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  • 1.
    Amofah, Lea Rastas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    A small scale wastewater treatment system adapted to nutrient recovery in cold climate: performance and possible sorbents2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Waterbodies are impaired by, among other things, discharge from onsite small- scale wastewater (WW) treatment systems. Hence, these systems need to be updated to improve the effluent quality and the reuse of nutrients within society. The objectives of this thesis were to find suitable sorbents for a small scale WW treatment system, to investigate the performance of a willow bed in cold climate and to evaluate the function of a proposed WW treatment system adapted to sustainable development in cold climate.Column experiments were performed to study the ammonium adsorption and desorption of clinoptilolite. Laboratory scale studies were conducted to estimate the phosphorus (P) retention of blast furnace slag (BF slag). Further, a full-scale WW treatment system was implemented in northern Sweden to evaluate the function of the system and its units over 16 months. The system comprised of a willow bed and two parallel P filters, namely BF slag and Filtralite-P. A stream of primarily treated WW from a village was pumped to the treatment system.The results from the column experiments showed that ammonium adsorption of the studied clinoptilolite and the desorption of previously adsorbed ammonium was too low to be an economically reasonable alternative for WW ammonium retention in small-scale WW treatment systems.The investigated weathered and coarse-grained BF slag had a low WW P retention, with the overall P sorption below 100 mg P/kg. Therefore, the material is not suitable for P retention. Fresh and fine-grained BF slag demonstrated to be an effective P sorbent in laboratory experiments. However, the release of sulphuric compounds from the BF slag was extensive and may hinder its utilisation as P sorbent.Filtralite-P was found to be a promising P sorbent with a WW P sorption of about 370 mg P/kg at the end of the full-scale experimental period, and still with remaining capacity to retain P.The willow bed functioned as a treatment step due the reduction of nutrients, solids and BOD, and there was no significant difference in winter and summer performance. Climatic conditions seemed not to be a hindrance for willow beds in northern Sweden. However, the stemwood produced in the willow bed would replace only a small fraction of a household’s energy need for heating and warm water.In the full-scale study, the treatment system with BF slag filter attained neither of the protection levels given by Swedish Environmental Protection Agency (SEPA) during the experimental period. The Filtralite-P treatment line fulfilled the requirements of the low protection level by SEPA for the 1 year operating period and the requirements of the high protection level for 2 months. The need of maintanance in the studied treatment system was small and the operation was steady.

