Jäteravinteet talteen: Typen ja fosforin talteenoton suunnittelu ja evaluaatio käyttäen kalvo- ja adsorptiotekniikkoja

Global food production relies on industrial fertilizers. The explosive growth of the human population would not have been possible without processes that bind nitrogen from the atmosphere to ammonia and mined phosphate rock to easily soluble products. However, the linear consumption pattern (as opposed to circular) has backfired on us. As a result, the nutrient systems we rely on consume significant amounts of energy and create an array of environmental problems. This dissertation focuses on the question: 'How can we close the nutrient loop?' Furthermore, special attention is paid to managing nutrient recycling in an environmentally and economically sustainable way. There is a vast quantity of nutrients available in different concentrated waste streams. However, these nutrients are not recycled efficiently because it is economically unfeasible or there are concerns about pollutants. These concerns apply to both liquid and solid waste streams. This dissertation is built around NPHarvest, a nutrient recovery technology developed at Aalto University. NPHarvest recovers both nitrogen and phosphorus from liquid waste streams with high efficiency. The end products are clean ammonia salt and solid material that contains phosphorus, calcium and carbon. The dissertation found that NPHarvest as a technology is economically competitive. The recovery process's novelty is how well it is designed to tolerate suspended solids in a wastewater environment and operate with low energy consumption, which decreases operational costs. Upon studying the life cycle assessment of the process, NPHarvest environmental performance was found to be positive or neutral in most impact categories. The process has the potential to be climate-positive (carbon-negative) with further optimization. Additionally, this dissertation examines P recovery from chemically precipitated sludge. It is technically possible, but not feasible enough, to be implemented on a large scale with currently available technologies. Waste-based biosolid materials proved to be a suitable pathway to capture phosphorus after acidleaching. The phosphorus-loaded biosolid can function as organic fertilizers. Finally, the dissertation reflects on the implications of systemwide nutrient recovery. Nutrient recovery is a shift towards transforming treatment plants to resource recovery plants, in addition to enabling the facilities to reach better cost-effectiveness. Furthermore, nutrient recovery enables decentralized treatment systems should they be desired. To finish the discussion, the true meaning of sustainable technology is discussed.Maailmaanlaajuinen ruoantuotanto nojaa teollisiin lannoitteisiin. Ihmiskunnan räjähdysmäinen kasvu ei olisi ollut mahdollista ilman prosesseja, jotka sitovat typpeä ilmakehästä ammoniakiksi ja maaperästä louhittua fosforikiveä helposti kasveille saatavaan muotoon. Mutta ihmisten lineaariset (kiertävän vastakohta) kulutustottumukset ovat kostautuneet meille. Tuloksena ravinnejärjestelmät, joihin turvaudumme, käyttävät merkittävän määrän energiaa ja luovat joukon ympäristöongelmia. Tämä väitöskirja pyrkii vastaamaan kysymykseen "kuinka voimme sulkea ravinnekierron?". Erillistä huomiota on kiinnitetty siihen, kuinka ravinteiden kiertoa voi hallita kestävästi sekä ympäristön että talouden kannalta. Erilaisissa jätevirroissa on huomattava määrä ravinteita, joita on mahdollista hyödyntää. Naita ravinteita ei kuitenkaan hyödynnetä tehokkaasti, koska se ei ole taloudellisesti kannattavaa tai kiertolannoitteiden (sekä nesteiden että kiinteiden jakeiden) haitta-ainepitoisuudet ovat liian korkeat. Tämä väitöskirja on tehty NPHarvestin ympärille. NPHarvest on ravinteiden talteenottoteknologia, joka on kehitetty Aalto-yliopistossa. NPHarvest ottaa talteen sekä typen että fosforin nestemaisista jätevirroista. Lopputuotteet ovat puhdas ammoniumsuola sekä kiinteä materiaali, jossa on fosforia, kalkkia ja hiiltä. Tuloksien pohjalta on selvää, että NPHarvest on taloudellisesti kilpailukykyinen teknologia. Talteenottoprosessin uutuus on siinä, että se on suunniteltu sietämään jätevesien korkeaa kiintoainepitoisuutta kuluttamatta suurta määrää energiaa. Tämä pitää prosessin operaatiokulut matalina. NPHarvestin elinkaarianalyysin mukaan prosessi on ympäristön tilaa parantava tai neutraali useimmissa vaikutuskategorioissa. Ilmastonmuutoksen suhteen NPHarvestilla on potentiaali olla positiivinen (hiilinegatiivinen). Lisaksi tämä väitöskirja tarkastelee fosforin talteenottoa kemiallisesti saostetusta lietteestä. Talteenotto siitä materiaalista on tekniseltä kannalta mahdollista, mutta tällä hetkellä se ei ole tarpeeksi kannattavaa suuren mittakaavan sovellusta varten. Jätepohjaiset biomateriaalit osoittautuivat sopivaksi keinoksi ottaa fosfori talteen sen jälkeen, kun se oli liuotettu hapolla irti liitteestä. Fosforilla ladattu biomateriaali voi toimia orgaanisena lannoitteena. Lopuksi tämä väitöskirja pohdiskelee ravinteiden talteenoton vaikutuksia laajempaan kokonaisuuteen. Ravinteiden talteenotto edustaa siirtymää kohti resurssien talteenottolaitoksia, en lisäksi että se mahdollistaa naiden laitosten toiminnan kustannustehokkaammin. Lisäksi ravinteiden talteenotto mahdollistaa hajautetut käsittelyratkaisut, mikäli siihen suuntaan on tarpeellista mennä. Pohdiskelun lopuksi mietin, mitä tarkoittaa kestävä teknologia

