Green coagulants extracted by salt solution for coffee processing wastewater treatment

Wet coffee processing produces large amounts of liquid effluent, known as coffee processing wastewater (CPW). CPW is considered a pollutant due to its low pH and high concentrations of organic matter, salts, and nutrients. Because of these characteristics, it is essential to treat this effluent before discharging it into the environment. One promising option, which is still little studied or employed, is coagulation-flocculation followed by dissolved air flotation (C/DAF). Coagulation-flocculation is a simple and efficient method, while dissolved air flotation can allow the same volume of pollutants to be removed from the sediment in a shorter period of time. Conventionally, metallic salts are used in coagulation-flocculation; however, these products can be harmful to the environment and to human health. One possible option for study is replacing the metallic salts by natural coagulants, such as the seeds of Moringa oleifera sp. and cladodes of Hylocereus polyrhisus sp. (red pitaya). The aim of this research, therefore, was to evaluate C/DAF using the seeds of Moringa oleifera sp. and a cladode from Hylocereus polyrhisus sp. in a saline calcium chloride solution in the treatment of CPW, optimizing the doses of coagulants and salt using a central rotational composite design (CCRD). From the results, it was found that using Moringa oleifera sp., about 80% of turbidity were removed, and that using the H. polyrhisus sp. cladode, turbidity removal was about 63%. For the water under study the optimal values for dose and salinity using Moringa oleifera sp. are up to 1.2 g center dot L-1 and 2.5 to 4 g center dot L-1, respectively. When using Hylocereus polyrhisus sp., the optimal values for dose and salinity are between 1.1 and 5 g center dot L-1, and 2.3 and 3.5 g center dot L-1, respectively. It can be seen that dissolving natural coagulants in saline solution is an interesting alternative in the treatment of CPW, as it allows a reasonably efficient removal of contaminants without employing other products such as metallic salts or alkalizing products.

Automated summary

Wet coffee processing produces large amounts of liquid effluent, known as coffee processing wastewater (CPW). It is important to treat this effluent before discharging it into the environment because of its characteristics. One potential option is coagulation-flocculation followed by dissolved air flotation (C/DAF). This research evaluated the use of natural coagulants in a saline calcium chloride solution for the treatment of CPW and found promising results.