  • 2.
    Amofah, Lea Rastas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Towards sustainability of environmental protection: recovery of nutrients from wastewater filtration and the washing of arsenic contaminated soils2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Conventional methods for wastewater treatment and remediation of the sites withcontaminated soils focus on protection of human health, receiving waters and theenvironment. Towards this end, these methods concentrate on the reduction or removal of polluting substances, and therefore, are not well suited for creating resources through the recovery of nutrients, energy and decontaminated soils. Hence, a new, more sustainable approach is promoted in this thesis and, besides meeting the protection requirements, takes into consideration the resources that can be recovered from the treatment processes, keeping in mind the energy use during such a recovery. To achieve this goal, a better knowledge of wastewater and contaminated soil treatment approaches needs to be developed, from a resource recovery perspective.In this thesis project, laboratory, pilot-scale and full-scale investigations were conducted to study phosphorus (P) sorption in blast furnace slag (BF slag) filters. Further, ammonium adsorption by, and desorption from, clinoptilolite was studied in laboratory columns. A full-scale wastewater treatment system, comprising a willow bed followed by two parallel P–filters with BF slag and Filtralite® P media was examined for the wastewater treatment efficiency, nutrient accumulation in willow biomass, and biomass production. In a similar way, laboratory, pilot-scale and full-scale investigations were conducted to examine arsenic (As) removal from As contaminated soils using physical separation and chemical extraction. Finally, the decontamination of the extraction effluents (contaminated by As) was studied by adjusting pH and adding a coagulant, iron chloride.Pollutant mobilisation and immobilisation were affected by pH, the organic mattercontent, redox potential, time (process duration) and temperature. Results showed that pollutants in the studied media have complex characteristics in terms of charge of species and redox speciation, and therefore, no general conclusions addressing all the conditions studied could be given. The P sorption capacity of BF slag was reduced by outdoor storage and weathering, and the content of organic substances in sewage seemed to have a more negative impact on the sorption process when using weathered BF slag. Arsenic mobilisation from As contaminated soils was affected by pH, the content of organic substances, and redox potential and the nature of these effects depended on the polluting chemicals (i.e. wood preservatives) and the content of calcium in the soil. Extractions at elevated temperatures facilitated high As mobilisation from the contaminated soils for short contact times, assuming that the extraction solution features vital for As mobilisation were not altered, and the fastest As mobilisation was achieved by using an acid oxalate citrate solution rather than reductive or alkaline extraction solutions at room temperatures.In the full-scale treatment system, the willow bed efficiently reduced the content of total suspended solids and biodegradable organic matter in the influent wastewater and prevented the clogging of downstream phosphorus filters during the one year of operation. The Filtralite® P treatment train simultaneously removed over 90 and 70% of BOD and P, respectively, during the experimental period, and therefore, fulfilled the requirements for the low protection level over the period of one year, except for tot-P excesses during the snowmelt period. In the case of tot-N reduction (50%), the high protection level was achieved. On the other hand, the treatment system with BF slag did not fulfil requirements for either low or high protection level, because the coarse-grained BF slag was inefficient in retaining P and the concentrations of oxygen consuming compounds were elevated downstream of the filter.The studied methods for recovering resources through treatment of wastewater and contaminated soils demonstrated a potential for improving environmental sustainability of these processes. Even though the willow bed did not accumulate nutrients from the fed wastewater to a high degree, it facilitated nutrient recovery in other treatment steps located downstream. Fresh, fine-grained BF slag showed capacity to recover P from wastewater, which was comparable to that of other efficient P sorbents. The BF slag material released high amounts of sulphuric compounds during the initial loading phase which consequently increased the concentration of oxygen consuming compounds in the filter effluent. Thus, the use of BF slag for P retention is not recommended when the effluent is discharged to sensitive receiving waters. Natural clinoptilolite studied showed a high capacity for adsorbing ammonium from the pre-treated wastewater, at low operating temperatures. Hence, the clinoptilolite filter has a potential to enhance N retention during the plant dormancy or prior to the maturity of willow beds when N retention is needed. However, the recovery of ammonium was limited by the inefficient desorption process using tap water without recycling the eluate. Fertigated willows grew nearly as well as in the south of Sweden, but in the highly loaded horizontal flow willow bed, the potential to produce biofuel was limited. To recover nutrients, willow clones with lateral growth are preferable. 90% of nutrients accumulated in the above-ground parts of willows could be recovered from the experimental site operated over three growing seasons, particularly when using dense planting and annual harvesting prior to leaf fall.Soil treatment, comprising the exclusion of the fine soil fraction prior to the chemical extraction with strong extraction agents applied at an elevated temperature, was efficient in decontaminating soils, even for short contact times. However, this treatment procedure results in an incomplete soil recovery (i.e. the recovered mass of soil after decontamination is appreciably smaller than the soil mass prior to decontamination), consumes a high amount of energy and lowers the soil quality, which limits the potential end-use of the decontaminated soil. The alkaline extraction effluents could be decontaminated at a pH of 4-5 with the addition of a coagulant. Also, the treatment of alkaline extraction effluents was facilitated by the exclusion of the fine soil fraction from the chemical extraction step. The use of acid oxalate-citrate extraction solution was judged infeasible because the decontamination of such extraction solution is complicated due to the high pH buffering and complexing capacity of the solution.

  • 3.
    Amofah, Lea Rastas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Hanaeus, Jörgen
    Nutrient recovery in a smallscale wastewater treatment plant in cold climate2006Inngår i: Vatten, ISSN 0042-2886, Vol. 62, nr 4, s. 355-368Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    An onsite wastewater treatment plant at Brändön, north of Luleå, receiving primarily treated wastewater from a village, was operated and investigated during one year. The wastewater flow was 0.5 m3/d. The main treatment steps were a prefilter, mainly to distribute the flow, a vegetation filter consisting of two different clones of Salix and two phosphorus filters with Filtralite-P and blast furnace slag (BF slag) operated in parallel. The willow bed reduction of BOD7 was in average about 80% and of phosphorus (P) and nitrogen (N) 20-30%. The main mechanism was believed to be filtration in the bed. The reduction through plant uptake was minor. The Filtralite-P filter reduced BOD7, P and N with 67%, 72% and 20%, respectively. The BF slag filter reduced P and N with 53% and 3%, respectively. The release of sulphuric compounds from the BF slag filter increased the BOD7 content in the effluent. The Filtralite-P system achieved the requirements of the normal protection level given by the Swedish Environmental Protection Agency but not all of the requirements of the high protection level. The BF slag system did not fullfil the requirements of the two protection levels.

