An energy‐efficient two‐stage passively aerated trickling filter for high‐strength wastewater treatment and reuse

Abstract

This work aimed to assess the technical and energetic feasibility of a passively aerated laboratory‐scale trickling filter, configured as a two‐stage system, to produce urban wastewater (UWW) reusable in agriculture. The trickling filter was fed continuously with high‐strength UWW at four hydraulic retention times (HRTs), that is, 10, 5, 2 and 1 day, corresponding to organic loading rates (OLRs) of 0.1, 0.2, 0.5 and 0.9 kg COD/m3/d, respectively. The results revealed a good performance in organic load removal and nitrification at the four HRTs. The trickling filter showed high organic pollutant removal efficiencies of up to 93%, 94% and 98% for chemical oxygen demand (COD), BOD5 and total suspended solid (TSS), respectively, as well as high ammonia nitrogen removal above 96% at the shortest HRT of 1 day. All physicochemical parameters were significantly lower than the allowable limits set out in ISO 16075 for category C (non‐food crop irrigation) irrigation water. The reuse of treated UWW in irrigation led to germination indexes and growth parameters of triticale (Triticosecale Wittm.) almost equal to those obtained using tap water. Energy use was found to be about 0.2754 kWh/m3 of treated wastewater, making it competitive with trickling filter plants reported in the literature. The simplicity and energy efficiency of the developed trickling filter system, combined with its capacity for almost full nitrification, make it appealing for sewage treatment in small communities in developing countries.

Editorial

“…WEJ is a journal that is ‘focused at the interface between academia and industry’, where we aim to not only disseminate the highest quality research but also help accelerate its implementation, enhancing the practice of water management. In this issue, Arous et al (2022) demonstrate the potential application of a novel trickling filter designed to treat high strength wastewaters to sufficient quality as to enable their reuse in irrigation, and to do so with a minimum input of energy. This system and others like it show great promise for enabling safe reuse of domestic wastewater in agricultural applications, and this is especially important in rural areas of developing countries that may lack both safely managed sanitation services and reliably clean and abundant water.…”