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  • 1.
    Hamisi, Rajabu
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Filtration System For On-Site Wastewater Treatment: Experiences From Modelling and Experimental Investigations2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Many on-site wastewater treatment systems in Sweden are not sustainable in terms of treatment efficiency, nutrient recycling and economics. Achieving reliable and sustainable systems to meet on-site wastewater treatment demands requires comprehensive field investigations of the performance of novel technologies. This thesis investigated the performance of a new leading-edge technology for on-site wastewater treatment in a real field environment in northwest of Baltic Proper Sea, Sweden. The system integrates septic tank treatment technology with a package treatment plant (PTP) and a sequencing batch subsurface flow constructed wetland (SBCW). The investigation combined three approaches: field monitoring, laboratory-scale column experiments and process-based modelling, to provide a better understanding of system performance, predict contaminant retention and test system response to various environmental factors, design scenarios and operational conditions.

    The overall results indicated that the entire system is efficient in removing total phosphorus (83%), biological oxygen demand (BOD7, 99%) and Escherichia coli bacteria (89%). It is less efficient in total inorganic nitrogen removal (22%). Mean concentration of phosphorus (0.96 mg/L) and pH (8.8) in effluent from the entire system were found to be below the Swedish threshold values for on-site wastewater discharge. This indicates that the system could be reliable and sustainable technology for on-site wastewater treatment in cold climate conditions.

    A complementary three-dimensional (3D) model developed using COMSOL Multiphysics® software proved to be a useful and rapid tool for predicting the behaviour of complex hydraulic dynamics. It provided valuable insights into the spatial and temporal variability in sorption processes caused by changes in different wastewater treatment system design parameters, environmental factors and modes of operation. Through process-based modelling, a reactive filter material with longer lifetime and a SBCW design that improved the sustainability of on-site wastewater treatment system were successfully identified.

    It was concluded that long-term performance of reactive filter materials in PTP systems can be achieved when the system is loaded intermittently with low influent contaminant concentrations (<3 mg/L). Optimum phosphorus and nitrogen removal in SBCW can be achieved by manipulating drainage pipe placement and feeding mode, to enable longer contact time and artificial aeration conditions.

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  • 2.
    Hamisi, Rajabu
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Modelling phosphorus dynamics in constructed wetlands upgraded with reactive filter media2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Developing low-cost and effective technologies to upgrade phosphorus (P) removal from the catchment runoffs and rural wastewater treatment facilities is one of the main research agendas to save the Baltic Sea from eutrophication. In Sweden, the construction of the constructed wetlands has been one of the environmental objectives for wastewater quality improvement in the small communities. However, the insufficiently understanding of the mechanisms underlying the process of phosphorus mobility and sorption in the constructed wetlands has limited design of the effective constructed wetlands. To provide the better understanding of sorption process in the catchment and constructed wetland system, this thesis used the GIS-based Soil and Water Assessment Tool (SWAT) to predict phosphorus mobility and identify the critical diffusing sources of phosphorus loss in the Oxunda catchment (Paper I). Then, the study developed the three-dimensional numerical Reactive TRAnsPort Model (RETRAP - 3D) in the COMSOL Multiphysics® for evaluating the long - term sorption processes and removal efficiencies of the porous reactive media for upgrading the performance of constructed wetlands (Paper II and III). The latter model coupled many physics equations to solve process of water flow, reaction kinetics and solute transport in the porous reactive adsorbent media for application in the constructed wetlands. The data from the field measurements and column experiments have been used to demonstrate the model simulation accuracy to capture the process of phosphorus sorption in the real environment. Modeling results ranked the phosphorus removal efficiency of the adsorbent media as follows: Polonite® (88 %), Filtralite P® (85%), BFS (62%), Wollastonite (57 %). The satisfactory agreement which obtained between the simulated outputs and measured data confirmed that the SWAT and RETRAP-3D are useful tools for describing various processes in the complicated system. However, further study is required to generate and validate more experimental data to evaluate the sensitivity of local parameters.

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  • 3.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Jansson, Per-Erik
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Hamerlynck, O
    Duvail, S
    Applications of Process Base Models for Sustainable Water Utilizations in a Competing Demands and Climate Variability: A Case of the Lower Rufiji, Tanzania2013Conference paper (Refereed)
  • 4.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Performance of an On-Site Wastewater Treatment System Using Reactive Filter Media and a Sequencing Batch Constructed Wetland2019In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, no 11, article id UNSP 3172Article in journal (Refereed)
    Abstract [en]

    Many on-site wastewater treatment systems, such as soil treatment systems, are not sustainable in terms of purification efficiency, nutrient recycling potential, and economics. In this case study, a sequencing batch constructed wetland (SBCW) was designed and added after a package treatment plant (PTP) using reactive filter media for phosphorus (P) removal and recycling. The treatment performance of the entire system in the start-up phase and its possible applicability in rural areas were investigated. Raw and treated effluents were sampled during a period of 25 weeks and analyzed for nitrogen, phosphorus, BOD7, and bacteria. Field measurements were made of wastewater flow, electrical conductivity, oxygen, and temperature. The entire system removed total-P and total inorganic nitrogen (TIN) by 83% and 22%, respectively. High salt concentration and very low wastewater temperature were possible reasons for these unexpectedly low P and TIN removal efficiencies. In contrast, removal rates of bacteria (Escherichia coli, enterococci) and organic matter (as BOD) were high, due to filtration in the alkaline medium Polonite((R)) (Ecofiltration Nordic AB, Stockholm, Sweden) and the fine sand used as SBCW substrate. High pH in effluent from the PTP was efficiently reduced to below pH 9 in the SBCW, meeting recommendations by environmental authorities in Sweden. We concluded that treating cold on-site wastewater can impair treatment performance and that technical measures are needed to improve SBCW performance.