  • 4.
    Amofah, Lea Rastas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Mattsson, Jonathan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Hedström, Annelie
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Willow bed fertigated with domestic wastewater to recover nutrients in subarctic climates2012Inngår i: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 47, s. 174-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional methods for wastewater treatment emphasise protecting human health, receiving waters and the environment. Consequently, they are generally designed to reduce pollutant levels and are not well-suited for creating resources. This paper describes a new, more sustainable and energy-efficient approach to wastewater treatment that satisfies health and environmental standards while also facilitating resource recovery. A full-scale compact willow bed was intensively fertigated with domestic wastewater in a cold climate to examine biomass production, the recovery of nutrients in willow biomass, and wastewater treatment. The performance of the willow bed was assessed for two years, covering three growing seasons. The studied frost-tolerant willow clones produced good biomass yields per unit area (6–7 ton dry matter/ha and year) under intensive fertigation with dense planting and continuous harvesting. The biomass yield of willow species exhibiting vertical growth seemed to be greater than that for lateral growth species in the dense stands studied. In contrast to biomass production, nutrient recovery was facilitated by intensive fertigation, continuous harvesting and less dense planting with a horizontally growing willow clone. The estimated nitrogen accumulation in above-ground biomass was 210 kg/ha and that of phosphorus was 30 kg/ha. 90% of the accumulated nutrients in the above-ground biomass were removed from the site during the experimental period. However, the quantity of nutrients accumulated in the willow biomass represented only a small fraction of the loaded or removed amount. The willow bed was shown to be an efficient prefilter for reducing the abundance of particulate and organic matter, leaving the bulk of the remaining nutrients in forms that could be recovered in subsequent treatment steps.

  • 5.
    Amofah, Lea Rastas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bhattacharya, Prosun
    Kungliga tekniska högskolan, KTH.
    Chemical extraction of As from a polluted soil2008Inngår i: Arsenic in the environment - Arsenic from nature to humans: Book of Abstracts, 2008, s. 205-Konferansepaper (Annet vitenskapelig)
  • 6.
    Amofah, Lea Rastas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bhattacharya, Prosun
    KTH-International Groundwater Arsenic Research Group, Department of Land and Water Resources Engineering, Royal Institute of Technology (KTH),.
    Extraction of arsenic from soils contaminated with wood preservation chemicals2010Inngår i: Soil & sediment contamination, ISSN 1532-0383, E-ISSN 1549-7887, Vol. 19, nr 2, s. 142-159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three soil samples contaminated by chromated zinc arsenate (CZA) or chromated copper arsenate (CCA) were investigated in a laboratory scale to study As mobilization and to identify a chemical agent that could be used in soil washing to extract arsenic. Besides high As extraction, the cost, occupational health issues and technical aspects were considered when selecting the chemical. Arsenic is strongly bound to CZA/CCA soils; only ∼50% of the tot-As was removed from water-washed soils. High Fe or Al mobilization is not necessarily indicative of high As removal from CZA/CCA soils. A high Cu/As-ratio and a large amount of soluble Ca in the soil hampered As extraction. The high ratio can be an indication of stable Cu-arsenates in soil. Calcium can react with the extraction agent or with As during extraction. Sodium hydroxide, dithionite with citrate (and oxalate) (dithionite solutions), and oxalate with citrate were the most efficient chemicals for removing As from the soils. The disadvantages of using these strong chemicals are: a high cost (oxalate with citrate); damage to equipment (dithionite solutions); an adverse impact on occupational health (dithionite solutions); or a deterioration in soil quality after extraction (NaOH and dithionite solutons). Phosphate, solutions based on NH2OH·HCl, or citrate were not efficient in mobilizing As from the soils.

