Performance of vertical and horizontal treatment wetlands planted with ornamental plants in Central Chile: comparative analysis of initial operation stage for effluent reuse in agriculture.

This study comparatively evaluated effluent reuse from two TWs-a horizontal subsurface flow (HF) and a vertical subsurface flow (VF)-used for rural wastewater treatment in Central Chile during the initial operation stage. The two TWs were planted with Zantedeschia aethiopica and were operated for 10 months at a pilot scale. The water quality of the influent and effluents was measured and compared with reuse regulations. The results showed similarities in the behavior of the effluents from the two TWs, presenting differences only in the chemical oxygen demand (COD) and different forms of nitrogen, suggesting the necessity of complementary treatment stages or modifications to the operation. The effluents from the HF better fulfilled the reuse standards for irrigation, as the VF faced problems associated with its size. However, a complementary disinfection system is necessary to improve pathogen removal in the effluents coming from the two TWs, especially to be reused as irrigation water for crops. Finally, this work showed the potential for applying subsurface TWs for wastewater treatment in rural areas and reusing their effluents as irrigation water, practice that can contribute to reducing the pressure on water resources in Chile, and that can be used as an example for other countries facing similar problems.

Variation of the feeding/resting period in modified vertical treatment wetlands (depth, zeolite as medium) employed for treating rural domestic wastewater in tourist areas.

This work aimed to evaluate the performance of modified vertical flow treatment wetlands (VF-TWs) in terms of depth and medium to assess the effect of the feeding/resting periods and footprint (FP). The modifications were proposed for treating domestic wastewater in rural areas with flow variations such as tourist sites. The experimental setup included six laboratory-scale VF-TWs: (a) normal (VF-N), bed depth 1.0 m, filled with sand and (b) modified (VF-M), bed depth 0.5 m, filled with sand (upper) and zeolite (bottom, saturated). The operation was divided into three phases (3 months each), varying the feeding/resting period and FP: phase I, 5 d/10 d, 2.6 m2/person-equivalent (PE); phase II, 3.5 d/3.5 d, 1.7 m2/PE; and phase III, only feeding no resting, 0.85 m2/PE. Influent and effluent grab samples were taken every 2 weeks. The results showed effective removal (above 60%) of total solids, organic matter, and pathogens for both VF-N and VF-M. Regarding nutrients, VF-M showed a phosphate removal below 60%, but no consistent removal (15-60%) of total nitrogen. Thus, the results suggest that proposed modifications can be an option to be established in tourist sites, but further work should be conducted to improve and optimize total nitrogen removal.

Reverse Osmosis Concentrate: Physicochemical Characteristics, Environmental Impact, and Technologies.

This study's aim is to generate a complete profile of reverse osmosis concentrate (ROC), including physicochemical characteristics, environmental impact, and technologies for ROC treatment, alongside element recovery with potential valorization. A systematic literature review was used to compile and analyze scientific information about ROC, and systematic identification and evaluation of the data/evidence in the articles were conducted using the methodological principles of grounded data theory. The literature analysis revealed that two actions are imperative: (1) countries should impose strict regulations to avoid the contamination of receiving water bodies and (2) desalination plants should apply circular economies. Currently, synergizing conventional and emerging technologies is the most efficient method to mitigate the environmental impact of desalination processes. However, constructed wetlands are an emerging technology that promise to be a viable multi-benefit solution, as they can provide simultaneous treatment of nutrients, metals, and trace organic contaminants at a relatively low cost, and are socially accepted; therefore, they are a sustainable solution.

Evaluation of Bed Depth Reduction, Media Change, and Partial Saturation as Combined Strategies to Modify in Vertical Treatment Wetlands.

The aim of this work was to evaluate the performance of vertical subsurface flow treatment wetlands (VSSF TWs) for treating rural domestic wastewater when strategies such as bed depth reduction and media change are used in combination with bottom saturation. Two treatment wetland systems were implemented: normal (VF-N), with a bed depth of 1.0 m, and modified (VF-M), with a bed depth of 0.5 m and a bottom layer of natural zeolite. Schoenoplectus californicus was used as experimental plant. These two treatment systems were operated at a hydraulic loading rate of 120 mm/d in two phases. Phase I did not use bottom saturation, while Phase II involved a bottom saturation of the zeolite layer of the VF-M system. The results show that bed depth reduction did not have a significant effect (p > 0.05) in terms of organic matter, solids, and ammonium removal. Conversely, it had a significant influence (p < 0.05) on phosphate as well as a negative effect on pathogen removal. This influence could be explained by initial media capacity for phosphorus removal and filtration importance in the case of pathogens. Partial saturation only had a positive influence on total nitrogen removal. The addition of a bottom layer of natural zeolite showed no positive effect on nutrient removal. The plant showed adaptation and positive development in both VF-N and VF-M. The water balance showed that water loss was not influenced by bed depth reduction. Therefore, according to the previous results, a combination of the proposal modifications to VSSF TWs can be introduced for treating rural domestic wastewater.

Analysis of Salix humboldtiana to be used as the plant species in evapotranspirative willow systems in Latin American highland climate conditions.

This study aims to evaluate the evapotranspiration (EVP) rate of the willow species Salix humboldtiana to be used as a plant species for evapotranspirative willow system (EWS) to treat domestic wastewater in highland climate conditions in Latin America. Twelve lysimeters were installed in Bogotá, Colombia (2,600 m.a.s.l.). Two parameters were evaluated to determine the effect on EVP rate as follows: (a) the plant's age at the plantation time (one year or six months), and (b) the type of water (domestic wastewater or fertilized water). The plant's age was the most important parameter influencing the EVP rate. In addition, the growth of plants was similar (p > 0.05) between individuals irrigated with domestic wastewater and fertilized water. Thus, Salix humboldtiana over one-year-old was recommended to be used in EWS because its EVP rate of 1456 mm y-1, can treat 372 mm y-1 of domestic wastewater under the highland climate conditions. Finally, one EWS planted with Salix humboldtiana to treat domestic wastewater for a Colombian family located in these climate conditions would need an area of 400 m2. This value for area, although similar to other parts of the world, is higher when considering the solar radiation in tropical or sub-tropical climate conditions.