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  • 5.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Brokking Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    A new modelling approach for phosphorus mobility and retention processes in the Oxundaån catchment, SwedenManuscript (preprint) (Other academic)
    Abstract [en]

    Eutrophication is the most significant threat towater quality in the entire Baltic Sea region. Its causes are nutrientover-enrichment from diffuse and point sources. Thematic strategies forsustainable mitigation of phosphorus loss from sewage drainage systems andrunoffs from arable land require a holistic approach to identify the criticalpolluting sources and implement relevant policy for adaptive water qualitymanagement. The use of constructed wetlands constitutes one such strategy thatcan mitigate phosphorus loss. However, insufficient understanding about phosphorusmobility and retention in catchments significantly hinders efforts to identifysuitable sites for constructed wetlands and implement alternative, adaptive andeffective management actions. This study aims to evaluate the long-termphosphorus mobility and retention in the Oxudaån catchment in Sweden, andthereby propose suitable sites to localize constructed wetlands. The Soil andWater Assessment watershed model was applied to map and quantify the phosphorusloading from diffuse and point sources under the scenarios of land usemanagement practices. Simulation results have demonstrated the positivecorrelation between the phosphorus concentration with the surface runoffs andnegative correlation with the pH. Overall, Oxundaån catchment indicates a decreasingtrend of phosphorus loading in the Verkaån and Oxundaån riverine of around 2.1% and 1.3 % per year, respectively. The present study suggests the suitablesites for localizing constructed wetlands in the south-west and north-east ofOxundaån lake based on the factor of low slope topography and soilpermeability. The simulation results from the SWAT model offer evidence thatcan guide the localization and choice of management interventions to achieve asustainable mitigation of phosphorus loss. This study concludes that, while singlemanagement actions can help solve the problem of eutrophication, a moreeffective and sustainable mitigation of eutrophication will require the integrationof multiple adaptive land use management approaches.

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  • 6.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Brokking Balfors, Berit
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Welin, Anders
    SWECO International AB, Stockholm, Sweden.
    Larm, Thomas
    Modelling phosphorus recovery by reactive adsorbent in a vertical subsurface flow constructed wetlandManuscript (preprint) (Other academic)
    Abstract [en]

    Phosphorus removal efficiencies by four low - costsreactive adsorbent media were evaluated in the long - time period using thethree - dimensional model of the vertical subsurface flow constructed wetlandsin the COMSOL Multiphysics® software. Evaluations were made for Polonite,Filtralite P, Sorbulite and Wollastonite adsorbent media with the aims ofpredicting their long - term sorption capacity and describing the phenomena ofsorption mechanisms when applied in the vertical subsurface flow constructedwetlands for wastewater purification. The 3D model of the vertical flowconstructed wetlands were dimensioned to Swedish EPA guidelines for small scalewastewater treatment, and calibrated at saturated media using the breakthroughdata derived from the column experiments of similar adsorbent mediaapplication, and the local sensitivity analysis were performed for waterquality and hydraulic loading parameters. It was observed that the breakthroughcurves developed by model were significantly correlated to the experimentaldata. The overall findings showed that Polonite® could be the potentialreactive adsorbent for phosphorus removal in the VF-CWs application, and itsremoval efficiency was discovered to last for 5 years. The large variation ofmedia sorption capacities discovered to be affected more by factor of pH andhydraulic loading rates than the particle size. High degree of predictionaccuracy which is demonstrated by this model suggest that the proposed model isa useful tool for predicting pollutants removal in various reactive porousmedia.

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  • 7.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Herrmann, Inga
    Department of Civil, Environmental and Natural Resources Engineering.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. SEED-KTH.
    Reactive transport modelling of long-term phosphorus dynamic in the compact constructed   wetland using COMSOL MultiphysicsIn: Ecological Engineering JournalArticle in journal (Other academic)
    Abstract [en]

    A three-dimensional reactive transport model (RETRAP-3D) was developed by this study in the COMSOL Multiphysics®software to evaluate the long-term sorption capacity and mechanisms of dissolved reactive phosphorus removal in reactive adsorbent. The model coupledphysics interfaces for water flow, transport of reactive species, reaction kinetics for chemical compositions and biofilm development. Simulations were conducted for Polonite®, Filtralite P®, and Blast Furnace Slag mediaat fully saturated media, equilibrium miscible solution and isothermal heat transfer conditions. The model was validated using column experimental data ofsimilar media for application in constructed filter beds. The general modelling results showed good agreement with the measured breakthrough data. The most significant DIP retention capacity (P < 0.02) and longest residence time(1250 days) has been found for Polonite® and the most insignificant DIP retention for blast furnace slag (P > 0.54). The DIP removal was significantly correlated to factors of pH change, media characteristics, hydraulic dosage and retention times. These results demonstrate the reliability of the model as aflexible tool to predict the long-term performance of filter media and better understand processes within the system under various operational, weather and wastewater conditions.

