Abstract
The coffee industry generates a significant amount of wastewater that is rich in organic loads and is highly acidic. The present study investigates the potential of the heterogeneous photocatalytic oxidation process to reduce the pollutant load in coffee processing wastewater. The experimental runs were conducted to evaluate the effect of operative parameters such as pH, catalyst dosage, intensity of UV light irradiation, and addition of oxidant on Chemical Oxygen Demand (COD) and colour reduction. Significant results for COD and colour removal, 67%, and 70% respectively, were achieved at a pH of 4 with titanium dioxide (TiO2), and a catalyst dosage of 500 mg/L, using four ultraviolet-C (UV-C) lamps of 16 W each. With the addition of hydrogen peroxide (H2O2) as an oxidant, the removal efficiency increased to 84% and 75% for COD and colour, respectively. Finally, the best results obtained by photocatalytic degradation using UV light were compared to those using solar light. Based on the investigation, it was inferred that the pollutant removal efficiency in coffee pulping wastewater was also considerably high under sunlight. These findings may have relevance in terms of application in countries where coffee processing is carried out and where sunlight irradiance is usually strong: the technique could be exploited to decrease the pollutant content of this wastewater sustainably.
Highlights
Coffee belongs to the genus Coffea of the Rubiaceae family, and the two well-known species of coffee grown are the Arabica and Robusta [1]
The physicochemical parameters such as Coffee wastewater was collected from the pulping process from a coffee processing industry colour, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), pH, turbidity, total suspended solids (TSS), total dissolved solids (TDS), suspended located in Karnataka, India
As colour, COD, BOD, pH, turbidity, total suspended solids (TSS), total dissolved solids (TDS), The samples were taken from the same huge tank at the company site; each experimental suspended solids (SS), nitrate-nitrogen and phosphate were analyzed as per the standard procedure run was completed with wastewater having the same chemical and physical properties
Summary
Coffee belongs to the genus Coffea of the Rubiaceae family, and the two well-known species of coffee grown are the Arabica and Robusta [1]. Coffee is processed by dry and wet methods in which the wet method yields superior quality coffee compared to the dry one. In the conventional wet processing method, the coffee industry uses a massive quantity of water during the various stages of the process. Wet processing of coffee involves the removal of outer parts of the fruit, including the skin, pulp, mucilage layer, and the parchment. This is an essential step in coffee production that decides the quantity of wastewater generated and of coffee pulp. In small-scale companies using mechanical pulpers, water usage for coffee processing varies from 2.25 to 23 m3 per ton of processed fruit, suggesting the potential of wastewater generation [3,4]
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