Dairy Wastewater Treatment with Organic Coagulants: A Comparison of Factorial Designs

Gustavo Lopes Muniz,Magno dos Santos Pereira,Alisson Carraro Borges

doi:10.3390/w13162240

Gustavo Lopes Muniz, Magno dos Santos Pereira + Show 1 more

Open Access

https://doi.org/10.3390/w13162240

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Abstract

Optimization of coagulant dosage and pH to reduce the turbidity and chemical oxygen demand (COD) of synthetic dairy wastewater (SDW) was investigated using a full factorial design (FFD) and full factorial design with center point (FFDCP). Two organic coagulants, polyacrylamide (PAM) and Tanfloc were used. The optimal values of coagulant dosage and pH were determined using a multiple response optimization tool and desirability function. The results obtained revealed that the optimum condition for removing turbidity and COD were at pH 5.0 using 50 mg L−1 of coagulant. The same optimum point was obtained in both experimental designs, indicating a good agreement between them. In optimum conditions, the expected removal of turbidity was above 98% with PAM and above 95% with Tanfloc. The estimated COD removal was above 72% with PAM and above 65% with Tanfloc. The addition of center points with replicates in the factorial design allowed to obtain the estimate of the experimental error with a smaller number of runs, allowing to save time and cost of the experimental tests. Moreover, the addition of center points did not affect the estimates of the factorial effects and it was possible to verify the effect of curvature, allowing obtaining information about the factors at intermediate levels.

Highlights

Wastewater treatment systems require coagulant dosages that provide pollutant removals at specific levels
The absence of coagulant revealed turbidity and chemical oxygen demand (COD) removal efficiencies below 40% which is not satisfactory in terms of disposal of wastewater in water bodies, as under these conditions, synthetic dairy wastewater (SDW) still has high levels of contaminants that will be harmful to the environment
The results revealed the excellent performance of PAM and Tanfloc, mainly in an acidic medium

Summary

Introduction

Wastewater treatment systems require coagulant dosages that provide pollutant removals at specific levels. The efficiency of coagulants is highly dependent on the pH value since each coagulant has a specific pH range in which it may be more or less efficient [1,2,3]. Determining the dosage of coagulant and pH at which coagulation/flocculation is most efficient is essential for a good performance of the treatment system and to minimize the costs arising from this process

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Results

Conclusion