Deep-sea mining has been regarded as one of the most promising technologies to meet the increasing demands for minerals and metals. The exploration of renewable energy supply solutions should be prioritized because the current solutions are highly dependent on fossil fuels. In this study, recognizing that the wastewater transported with minerals to the production support vessel is a potential cold source, the wastewater energy recovery is proposed for the first time. Focusing on exploring an efficient and cost-effective solution for wastewater energy recovery, the organic Rankine cycle (ORC) using six working fluids and Kalina cycle are investigated, and a multi-objective optimization for the levelized cost of electricity (LCOE) and exergy efficiency is presented. Based on the design criteria and measured data of the Solwara 1 Project of Nautilus Minerals, optimization results show that R601 with the highest critical temperature used in ORC performs best in terms of LCOE (0.102 $/kWh) and exergy efficiency (40.2%), compared with 0.125 $/kWh and 42.5% of ammonia-water mixer (0.966/0.034) used in Kalina cycle. In addition, the discounted payback periods of ORC and Kalina cycle are 12.71 years and 18.95 years respectively, indicating that ORC is economically more feasible than Kalina cycle. Moreover, the feasibility of the proposed system is validated by its economic benefits, good performance compared with ocean thermal energy conversion systems, and high flexibility and compatibility. The wastewater energy recovery is expected to provide a sustainable and low-carbon energy supply idea for deep-sea mining.

深海采矿被认为是满足对矿物和金属日益增长的需求的最有前途的技术之一。应优先探索可再生能源供应解决方案，因为当前的解决方案高度依赖化石燃料。在本研究中，认识到与矿物一起输送到生产支持船的废水是潜在的冷源，首次提出了废水能量回收。专注于探索一种高效且具有成本效益的废水能量回收解决方案，研究了使用六种工作流体的有机朗肯循环 (ORC) 和 Kalina 循环，以及对平准化电力成本 (LCOE) 和火用效率的多目标优化被表达。 $/kWh) 和火用效率 (40.2%)，而 在 Kalina 循环中使用的氨水混合器 (0.966/0.034)为 0.125 $/kWh 和 42.5%。此外，ORC 和 Kalina 循环的贴现回收期分别为 12.71 年和 18.95 年，表明 ORC 比 Kalina 循环在经济上更可行。此外，该系统的可行性通过其经济效益、与海洋热能转换系统相比的良好性能以及高度的灵活性和兼容性而得到验证。废水能源回收有望为深海采矿提供可持续、低碳的能源供应思路。