Environmental sustainability of municipal wastewater treatment through struvite precipitation: Influence of operational parameters

JOURNAL OF CLEANER PRODUCTION

卷:285

Article

Mavhungu, Avhafunani¹  Foteinis, Spyros²  Mbaya, Richard¹  Masindi, Vhahangwele^3,4  Kortidis, Ioannis⁵  Mpenyana-Monyatsi, Lizzy⁶  Chatzisymeon, Efthalia² 

[1] Tshwane Univ Technol, Dept Chem Met & Mat Engn, Staatsartillirie Rd, ZA-0183 Pretoria, South Africa

[2] Univ Edinburgh, Inst Infrastruct & Environm, Sch Engn, Edinburgh EH9 3JL, Midlothian, Scotland

[3] Council Sci & Ind Res CSIR, Built Environm BE, Hydraul Infrastruct Engn HIE, POB 395, ZA-0001 Pretoria, South Africa

[4] Univ South Africa UNISA, Sch Agr & Environm Sci, Dept Environm Sci, POB 392, ZA-1710 Florida, South Africa

[5] Univ Zululand, Dept Phys & Engn, ZA-3886 Kwa Dlangezwa, South Africa

[6] Tshwane Univ Technol, Fac Sci, Dept Environm Water & Earth Sci, Private Bag X680, ZA-0001 Pretoria, South Africa

关键词: Wastewater valorisation;    Waste beneficiation;    Low- and middle-income countries (LMIC);    Magnesium ammonium phosphate (struvite NH4MgPO4 center dot 6H2O);    SimaPro;    Net impact or net environmental benefit (NEB) approach;   

DOI  :  10.1016/j.jclepro.2020.124856

来源: Elsevier

【 摘 要 】

The environmental sustainability of wastewater treatment through phosphate (P) and ammonia (N) chemical precipitation (struvite) was examined using the life cycle assessment methodology. Thermally activated (calcined) cryptocrystalline magnesite was used towards struvite formation and four process parameters (contact time, magnesite dosage, initial wastewater pH and temperature) were studied. Raising wastewater's temperature to promote ammonia stripping was found to be environmentally unsound. Magnesite dosage and contact time were identified as environmental hotspots, but not pH. In terms of environmental relevance, when using ReCiPe 2016 life cycle impact assessment method, the human health damage category was mostly affected, followed by resource availability, while ecosystems category was affected to a much lesser extent. Environmental impacts were grossly attributed to South Africa's fossil fuel-dependent energy mix, suggesting that renewable energy could largely improve the system's environmental performance. The optimal conditions, from the environmental perspective, were found to be 0.2 g L-1 feed dosage and 10 min mixing, at ambient temperature and pH (total environmental footprint 60.9 mPt per treated L of wastewater). To improve N removal efficacy, which is desirable in real-world applications, higher feed dosages and mixing durations are required, albeit at the expense of environmental sustainability (e.g. the 180 min and 16 g L-1 environmental footprint sharply rises to 1.87 mPt L-1). The net impact approach revealed that the avoided environmental impacts on the midpoint impact categories freshwater and marine eutrophication grossly outweigh the corresponding environmental impacts of the treatment process. Results suggest that when using a low contact time and magnesite dosage, struvite precipitation could act as a fast, efficient, and environmentally friendly pre-treatment step to practically remove P and grossly reduce N from wastewater. On the other hand, with higher feed dosages and mixing durations, struvite precipitation could act as a promising secondary wastewater treatment method with an overall low environmental footprint. Overall, results complement the existing body of knowledge on the techno-economic performance of such systems and provide insight to decisionand policy-makers to sustainably scale up the process, at village- or industrial-level, in rural South Africa, Lesotho, and further afield. (c) 2020 Elsevier Ltd. All rights reserved.

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