Koottatep, Thammarat

Li, Zifu

Vinnerås, Björn

Zheng, Lei

English

Epsilon Open Archive

Editorial: Decentralizedwastewater treatmenttechnologiesZifu Li1, Lei Zheng1, Thammarat Koottatep2 and Björn Vinnerås3*1School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing,China, 2Department of Energy, Environment and Climate Change, Asian Institute of Technology, Bangkok,Thailand, 3Department of Energy and Technology, Swedish University of Agricultural Sciences, Uppsala,SwedenKEYWORDSdecentralized treatment methods, developing countries, household wastewater, fecalsludge, sewage sludge, urine and feces, village based sewer system, wastewater ofrefugee campEditorial on the Research TopicEditorial—Decentralized wastewater treatment technologiesThis Research Topic focuses on decentralized technologies as an alternative andcomplement to conventional centralized wastewater treatment processes. Decentralizedwastewater treatment solutions are being considered as an option to becoming a standardunder certain conditions as their systems have broader practical applications.Decentralized wastewater management is a significant area of focus for many researchersand a highly topical global issue. Decentralized treatment systems face different challengesthan centralized processes, and in recent years, several new technologies have beendeveloped worldwide that demonstrate more effective and reliable processes for waterand nutrient recycling, and for the safe end-use of treated sewage sludge and water fractions.The research on decentralized wastewater treatment systems can cover all the fractions oronly focus on one of them, and, in order to be implemented, the different treatmentalternatives need to be combined with each other so as to enable treatment of all thewastewater flows generated in a household. Many of the decentralized wastewater treatmentsystems rely on source separation, i.e., treating each individual wastewater stream accordingto its composition. Source separation has great potential for more effective resource recoveryas it can treat the different fractions according to their composition. In this Research Topic,we received seven contributions that look at different aspects of decentralized wastewatertreatment methods.One contribution (Engstler et al.) focused on mixed wastewater and evaluated theperformance of small-scale wastewater treatment plants in Austria. The authors evaluatedthe treatment performance of approximately 2,500 small wastewater treatment plants with acapacity of ≤50 PE (population equivalent) using external monitoring data from 2009 to2018. The main technologies represented were Sequencing Batch Reactor plants,conventional activated sludge plants, and vertical flow wetlands. The evaluation showedthat all technologies met the regulatory requirements for BOD5, COD, and NH4-N effluentconcentrations. There was no evidence of significant degradation in treatment performancewith age for any of the technologies, but many of the plants showed increased variability inOPEN ACCESSEDITED AND REVIEWED BYHuiyu Dong,Chinese Academy of Sciences, China*CORRESPONDENCEBjörn Vinnerås,Bjorn.Vinneras@slu.seRECEIVED 03 April 2023ACCEPTED 06 April 2023PUBLISHED 03 May 2023CITATIONLi Z, Zheng L, Koottatep T and Vinnerås B(2023), Editorial: Decentralizedwastewater treatment technologies.Front. Environ. Sci. 11:1199552.doi: 10.3389/fenvs.2023.1199552COPYRIGHT© 2023 Li, Zheng, Koottatep andVinnerås. This is an open-access articledistributed under the terms of theCreative Commons Attribution License(CC BY). The use, distribution orreproduction in other forums ispermitted, provided the original author(s)and the copyright owner(s) are creditedand that the original publication in thisjournal is cited, in accordance withaccepted academic practice. No use,distribution or reproduction is permittedwhich does not comply with these terms.Frontiers in Environmental Science frontiersin.org01TYPE EditorialPUBLISHED 03 May 2023DOI 10.3389/fenvs.2023.1199552performance with increasing time in operation. The vertical flowwetlands proved to have significantly more stable performance overtime compared to the other treatment systems.Several studies focused on the treatment of one of the fractions.One of the studies (Aicher et al.) focused on treatment by verticalgreen systems for graywater treatment. The researchers conducted afield study with four modules using synthetic graywater fed hourlyfor 18 weeks and monitored the performance in terms of COD, totalP, ortho-P, total N, NH4-N, andNO3-N removal. Themodules usingagricultural residues for treatment are promising, with up to 92%COD reduction together with a high reduction of N and P. Themodules using wooden chips had a lower reduction, reaching only67% COD removal and a lower reduction of N and P compared tothe agricultural residue filter.Two studies (Randall et al.; Simha et al.) focused on source-separated human urine and the effect of alkaline stabilization, theimpact of selected alkalizing chemicals, and how drying conditionsaffect the pH of the solution. (Randall et al.) presented the chemicalkinetics of CO2 entering the alkalized urine from the evaporation airduring dehydration. The rate constant increased with temperature,and the effect of pH on the chemical urea hydrolysis rate in alkalizedurine was negligible (>11). Their computer simulations showed thatCO2 