Residual water from coffee without recirculation can cause serious impacts if
released into the environment without treatment. The electrolytic technique appears as a
promising alternative to minimize this damage. However, high effluent times in the reactor
can make the treatment unfeasible, consuming a lot of electrical energy and increasing the
wear of the electrodes. For this reason, the objective of this study was to optimize the
Hydraulic Detention Time (Time) based on the removal of turbidity, Total Solids (TS) and
Chemical Oxygen Demand (COD), monitoring the behavior of pH and electrical
conductivity. In the experiments, a glass electrolytic reactor with a volume of 1000 cm 3
was used. Batch experiments were performed following a completely randomized design in
a subscript scheme, varying the factors: plate distance (PD: 10, 20 and 30 mm) current
density (CD: 25, 50, 75 and 100 A m -2 ) and hydraulic detention time of the reactor effluent
(Time: 0, 60, 121, 183, 247, 312, 378, 446, 516 and 586 s). After using optimization
techniques, it was found that the averages of the optimal operating conditions of the

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monitored variables are in Time intervals of 376 seconds, 70 A m -2 of CD and 26 mm of
PD, reflecting the greater removal of pollutants. The values predicted by the models
generated overestimated turbidity by 59% and underestimated TS and COD by 14% and
2%, respectively. The validation in the optimized conditions, showed removal of 68.35%,
25.55% and 3.68%, for turbidity, total solids and COD, respectively. The overall electrical
consumption was 1.75 kW.h m -3 , while the operational treatment cost was US$ 0.13 m -3 .
Electricity represents the highest cost in electrolytic treatment, about 78.8% of the total
operating cost under the conditions of the studied system, which can be reduced with the
capture of photovoltaic electricity.