-bed column containing natural zeolite and ozone used for about 60 minutes. The effectiveness of the method was evaluated by COD and TSS degradation, with varying dosages of ozone and amounts of natural zeolite (50 g, 75 g, and 100 g). The best result was achieved by using a combination of ozonation and adsorption, with 100 g of zeolite and an ozone dosage of 155.1 mg/h, which achieved 219.4 mg/L and 25 mg/L removal COD and TSS, respectively.
Adsorption; COD; Ozonation; Tofu; TSS
Tofu is a popular traditional food in Indonesia. This has led many Indonesians to run home-based tofu businesses with traditional technology, resulting in a relatively high amount of waste. There are two types of tofu waste: solid and liquid. The solid waste is usually reprocessed into animal food, while the liquid waste is disposed of directly into the environment without undergoing a waste treatment process, which can pollute the ecosystem. The amount of liquid waste from the tofu industry is quite high compared to solid waste because almost every process involved uses water; one kilogram of tofu raw material requires 45 liters of processing water, resulting in 43.5 liters of tofu wastewater. Dinas Lingkungan Hidup DKI Jakarta reported that the average amounts of chemical oxygen demand (COD) and total suspended solids (TSS) in tofu industrial wastewater are high, at 8,640 and 2,350 mg/L, respectively. These amounts exceed the maximum levels determined by the government, which is 100 mg/L for COD and 200 mg/L for TSS.
Tofu industrial wastewater can be treated using the Advanced Oxidation Processes (AOPs) technique, which combines the ozonation and adsorption methods using natural zeolite. Ozonation is a well-known method that can degrade and reduce the toxicity of organic and inorganic compounds. Ozone can easily decompose to hydroxyl radicals, which can eliminate pollutants in wastewater (Derco et al., 2015; Desmiarti et al., 2019). The addition of adsorbent to this process can also increase hydroxyl radical production, resulting in more effective and faster oxidation of organic compounds (Fujita et al., 2004; Zhang et al., 2016; Ghuge & Saroha, 2018).
Zeolites have been widely used as an adsorbent or catalyst because of their non-flammability and thermal stability (Zaitan et al., 2016; Hidayat et al., 2018). Zeolites can function as adsorbents and catalysts because they are safe to use in catalytic oxidation processes operating at high temperatures. Ikhlaq and Kasprzyk-Hordern (2017) studied the removal of volatile organic compounds (VOC) by catalytic ozonation process using g-alumina and ZSM-5 zeolite. They found that zeolites promoted the decomposition of VOCs. The presence of hydroxyl radical scavengers had no significant effect on the removal rates of VOCs and the generation of chlorides in the presence of zeolites. Ikhlaq and Kasprzyk-Hordern suggested that catalytic ozonation of organic VOCs on zeolites proceeds via a non-radical mechanism that involves reactions of molecular ozone with pollutants adsorbed on the surface of zeolites (Iklaq & Kasprzyk-Hordern, 2017).
In the present study, the effectiveness of COD and TSS removal from tofu wastewater was analyzed by the ozonation method, the adsorption method using natural zeolite, and both combined. To find the optimum conditions for these methods, ozone dosages and amounts of zeolite were varied. The parameters evaluated were COD and TSS content before and after treatment and the formation of hydroxyl radicals.
The removal of COD and TSS from tofu wastewater is influenced by ozone dosage and the amount of zeolite. A combination of the ozonation and adsorption methods using natural zeolite is very effective in removing COD and TSS compared to the single ozonation and adsorption methods. It was found that the best condition for decreasing COD and TSS levels was achieved using an ozone dosage of 155.1 mg/h and 100 g of zeolite, which resulted in COD and TSS removal of 219.4 mg/L and 25 mg/L, respectively, after 60 minutes. This indicates that combining ozone and zeolite can improve organic and inorganic compounds removal in tofu wastewater.
The authors thank Laboratorium Intensifikasi Proses Teknik Kimia Universitas Indonesia, Laboratorium Uji AKA Bogor, and Laboratorium Uji Universitas Negeri Jakarta for their help with this research. This research project was supported by the Ministry of Research, Technology and Higher Education of the Republic of Indonesia under grant number NKB-1635/UN2.R3.1/HKP.05.00/2019.
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