  • 7.
    Amofah, Lea Rastas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bhattacharya, Prosun
    Department of Land and Water Resources Engineering, Royal Institute of Technology.
    The influence of temperature, pH/molarity and extractant on the removal of arsenic, chromium and zinc from contaminated soil2011Inngår i: Journal of Soils and Sediments, ISSN 1439-0108, E-ISSN 1614-7480, Vol. 11, nr 8, s. 1334-1344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: Normal soil washing leave high residual pollutant content in soil. The remediation could be improved by targeting the extraction to coarser fractions. Further, a low/high extraction pH and higher temperature enhance the pollutant removal, but these measures are costly. In this study, the utility of NaOH, oxalate-citrate (OC) and dithionite-citrate-oxalate (DCO) solutions for extracting of arsenic, chromium and zinc from contaminated soil were assessed and compared. In addition the effects of NaOH concentration and temperature on NaOH extractions, and those of temperature and pH on OC and DCO extractions, were evaluated. Materials and methods: A two-level, full-factorial design with a centre point was implemented. Two factors, concentration and temperature,were evaluated in NaOH extractions, and pH and temperature for OC and DCO solutions. In all cases, the extraction temperature was 20°C, 30°C and 40°C. The studied NaOH concentrations were 0.05, 0.075 and 0.1 M. The pH in OC solutions was 3, 5 and 7, and in DCO solutions, 4.7, 6.3 and 6.7. Water-washed and medium coarse soil fraction of arsenic, chromium and zinc contaminated soil was agitated for 15 min with the extraction solution. Results and discussion: In NaOH extractions, the temperature and (less strongly) NaOH concentration significantly affected As and Cr mobilisation, but only the latter affected Zn mobilisation. Both pH and temperature significantly (and similarly) influenced As and Cr mobilisation in OC extractions, while only the pH influenced Zn mobilisation. In contrast, the extraction temperature (but not pH) influenced As, Cr and Zn mobilisation in DCO extractions. Conclusions: For all extractants, mobilisation was most efficient at elevated temperature (40°C). None of the extractants reduced the soil's As content to below the Swedish EPA's guideline value. Use of DCO is not recommended because dithionite has a short lifetime and residual arsenic contents in DCO-extracted soil are relatively high. Instead, sequential extraction with NaOH followed by OC solutions (affording significant reductions in As, Cr and Zn levels in the soil with short extraction times) at 40°C is recommended

  • 8.
    Hedström, Annelie
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Amofah, Lea Rastas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Adsorption and desorption of ammonium by clinoptilolite adsorbent in municipal wastewater treatment systems2008Inngår i: Journal of Environmental Engineering and Science, ISSN 1496-2551, E-ISSN 1496-256X, Vol. 7, nr 1, s. 53-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Natural zeolites as clinoptilolite may be used to recover wastewater ammonium, decrease the nitrogen content in the effluent from on-site sanitation systems and in wastewater treatment plants when nitrification-denitrification efficiency is low. The objective of this study was to estimate the ammonium adsorption capacity of clinoptilolite when being loaded with wastewater. Phosphorus and potassium sorption, ammonium desorption with tap water, and clogging were also studied. The study was performed by column experiments. Results of the investigation showed the ammonium adsorption capacity to increase with decreasing grain size, and the highest experimental adsorption capacity was 2.7 mg NH4-N/g. The breakthrough occurred immediately, probably due to a too high loading rate. Phosphorus and potassium sorption were minor. Of adsorbed ammonium, 23% was desorbed by tap water and desorption was more pronounced during saturated conditions. Filter clogging was extensive and probably caused by particles in the effluent wastewater and by microbiological growth.

  • 9.
    Hedström, Annelie
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Amofah, Lea Rastas
    Methodological aspects of using blast furnace slag for wastewater phosphorus removal2006Inngår i: Journal of environmental engineering, ISSN 0733-9372, E-ISSN 1943-7870, Vol. 132, nr 11, s. 1431-1438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blast furnace (BF) slag is a by-product of steel plants. The objective of this study was to evaluate experimental methods to determine the phosphorus sorption capacity of BF slag. The handling of BF slag, before usage and clogging were also considered, as well as estimating the phosphorus retention capacity. Agitation and pilot-scale experiments were performed using both wastewater and phosphate solutions. This investigation showed that sorption capacities derived by wastewater experiments were considerably lower compared to those by phosphate solutions. Fresh BF slag briefly exposed to rainfall had a higher phosphorus sorption than weathered BF slag, indicating the importance of handling the slag carefully before usage. The risk for leakage of sulfuric compounds is considerable, especially during the initial operation phase of BF slag filters. Locations of BF slag filter beds for wastewater treatment must be carefully chosen from an environmental point of view.

