Stormwater can have environmental impacts because it causes various pollutants to be released into the environment during precipitation events. This study quantifies the flow of different metals through an ultrafiltration membrane unit during stormwater treatment and investigates the possibility of reusing treated stormwater both as non-potable and potable purposes and of metal recovery from the backwash water obtained from membrane cleaning. The stormwater used for the ultrafiltration experiments was sampled in three catchments during different rain events. The results indicate that the permeate quality complied with most of the parameters for potable water as stipulated by the Swedish Food Agency, except in respect of manganese, nitrate and ammonia concentrations from permeate from stormwater samples originating from road runoff. The backwash water from the membrane cleaning contained metals in high concentrations, e.g. average copper concentrations were 5.2 times higher in the backwash than in the feed. Recovering metals like Cu, Ni, and Zn from backwash water could be a sustainable process, as stormwater transports 0.03 %, 0.01 %, and 0.04 % of their annual production in high-extraction countries, provided operational costs and logistics are feasible.

After energy recovery from blackwater via anaerobic digestion, technologies such as struvite precipitation and ammonia stripping can be used to enhance nutrient recovery. However, the presence of suspended solids, organics and metals, can negatively impact the nutrient recovery processes. This study examined the treatment of digested blackwater, applying either a ceramic microfiltration membrane or a drum filter, operating in parallel in a source-separated wastewater plant. The digestate as well as the permeates from the membrane and drum filter were sampled regularly and evaluated. In general, the ceramic membrane proved to be more efficient in improving the quality of digested blackwater in comparison to the drum filter. The ceramic membrane reduced total suspended solids to below the detection limit, while the drum filter achieved 74 % removal. The membrane removed 74 %, 85 % and 76 % of TOC, BOD7 and COD-Cr, respectively, higher than the corresponding treatment with the drum filter, which removed 41 %, 42 % and 34 %, respectively. No significant differences in phosphate and ammonium concentrations (P-value = 0.05), before and after both treatment methods were observed. The membrane removed particulate-bound metals (As, Cd, Cr, Cu, Ni, Pb and Zn) up to 25 %, 95 %, 87 %, 95 %, 66 %, 90 % and 98 %, respectively. The drum filter achieved lower removal for particulate-bound As, Cd, Ni, Pb and Zn for 25 %, 79 %, 44 %, 56 % and 86 %, respectively. The removal of metals is critical to maintain struvite purity and prevent the struvite contamination due to co-precipitate of these metals.

A major challenge for the reuse of greywater is micropollutants. For identification and characterisation of organic pollutant levels and distribution in environmental matrices a variety of non-target screening strategies and methods(NTS) have been developed (Hollender et al., 2023). For greywater, NTS approaches were taken in only three previous studies. Eriksson et al. (2003) annotated 191 individual compounds using GC-MS in greywater from 38 people living in apartments. Gulyas et al. (2011) annotated 80 organic compounds in raw greywater using GCMS from 103 inhabitants from an eco-settlement. Gros et al. (2017) identified 31 micropollutants using UHPLC Orbitrap HRMS in greywater from small scale (>5 person) systems.In this study a qualitative NTS is performed on greywater from Helsingborg, Sweden, and Oslo, Norway. Solid phase extraction (SPE) was used as pretreatment for qualitative analysis using Ultra High Performance Liquid Chromatography with high-resolution Time-of-Flight Mass Spectrometry (UHPLC/MS/MS-QTOF). A first quantitative overview on the identified chemical profiles will be presented and discussed in the context of new sustainable techniques and strategies for greywater treatment and reuse. The results of this study will be used for design of high-sample throughput quantitative analysis of priority pollutants to monitor greywater micropollutant content. The overarching aim of this study and follow up studies is to create a shortlist of micropollutants relevant for long term monitoring in greywater treatment installations targeted for reuse of greywater. While this study is performed on relatively large systems, the resulting shortlist of micropollutants will be used to analyse micropollutant greywater quantity in small wastewater systems as well.

Blackwater from vacuum toilets contains significant amounts of nutrients that can be repurposed as fertilizer. This study aimed to evaluate an air gap membrane distillation process to concentrate nutrients in blackwater digestate. In the first experiments, various temperatures (40°C, 55°C and 70°C) and pH levels (2.5, 2.8, 3.0, 4.0 and 6.0) were tested on the feed, resulting in operating conditions of 55°C and pH 4 for the study's second experiment. Under these conditions, a 15-fold volume reduction was achieved. In this second experiment, the average permeate flux was 1.95 Lm-2h-1 during the first 18 hours, decreasing to 0.81 Lm-2h-1 after 150 hours of operation. The membrane was cleaned when the flux dropped to 0.39 Lm-2h-1. The final concentrate had an NPK elemental weight ratio of 1:3:0.3. A chemical model indicated that most ammonium and phosphorus were dissolved in the concentrate, with some phosphate compounds precipitating. The product contained essential micronutrients and low levels of harmful substances like As, Hg, Cd, and Pb, with NaCl at 0.3% of the weight. The main challenge was membrane wetting, leading to 33% of nitrogen loss and 13% of phosphorus loss. Despite the challenges the process successfully produced a nutrient-rich concentrate beneficial for agriculture.

A polymeric ultrafiltration (UF) membrane was used for stormwater treatment, with the focus on evaluating the increase in the membrane process productivity by adding pulsatile fluid flow to UF membrane treatment. Sedimentation and sieving were used as pre-treatment. The result showed that increasing the pulse frequency from 0 to 4 Hz increased productivity from -6.6 to 82 LMH. UF membrane removed suspended solids, oil and turbidity below detection limit. The UF membrane also separated total coliforms, E. coli and P. aeruginosa below detection limit. Total organic carbon (TOC) was reduced by between 70 and 91%. In addition, the UF membrane was able to reduce BOD7 and COD to below 7 mg/L in the permeate. According to the US EPA, WHO, and national regulations in Canada,  Japan, and South Korea, treated stormwater can be used for flushing toilets and streets irrigation and agricultural use.