Wastewater Treatment of Chocolate Manufacture Industry through an Integrated Process of Electrocoagulation and Filtration

Introduction

The wastewater in the chocolate manufacture industry can be characterized as non-toxic as it contains no hazardous ingredients, but if you have a high content of total solids (TS), biochemical oxygen demand (BOD) and chemical oxygen demand (COD). The manufacturing process of making chocolate consumes industry water in several steps harvesting, cleaning, fermentation, drying, roasting, grinding, pressing, pulverizing and mixing [1]. So the proper treatment of industrial wastewater must be a sustainable process.

Electrochemical techniques are important for the treatment of industrial wastewater because they present high efficiency, easy operation and environmental compatibility; this process involves in situgeneration of coagulants by electrolytic oxidation of a sacrificial anode (aluminum) by applying a direct current. The most widely used electrode materials in electrocoagulation process are aluminum and iron. The hydrolyzed aluminum ions can form long chains of Al-O-Al-OH which may chemically adsorb a large amount of contaminating [2].

For most applications a proper disinfection of the water reused, is required. For disinfection of the effluent turbidity and suspended solids must be reduced to prevent the hiding of pathogens and organisms hide behind these solids. Currently, the most widely used process to remove residual SST is treated effluent filtration [3].

Materials and methods

Sampling

The wastewater samples were collected at the effluent of an industrial chocolate manufacture. The electrocoagulation and filtration were monitored for color, turbidity, pH and chemical oxygen demand A UV-Vis spectrum of the effluent was done.

Electrocoagulation process

The electrocoagulation was carried using two rectangular commercial aluminum plates served as anode and cathode. The anodic and cathodic active surface area were 343 cm² immersed in wastewater with 0.1372 cm^-1 of SA/V ratio and 0.2915 mA cm⁻²current density that was kept for 120 min.

Filtration process

Horizontal conventional downflow filter was used for filtration process; gravel 1/4 "X 1/8", gravel 1/8 "X 1/16" and 0.71 mm effective size sand as filter material. First filtration process was carried out after having completed the electrocoagulacion process. The second filtration process was carried out after completion of the first filtration process (Fig. 1)

Results

Table 1 presents the initial physicochemical parameters of wastewater, it presented contamination with organic and inorganic matter that is reflected in the values of COD. The color value obtained is harmful to aquatic life inhibiting the photosynthesis-based biological processes. 

After 120 min of treatment, the color reduction for electrocoagulation process was 89.4%; similar values were obtained in the turbidity removal (Fig. 2). In the electrocoagulation process, the Al³⁺ and OH⁻ions generated at the electrode surfaces react in the wastewater to form aluminum hydroxide; the amorphous and gelatinous aluminum hydroxide that displayed various shapes and sizes (flocs) destabilize and aggregate the suspended particles or precipitate and adsorb dissolved contaminants.

In electrocoagulation, first and second filtration processes, the turbidity removal was 89% */- 0.5; this value was obtained from the 30 minute for the second filtration process (Fig. 3) 

The concentration of dissolved oxygen in the treated wastewater increased after filtration processes as shown in Fig. 4. These results are good because the adequate dissolved oxygen is needed for good water quality and necessary for all forms of life element. 

The spectrum for the raw wastewater (Δ) presents a baseline with one absorbance peak at 290 nm which is associated with the contaminants in this matrix. For 120 minutes of reaction the removal of organic contaminants were indicated by the decrease in the absorption band at 290 nm and baseline (Fig. 5).

Conclusions

Removing contaminants was made more efficient by integrating electrocoagulation and filtration processes which is reflected in increase of turbidity removal percentage and decreased in the absorbance peaks of the spectrum for the wastewater treated.

References

[1] Keijbets EL, Chen J, Vieira J. Chocolate demoulding and effects of processing conditions. Journal of Food Engineering. 98:133–140. 2010.

[2] García-Morales MA, Roa-Morales G, Barrera-Díaz C, Martínez Miranda V, Balderas Hernández P, Pavón Silva TB. Integrated Advanced Oxidation Process (Ozonation) and Electrocoagulation Treatments for Dye Removal in Denim Effluents. Int. J. Electrochem. Sci. 8:8752 – 8763. 2013.

[3] Elbana M, Ramírez de Cartagena F, Puig-Bargués J. Effectiveness of sand media filters for removing turbidity and recovering dissolved oxygen from a reclaimed effluent used for micro-irrigation. Agricultural Water Management. 111: 27– 33. 2012.