  • 8.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Modelling Phosphorus Sorption Kinetics and the Longevity of Reactive Filter Materials Used for On-site Wastewater Treatment2019In: Water, Vol. 11, no 4, article id 811Article in journal (Refereed)
    Abstract [en]

    Use of reactive filter media (RFM) is an emerging technology in small-scale wastewater treatment to improve phosphorus (P) removal and filter material longevity for making this technology sustainable. In this study, long-term sorption kinetics and the spatial dynamics of sorbed P distribution were simulated in replaceable P-filter bags filled with 700 L of reactive material and used in real on-site treatment systems. The input data for model calibration were obtained in laboratory trials with Filtralite P®, Polonite® and Top16. The P concentration breakthrough threshold value was set at an effluent/influent (C/C0) ratio of 1 and simulations were performed with P concentrations varying from 1 to 25 mg L−1. The simulation results showed that influent P concentration was important for the breakthrough and longevity, and that Polonite performed best, followed by Top16 and Filtralite P. A 100-day break in simulated intermittent flow allowed the materials to recover, which for Polonite involved slight retardation of P saturation. The simulated spatial distribution of P accumulated in the filter bags showed large differences between the filter materials. The modelling insights from this study can be applied in design and operation of on-site treatment systems using reactive filter materials

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  • 9.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Modelling phosphorus sorption kinetics and the longevity of reactive filter materials used for on-sitewastewater treatment2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 4, article id 811Article in journal (Refereed)
    Abstract [en]

    Use of reactive filter media (RFM) is an emerging technology in small-scale wastewater treatment to improve phosphorus (P) removal and filter material longevity for making this technology sustainable. In this study, long-term sorption kinetics and the spatial dynamics of sorbed P distribution were simulated in replaceable P-filter bags filled with 700 L of reactive material and used in real on-site treatment systems. The input data for model calibration were obtained in laboratory trials with Filtralite P®, Polonite® and Top16. The P concentration breakthrough threshold value was set at an effluent/influent (C/C 0 ) ratio of 1 and simulations were performed with P concentrations varying from 1 to 25 mg L -1 . The simulation results showed that influent P concentration was important for the breakthrough and longevity, and that Polonite performed best, followed by Top16 and Filtralite P. A 100-day break in simulated intermittent flow allowed the materials to recover, which for Polonite involved slight retardation of P saturation. The simulated spatial distribution of P accumulated in the filter bags showed large differences between the filter materials. The modelling insights from this study can be applied in design and operation of on-site treatment systems using reactive filter materials.

  • 10.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Phosphorus sorption and leaching in sand filters used for onsite wastewater treatment - a column experimentIn: Article, book review (Refereed)
    Abstract [en]

    The sorption capacities of filter sands used for onsite wastewater treatment and their associated risks of phosphorus (P) leakage on contact with rainwater were investigated in column experiments and modelling studies. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to artificial rainwater. The results indicated that sand columns can exhibit different adsorption capacities for Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater. The adsorption capacity increased in the order ST > BF > PO, based on availability of organic matter to form biofilm. Effluent from Pol columns was significantly clearer, indicating lower organics content, than effluent from ST and BF columns. The modelled breakthrough curves for Total-P desorption agreed satisfactorily with the measured values, but further model improvement is needed.

  • 11.
    Hamisi, Rajabu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Renman, Agnieszka
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Simulating the hydraulic dynamics and treatment performance of a sequencing batch flow constructed wetlandIn: Article, book review (Refereed)
    Abstract [en]

    In a six-month field trial, the performance of a full-scale sequencing batch flow constructed wetland (SBCW) treating on-site wastewater was determined. The filling and draining periods lasted 5-9 days, depending on wastewater production by users (two households). The results indicated that the SBCW system efficiently removed ammonium-nitrogen (NH4-N, 76%) and Escherichia coli (89%). However, draining by pumping increased preferential water flow and considerably limited removal of dissolved phosphorus (PO4-P) in the filter bed. Analysis of water samples from nine points and three vertical levels of the wetland bed showed that pumping aerated the bed, resulting in removal of NH4-N being highest in the top 0-0.2 m layer (43%) intermediate in the 0.2-0.4 m layer (32%), and lowest in the deep (0.4-0.6 m) layer (4%). Complementary modeling using COMSOL Multiphysics software to predict the hydraulic dynamics for three different SBCW designs indicated that the drainage system of the present SBCW should be re-designed to increase contact time and aeration, for improved phosphorus and nitrogen removal.

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