Zero-discharge solution for blackwater treatment at remote tourist facilities

This study presents a novel decentralized sanitary separation system as a zero-discharge solution for blackwater (BW) (faeces, urine and toilet paper) treatment for remote tourist facilities located in sensitive areas. The system operates with low water and energy consumption, enables safe operation and requires low maintenance. The BW was collected from two vacuum toilets (VTs) (0.8 L flush water) and separated in peat filters (PFs) to obtain a liquid fraction (LF) and a solid fraction (SF) of the BW. The LF from the PFs was thereafter treated in a biofilter (BF) and finally evaporated in the evaporation module (EM) powered by solar vacuum collectors (SVC). In the PFs, particles larger than 1 mm were reduced from the BW by 96.5%. Furthermore, the total suspended solids (TSS) mass removal efficiency of the PFs averaged 51.5%. Reduction of ammonia through nitrification was noticeably enhanced after 100 days of the system operation (max. 55.8%). 21.2% or 0.54 kg of total phosphorus (TP) was retained in the PFs, to be further composted and reused for agricultural purposes. An additional 5% or 0.10 kg of TP was retained in the BF. The final step of the LF treatment was in the EM at a sanitizing temperature of >60 °C to prevent the release of human pathogens into environment. With a total electricity consumption of 9.1 kWh/day and a heat consumption of approximately 5.1 kWh/day gained by the SVC, the system successfully integrated different approaches to treating the BW, recycling nutrients, and removing pathogens.