  • 10.
    Hedström, Annelie
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Amofah, Lea Rastas
    Hanaeus, Jörgen
    Småskalig avloppsanläggning med salixbädd och sorbenter2007Rapport (Annet vitenskapelig)
    Abstract [en]

    In residential and rural areas in Sweden, a considerable number of houses are not connected to municipal wastewater treatment plants but the wastewater is treated in on-site sanitation systems. These systems contribute significantly to the anthropogenic discharge of phosphorus. Therefore, further development of small scale wastewater treatment systems is necessary. The aim of this project was to develop a small-scale wastewater treatment system to facilitate nutrient recovery. A full-scale experimental system with two treatment lines for a total flow of 1 m3/d was built. Investigated components of the system were a distribution layer, a willow bed with a root zone, followed by two parallel containers filled with filter materials for sorption of phosphorus. Filter material investigated in full-scale were Filtralite P and blast furnace (BF) slag. Besides the full-scale investigation, filter materials were investigated in laboratory. BF slag was investigated with respect to phosphorus sorption, wollastonite with respect to phosphorus and ammonium sorption and clinoptilolite with respect to ammonium adsorption.In the full-scale experiment suspended solids and organic matter was effectively reduced in the willow bed. The reduction of SS was 93% in average and the reduction of BOD was 86%. The effluent wastewater from the willow bed was sufficiently treated to avoid clogging of the following phosphorus filters. However, the nutrient reduction in the willow bed was moderate. The reduction of both total nitrogen and total phosphorus varied between 10 and 60%.The filter volume of Filtralite P and BF slag used in the full-scale investigation, 2,2 m3, was too small to achieve an efficient phosphorus reduction during one year. The investigated fresh slag sorbed more phosphorus compared to weathered slag. Thus, if the slag is covered during storage to prevent active substances to be leached out by precipitation, the phosphorus sorption of the slag will probably be preserved. BF slag contains sulphuric compounds. In both the laboratory and the full-scale studies, sulphuric compounds leached out when wastewater percolated through the filter. This can be a hinder for using BF slag in a wastewater treatment system.The investigated wollastonite and clinoptilolite can not be recommended to be used in small-scale wastewater treatment with respect to phosphorus and ammonium sorption. The investigated willow clones "Karin" and "Gudrun" could be establish as far north as in Luleå. The biomass production of the second growing season was as high as for salix clones with wastewater in southern Scandinavia.A willow bed combined with a phosphorus filter could be a robust small-scale wastewater treatment method but some components must be further developed.

  • 11. Rastas Amofah, Lea
    et al.
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Prosun, Bhattacharya
    Department of Land and Water Resources Engineering, Royal Institute of Technology, Sverige.
    Projekt: Pilotskale utvärdering av jordtvätt för sanering av arsenik-kontaminerad jord2011Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    Jordtvätt - en lämplig metod för behandling av CCA förorenad jord? I samband med Länsstyrelsernas kartläggning av förorenade områden har upptäckts objekt som är förorenade med arsenik. En del av objekt är så förorenade att de har negativ påverkan på miljön eller människors hälsa så att de behöver åtgärdas senast år 2010. I träimpregneringsindustrin användes kromerad koppar arsenat (CCA) som impregneringsmedel. Olika steg i impregneringsprocessen har lett till att jord förorenats med As. Deponering är idag en vanlig metod att omhänderta arsenikförorenad jord och en betydande del av efterbehandlingskostnaderna består ofta av transport- och deponeringsavgifter. Nyligen har regelverk för bedömning av avfall förändrats vilket har banat väg för nya behandlingsmetoder för förorenad jord såsom jordtvätt. Huvudsyftet med detta projekt är att bedöma om jordtvätt är en lämplig behandlingsmetod för CCA-förorenad jord. Andra syften med projektet är att hitta en lämplig kemikalietillsats för att höja metodens effektivitet samt att hitta en effektiv metod att behandla As förorenad tvättvätska. Kan man säkerställa att den behandlade jorden är stabil och inte har några negativa effekter på omgivningen kan det bidra till att etablera jordtvätt som en hållbar behandlingsmetod. Deponering av jord är varken en hållbar eller en effektiv användning av resurser. Behandling av föroreningarna och återanvändning av det behandlade jordmaterialet kan däremot leda till minskad förbrukning av jord, minskade transporter, etc.

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