Abstract

Anaerobic digestion (AD) of food waste (FW) has become of great interest in recent years due to the high organic removal rates and positive net energy balance. However, two key issues should be highlighted. On the one hand, AD effluent still needs to be purified in order to meet ecologically acceptable requirements for direct disposal. On the other hand, AD plants have been mainly based on mesophilic and thermophilic temperatures, which may represent an important economic barrier for extending AD to small- and medium-sized plants. Hence, the aim of this paper is to assess the AD of FW at low temperature and the post-treatment of anaerobic digestate by using microalgae cultivation at laboratory scale. This study explores an economical alternative for small- and medium-size treatment plants loaded with FW. Inoculum and FW were physical and chemically characterized, and 5-L glass batch reactors in triplicate were used for determining the biochemical methane potential. The chemical oxygen demand (COD), biogas production and its composition were measured until the end of batch tests. The post-digestate was assessed as cultivation media for the microalgae Scenedesmus sp. by varying the dilution rate with fresh water. After 15 days, microalgae was harvested and the liquid fraction was assessed in accordance with the Chilean legal requirements. Although AD of FW at psychrophilic temperature leads to a lower biogas yield, the COD was reduced up to 97.5%, microalgae was successfully cultivated in all post-digestate dilutions, and some of them allowed the use of effluent for irrigation.

Graphic abstract

中文翻译：

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评估嗜冷条件下食物垃圾的厌氧消化和微藻培养的废水后处理

摘要

近年来，由于高有机物去除率和正净能量平衡，食物垃圾（FW）的厌氧消化（AD）引起了人们的极大兴趣。但是，应该强调两个关键问题。一方面，AD废水仍需要纯化，以满足直接处置在生态学上可接受的要求。另一方面，AD植物主要基于中温和嗜热温度，这可能是将AD推广到中小型植物的重要经济障碍。因此，本文的目的是通过实验室规模的微藻培养评估低温下AD的AD和厌氧消化液的后处理。这项研究探索了装载FW的中小型处理厂的经济替代方案。对接种物和FW进行了物理和化学表征，并使用一式三份的5升玻璃间歇反应器确定了生化甲烷的潜力。测量化学需氧量（COD），沼气产量及其组成，直到分批测试结束为止。消化后被评估为微藻的培养基Scenedesmus sp 。通过改变淡水的稀释率。15天后，收获微藻，并根据智利法律要求评估液体部分。尽管在亲热温度下FW的AD导致沼气产量降低，但COD降低了97.5％，在所有消化后稀释液中都成功地培养了微藻，其中一些允许废水用于灌溉。

图形摘要