Researchers have paid particular attention to the disposal of sludge produced in water treatment plants (WTPs) into wastewater treatment plants (WWTPs) for further processing, mainly because it is considered an attractive alternative for the treatment of waste generated in water production processes. This study evaluated the effects of flow equalization and disposal of sludge, from a conventional WTP, into a WWTP system that includes an anaerobic stabilization pond followed by a facultative pond. During the period of sludge discharge from the WTP into the wastewater system, the influent to the WWTP presented an increase of 17% (from 171 to 200 mg L−1) of total suspended solids (TSS) and a 7.0% flow rate increase, without showing adverse effects on the organic load, TSS and nutrients removal. The most significant impact observed in the WWTP was the increase of solids accumulation rate in the anaerobic pond, with a value of 141 mm/year during the sludge discharge period. The operating time, before the dredging and desludging cycles required for this specific anaerobic pond, decreased from 12.7 to 10.4 years, which is consistent with previous studies in literature. Thus, based on the observed parameters of this study, it is viable to release solids from a WTP effluent into a WWTP that includes anaerobic stabilization ponds followed by a facultative pond. Indeed, this process scheme becomes a viable technical, environmental, and economical alternative for small to medium WWTPs.