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Phosphorus removal in reactive filter materials: factors affecting the sorption capacity
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Phosphorus is an essential component in all living organisms; it is one of the components of the DNA and the key element in the energy supplying molecule adenosine triphosphate (ATP). Throughout the history, humans have been recycling phosphorus to agriculture; thereby increasing the yield, examples of this includes the burning of plants and the use of manure. Today, we rely on commercial fertilizers with high concentrations of phosphorus. The manufacturing of these products include extraction of phosphorus from phosphate rock. However, phosphate rock is a limited and non-renewable resource and the reserves are declining. The population on our planet in constantly increasing, hence the shortage of fertilizers would have consequences of catastrophic measurements, the most obvious being starvation. In order to avoid this scenario it is of uttermost importance to reuse the phosphorus that passes through our society and is subsequently released in the wastewater. The inadequate small-scale wastewater treatment facilities in Sweden of today are contributing with 20% to the release of phosphorus. By implementing the use of reactive filter materials in these systems, direct release of phosphorus to the recipient can be prevented. After a period of time these materials have to be exchanged, and they can thereafter be used as fertilizers, thereby re-cycling the phosphorus back to agriculture.

The effectiveness of the reactive materials is affected by several parameters, such as pH, specific surface area, hydraulic properties of the material and the characteristics and distribution of the wastewater. In order to compare the phosphorus retention capacity in three different materials, two experiments utilizing septic-tank wastewater was conducted. The first was a pilot-scale-experiment that included Polonite and blast furnace slag (BFS) as filter materials. This experiment was conducted in two phases, using wastewater with high respectively low concentrations of organic matter. The study investigated the effect of organic matter on the phosphorus retention capacity in the materials; additionally the reduction of indicator bacteria (Enterococci) and organic matter (TOC) was studied. The second experiment was conducted at the laboratory, using wastewater with high concentrations of organic matter. In this study, the phosphate retention capacity in Polonite and Sorbulite was investigated in a re-circulatory system, where the treated wastewater was re-circulated back to the influent volume of water. The additional parameters investigated in this experiment were the removal of nitrogen and TOC as well as the retention of indicator bacteria (E. coli and Enterococci).

The results showed that Polonite performed better compared to the other materials with regards to the removal of phosphate, total phosphorus and bacteria. Sorbulite had a higher removal rate of TOC and total inorganic nitrogen (TIN) compared to Polonite, which in turn removed more TOC than BFS. Furthermore, both Polonite and BFS had a higher phosphorus retention capacity when using wastewater with low concentrations of organic matter. These two materials showed a higher percentage reduction of indicator bacteria when using wastewater with high concentrations of organic matter. However, since the results showed that the bacteria count in the effluent was lower when using wastewater with low concentrations of organic matter, the higher reduction rate was therefore ascribed to a higher concentration of bacteria in wastewater with high concentrations of organic matter. Therefore, the conclusion was drawn that low concentrations of organic matter is preferable also in respect of bacteria reduction. In order to ensure a high removal of phosphorus and bacteria, as well as to prolong the lifetime of the filter material, the wastewater should be pre-treated to obtain a BOD7 value below 20 mg L-1.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xii, 22 p.
Series
Trita-LWR. LIC, ISSN 1650-8629 ; 2066
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-104730ISBN: 978-91-7501-556-9 (print)OAI: oai:DiVA.org:kth-104730DiVA: diva2:566812
Presentation
2012-11-30, V35, Teknikringen 76, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20121109

Available from: 2012-11-09 Created: 2012-11-09 Last updated: 2013-11-21Bibliographically approved
List of papers
1. Effect of organic load on phosphorus and bacteria removal from wastewater using alkaline filter materials
Open this publication in new window or tab >>Effect of organic load on phosphorus and bacteria removal from wastewater using alkaline filter materials
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2013 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 47, no 16, 6289-6297 p.Article in journal (Refereed) Published
Abstract [en]

