# A Cyclic Graywater Treatment Model for Sustainable Wastewater Management Applied in a Small Scale
## 1 Introduction
[15] investigated the application of a non-aerated hybrid constructed wetland, integrating both horizontal and vertical flow configurations for graywater treatment. The study demonstrated the system's efficacy in removing heavy metals and microorganisms, achieving significant reductions in contaminant concentrations, thereby presenting it as a promising and sustainable treatment option. Ref. [16] investigated four graywater treatment methods: Type A (geotextile-fitted trickling filter and sand filter), Type B (fibrous mineral wool packs), Type C (fine-meshed plastic filter), and Type D (conventional sand filter), each with varying removal efficiencies for contaminants. Ref. [16] concluded that, while these systems effectively reduce certain pollutants, they may encounter difficulties in effectively eliminating pathogens, necessitating the incorporation of additional treatment steps for a more comprehensive and reliable graywater treatment process. Refs. [17; 18] presented a comprehensive overview of both existing and emerging graywater treatment technologies, emphasizing that current systems encounter considerable challenges in terms of efficiency, scalability, and resource recovery. Considering the complex processes of wastewater management, this study introduces a novel graywater treatment approach, namely \"cyclic treatment\", which draws inspiration from conventional wastewater treatment systems, such as macrophtye-planted filters. The process involves subjecting raw graywater to multiple treatment stages, each consisting of sand-filled containers with a gravel layer. The effluent from each stage represents progressively treated graywater, with a gradual reduction in contaminant levels. The use of a cyclic treatment system, rather than conventional continuous flow systems, is justified by its ability to better manage variable contaminant loads. The intermittent flow allows for enhanced pollutant contact time, improving the removal efficiency of contaminants in graywater. This approach provides more effective treatment by adapting to fluctuations in influent quality and preventing issues such as clogging, which can be common in continuous flow systems. The experimental setup is divided into two distinct conditions: one with the presence of quinoa plants, such as _Chenopodium Quinoa Willd_, and one without, facilitating a comparative evaluation of the role of plant-based filtration in enhancing treatment efficiency and overall performance. Notably, this study incorporates _Chenopodium quinoa_ as a filtering medium due to its unique properties that enhance filtration performance, promote natural bio-adsorption, and provide a sustainable, eco-friendly alternative to conventional materials in graywater treatment. Numerous studies have demonstrated the plant's high agronomic adaptability to adverse climatic conditions, such as elevated soil salinity, extreme temperatures, and drought, all of which are exacerbated by climate change [19; 20]. Furthermore, quinoa has been shown to tolerate salinity levels exceeding those of seawater [21], which enhances its resilience to various abiotic stresses [22]. In a greenhouse experiment, [PERSON]. [23] compared the salinity tolerance of _Chenopodium quinoa_ with that of the model halophyte _Thellungiella halophila_, finding that quinoa exhibited superior tolerance to salt stress under the tested conditions. In addition to its resilience to salinity, quinoa's phytoremediation potential makes it particularly suitable for graywater treatment. Studies have demonstrated quinoa's ability to accumulate heavy metals, such as cadmium (Cd) and lead (Pb), when exposed to varying concentrations of these contaminants [24]. As soil concentrations of Cd and Pb increased, so did their accumulation in quinoa tissues, while the dry weight of stems, roots, and seeds decreased under elevated metal levels. Similarly, [PERSON]. [25] reported that quinoa can accumulate Cd in both its root and aerial tissues, with the accumulation increasing proportionally to soil Cd concentrations.