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Fortification of soil-based wastewater treatment systems with versatile ubiquitous reactive media for enhanced removal of phosphorus and other pollutants
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. KTH Royal Institute of Technology. (Land and Water Resources Engineering)ORCID iD: 0000-0002-5702-2820
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Concerns about potential risks posed by discharge from small-scale wastewater treatment (SWT) systems to receiving water bodies have prompted robust enforcement of national discharge quality standards in rural areas of most developed countries. Consequently, communities in such places are in need of effective technologies with which to achieve compliance. Currently, reactive filter (RF) media are increasingly preferred over advanced alternatives, due mainly to their simplicity, affordability and proven potential. However, many of the field-tested filters are commercial products which are costly and scarce but also only capable of removing few contaminants they are engineered to target hence often requiring to be coupled with other treatment units to achieve full treatment. In the preliminary findings of this study, biochar (BC) was identified and thus suggested basing on existing literature, as a versatile ubiquitous low-cost material for treating wastewater. Its effectiveness in fortifying sand (Sa) and gas concrete (GC)-based SWT facilities was later demonstrated in long-term experiments using laboratory packed bed reactors and field constructed filter beds. The efficacy of SaBC and GCBC systems in reducing turbidity (>95%), DOC (60%; p<0.05) and PO43- (40-90%; p<0.05) was significantly higher than for their reference counterparts. Further, sorbed P was more leachable from Sa (11.2 mgkg-1) and SaBC (20.5 mgkg-1) filters but more extractable and hence plant-available in GC (65-91 mgkg-1). Therefore, the study concluded that fortification of soil-based systems with biochar filters may be a promising solution in enhancing performances of soil-based wastewater treatment systems, while P-rich RF media can act as a nutrient source for plants if recycled to agriculture.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 53 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; LWR-2017:04
Keyword [en]
Biochar, Fortified filter, Gas concrete, Phosphorus removal, Reactive filter media, Wastewater treatment
National Category
Other Environmental Engineering
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-207777ISBN: 978-91-7729-452-8 (print)OAI: oai:DiVA.org:kth-207777DiVA: diva2:1098281
Public defence
2017-06-15, Sal V1, Teknikringen 76, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

NB: Research Funder was: Botswana International University of Science and Technology, Botswana. QC 20170524

Available from: 2017-05-24 Created: 2017-05-23 Last updated: 2017-05-24Bibliographically approved
List of papers
1. Phosphorus removal from wastewater by field-scale fortified filter beds during a one-year study
Open this publication in new window or tab >>Phosphorus removal from wastewater by field-scale fortified filter beds during a one-year study
2016 (English)In: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, Vol. 37, no 23, 2953-2963 p.Article in journal (Refereed) Published
Abstract [en]

Due to low availability of alternative technologies, rural communities are unable to comply with national wastewater discharge limits. This study tested the effectiveness of filter bed fortification with biochar on phosphorus removal. Water-tight down-flow beds of sand and gas concrete, constructed alongside a reference sand bed (all 0.8 m deep and 0.75 m2 surface area), were topped with a 0.2 m biochar layer. Pre-treated domestic wastewater with mean concentrations of 6.4 mg/L PO3-4 and 142.6 NTU, was infiltrated at 4 cm/d hydraulic loading rate. Ultimately, the biochar-sand was relatively outstanding in turbidity reduction, achieving < 5 NTU. The biochargas concrete exhibited superior performance in PO3-4 removal, trapping 32.3 g (40.2%), compared with 20.5 g (25.6%) and 15.5 g (19.3%) by biochar-sand and reference bed respectively. However, statistical analysis revealed a weak correlation between pH and biochargas concrete removal efficiency (r2= 0.2). The relationship was stronger for biochar-sand PO3-4 (r2 = 0.5) than reference (r2 = 0.4) bed. Paired samples t-tests showed that incorporating biochar into the sand bed significantly (p =.04) improved its PO3-4 removal efficiency. In conclusion, sand bed fortification with biochar could be an important measure for improving P removal and wastewater clarification efficiency.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keyword
Biochar, fortified filter beds, gas concrete, phosphorus removal, wastewater treatment
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-196064 (URN)10.1080/09593330.2016.1170888 (DOI)000384650700001 ()27043354 (PubMedID)2-s2.0-84988318621 (Scopus ID)
Note

QC 20161117

Available from: 2016-11-17 Created: 2016-11-11 Last updated: 2017-05-29Bibliographically approved

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