The organic matter released from septic tanks can disturb the subsequent step in on-site wastewater treatment such as the innovative filters for phosphorus removal. This study investigated the effect of organic load on phosphorus (P) and bacteria removal by reactive filter materials under real-life treatment conditions. Two long-term column experiments were conducted at very short hydraulic residence times (average similar to 5.5 h), using wastewater with high (mean similar to 120 mg L-1) and low (mean similar to 20 mg L-1) BOD7 values. Two alkaline filter materials, the calcium-silicate material Polonite and blast furnace slag (BFS), were tested for the removal capacity of total P, total organic carbon (TOC) and Enterococci. Both experiments showed that Polonite removed P significantly ( p < 0.01) better than BFS. An increase in P removal efficiency of 29.3% was observed for the Polonite filter at the lower concentration of BOD7 ( p < 0.05). Polonite was also better than BFS with regard to removal of TOC, but there were no significant differences between the two filter materials with regard to removal of Enterococci. The reduction in Enterococci was greater in the experiment using wastewater with high BOD7, an effect attributable to the higher concentration of bacteria in that wastewater. Overall, the results demonstrate the importance of extensive pre-treatment of wastewater to achieve good phosphorus removal in reactive bed filters and prolonged filter life.

Keyword
Blast furnace slag, Calcium-silicate mineral, Column experiment, Enterococci, Total organic carbon
National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-104729 (URN)10.1016/j.watres.2013.08.001 (DOI)000326910000031 ()2-s2.0-84885371045 (Scopus ID)
Funder
Formas
Note

QC 20131209

Available from: 2012-11-09 Created: 2012-11-09 Last updated: 2017-12-07Bibliographically approved
2. Efficacy of reactive mineral-based sorbents for phosphate, bacteria, nitrogen and TOC removal - Column experiment in recirculation batch mode
Open this publication in new window or tab >>Efficacy of reactive mineral-based sorbents for phosphate, bacteria, nitrogen and TOC removal - Column experiment in recirculation batch mode
2013 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 47, no 14, 5165-5175 p.Article in journal (Refereed) Published
Abstract [en]

Two mineral-based materials (Polonite and Sorbulite) intended for filter wells in on-site wastewater treatment were compared in terms of removal of phosphate (PO4-P), total inorganic nitrogen (TIN), total organic carbon (TOC) and faecal indicator bacteria (Escherichia coli and Enterococci). Using an innovative, recirculating system, septic tank effluent was pumped at a hydraulic loading rate of 3000 L m(2) d(-1) into triplicate bench-scale columns of each material over a 90-day period. The results showed that Polonite performed better with respect to removal of PO4-P, retaining on average 80% compared with 75% in Sorbulite. This difference was attributed to higher CaO content in Polonite and its faster dissolution. Polonite also performed better in terms of removal of bacteria because of its higher pH value. The total average reduction in E. coli was 60% in Polonite and 45% in Sorbulite, while for Enterococci the corresponding value was 56% in Polonite and 34% in Sorbulite. Sorbulite removed TIN more effectively, with a removal rate of 23%, while Polonite removed 11% of TIN, as well as TOC. Organic matter (measured as TOC) was accumulated in the filter materials but was also released periodically. The results showed that Sorbulite could meet the demand in removing phosphate and nitrogen with reduced microbial release from the wastewater treatment process.

Keyword
Polonite, Sorbulite, Enterococci, Escherichia coli
National Category
Environmental Biotechnology Water Treatment
Identifiers
urn:nbn:se:kth:diva-131720 (URN)10.1016/j.watres.2013.05.056 (DOI)000324566400034 ()2-s2.0-84883285298 (Scopus ID)
Funder
Formas
Note

QC 20131018. Updated from "Manuscript" to "Article"

Available from: 2013-10-18 Created: 2013-10-17 Last updated: 2017-12-06Bibliographically approved

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