dissolution was the main cause of the pH decrease, but CaCO3precipitation and NH3 volatilization fostered the pH decrease.Residual, undissolved Ca(OH)2 was shown to significantly delaythe pH decrease. Overall, this work provided valuable insights intothe CO2-induced pH decreases and into the mechanisms of ureahydrolysis in alkaline urine dehydration. The second contribution(Simha et al.) used alkaline earth hydroxides to prevent ureaseactivity in source-separated urine. The authors investigated andsimulated the solubility of Mg(OH)2 and the factors affecting itsdissolution in different types of urine, both real and synthetic. Theyfound that it took 6–16 min for Mg(OH)2 to dissolve. When freshurine was supersaturated with Mg(OH)2 (650 mgL-1), thepH increased to >10.5. The high pH inhibited the enzymaticdegradation of urea for >14 days. When 95% of the water wasremoved, the solubility of Mg(OH)2 increased to 16,240 mg L-1 andthe pH dropped below 10.In another contribution (Wang et al.), a review was conductedon technologies for the recovery of nutrients from blackwater.Nutrient recovery and recycling are of great importance insustainable development. Blackwater (BW) refers to toiletwastewater containing feces, urine, water, and toilet paper fromflushing toilets. The highly concentrated nutrients of BW could becollected through source separation and treated appropriately forefficient and economic recovery. This review provided an overviewof the characteristics of BW and different techniques for recoveringnutrients and other valuable substances. A number of thesetechnologies are currently being developed or tested at thelaboratory or pilot level. The outlook for BW nutrient recoverytechnologies is very positive due to their great potential for resourcerecovery. There is still a long way to go to develop commercialtechnologies and valuable products for the application of resource-based sanitation infrastructure and systems.Another study (Häfner et al.) used field experiments to evaluate thefertilizer potential and nitrogen value of three novel and safe recyclingproducts. The researchers fertilized white cabbage grown in three soiltypes (sand, loam, or silt) with two nitrified urine fertilizers and a fecalcompost, applied alone or in combination. The control was fertilized withorganic fertilizer vinasse. In addition to growth, the uptake ofpharmaceuticals was assessed for treatments with compost application.The two nitrified urine fertilizers had a similar fertilizing effect as vinasse,producing up to 72 t ha-1 of white cabbage. Plant uptake ofpharmaceuticals (carbamazepine) was higher in sand than in loam,with lower concentrations in the edible part compared to the outerleaves. The researchers found that nitrified urine fertilizer was apromising alternative in horticultural food production.The final paper to conclude this Research Topic looked into“Emerging dynamics and prospects in France”. The authors(Joveniaux et al.) presented a study investigating sourceseparation sanitation as an alternative to conventional sanitationmanagement. They looked at environmental conditions andagricultural use. In France, source separation systems werepreviously found mainly in single households in rural areas.However, since the 2010s, source separation has been introducedon a larger scale in urban areas. The researchers performed a cross-sectional analysis of experimental projects in three cities (Paris,Bordeaux, and Grenoble). Their analysis showed that sourceseparation is still in an emerging phase in France and iscurrently being experimented with through diversified projectsand approaches, both in terms of socio-technical choices andforms of territorial embeddedness. The authors pointed out that,beyond technical issues and shared social values, stakeholderalignment issues and organizational challenges are essential. Theyalso considered possible directions for future development, rangingfrom the spread of a homogeneous solution to the continuation of adiversity of approaches in different territories.To summarize this Research Topic, it can be seen that thecontributions covered several aspects of decentralized wastewatertreatment systems and that most of them focused on systems withseparate treatment of different wastewater fractions with a view toresource recovery and the challenges with the different treatmentalternatives that are available when decentralizing sanitation.Author contributionsBV wrote the editorial together with ZL with inputs from otherauthors.Conflict of interestThe authors declare that the research was conducted in theabsence of any commercial or financial relationships that could beconstrued as a potential conflict of interest.Publisher’s noteAll claims expressed in this article are solely those of the authorsand do not necessarily represent those of their affiliatedorganizations, or those of the publisher, the editors and thereviewers. Any product that may be evaluated in this article, orclaim that may be made by its manufacturer, is not guaranteed orendorsed by the publisher.Frontiers in Environmental Science frontiersin.org02Li et al. 10.3389/fenvs.2023.1199552

Editorial: Decentralized wastewater treatment technologies

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Editorial: Decentralized wastewater treatment technologies

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