**Hugo Sakamoto, Flávia M. Ronquim, Marcelo Martins Seckler and Luiz Kulay \***

Chemical Engineering Department, Polytechnic School of the University of São Paulo, Avenida Professor Lineu Prestes, 580, Bloco 18—Conjunto das Químicas, São Paulo 05508-000 SP, Brazil; hugo.sakamoto@usp.br (H.S.); flavia.mronquim@yahoo.com.br or flaviamr@usp.br (F.M.R.); marcelo.seckler@usp.br (M.M.S.) **\*** Correspondence: luiz.kulay@usp.br; Tel.: +55-11-3091-2233

Received: 12 December 2018; Accepted: 14 January 2019; Published: 21 January 2019

**Abstract:** This study aims to evaluate the environmental and energy effects of the reuse of 1.0 m<sup>3</sup> of water in a cooling tower obtained from an oil refinery effluent. An arrangement comprising reverse osmosis (RO), evaporation (EV), and crystallization (CR) was created for water desalination. Six process routes were evaluated; for this purpose, each of them was converted into an specific scenario of analysis: S1: pre-treatment with Ethylenediaminetetraacetic acid (EDTA) + RO + EV (multi-effect distillation) + CR; S2: S1 with pre-treatment by BaSO4; S3: with Ca(OH)2/CaCO3/HCl; S4: S3 with waste heat to supply the thermal demand of EV; S5: S3 with steam recompression in EV; and, S6: S3 with HNO3 in place of HCl. The analysis was carried out by attributional LCA for primary energy demand (PED) and global warming (GW) impacts. The comparison was carried out for a reference flow (RF) of: add 1.0 m<sup>3</sup> of reused water to a cooling tower with quality to proper functioning of this equipment. S4 presented the best performance among the analyzed possibilities (PED: 11.9 MJ/RF; and GW: 720 gCO2,eq/RF). However, dependence on other refinery sectors makes it inadvisable as a regular treatment option. Thus, S5 appears as the lowest impact scenario in the series (PED: 17.2 MJ/RF; and GW: 1.24 kgCO2,eq/RF), given the pre-treatment technique of RO-fed effluent, and the exclusive use of steam recompression to meet total EV energy demands. Finally, an intrinsic correlation was identified between RO water recovery efficiency and the accumulated PED and GW impacts on the arrangements that operate with heat and electricity.

**Keywords:** water recycling; wastewater treatment; environmental and energy performance; life cycle assessment (LCA); crude oil refining