Membrane contactor onsite piloting for nutrient recovery from mesophilic digester reject water : The effect of process conditions and pre-treatment options

Funding Information: This study is part of the NPHarvest project, which was supported by the Ministry of Environment of Finland , RAKI2 project VN/2250/2019 and Maa- ja vesitekniikan tuki r.y. (MVTT). Publisher Copyright: © 2022 The Author(s)Nutrient recovery is an important segment of the circular economy, and it significantly contributes to sustainable development goals. This work reports on the outcomes of a field testing pilot-scale membrane contactor system designed for nitrogen (N) and phosphorous (P) recovery in the form of high purity ammonium salts and high-quality P containing sludge. The pilot testing was conducted at the Viikinmäki WWTP using digester reject water under different treatment conditions. Our system showed a high tolerance for solids (concentration > 500 mg/L). Field test trials showed that the higher the feed flow, the better the ammonia transfer rate. Decreasing the retention time from 4 h to 2 h increased the ammonia mass transfer rate constant by >150 %. Among the tested feed pH levels, a pH of 10 had the highest solids removal, which in turn resulted in the highest ammonia recovery percentage. A high acid concentration lowered the ammonia transfer rate. Strong acids such as HNO3 and H2SO4 had a higher ammonia recovery than that of H3PO4. Pre-treating feedwater with starch resulted in the same ammonia accumulation rate as a poly-aluminum chloride (PAX)/polymer pre-treatment. The highest PO4−3 removal of 99 % was achieved with a PAX/polymer treatment at pH 10, whereas the highest total phosphorous removal of 77 % was achieved with a starch treatment. The produced sludge consists mainly of CaCO3 emanating from the used lime, which can be used as a soil amendment. The produced ammonium salts were of high purity and have a nutrient content comparable to that of commercial fertilizers. This study provides important insights into the selection of process parameters of membrane contactor systems based on the goal of the treatment, whether it be nutrient removal or recovery.Peer reviewe

Newly developed membrane contactor-based N and P recovery process: pilot-scale field experiments and cost analysis

In this study, a newly developed nitrogen (N) and phosphorus (P) recovery process using a membrane contactor termed NPHarvest was tested with different liquid waste streams in large-scale trials. Ammonia was captured in ammonium sulfate form using a hydrophobic membrane, while phosphorus was precipitated as sludge using alkali precipitation and coagulation processes. The tested streams were selected to cover the potential liquid waste streams for nitrogen recovery and included two different mesophilic digester reject waters, landfill leachate, and separately collected urine. The NPHarvest pilot was tested with hydraulic loads in the range of 12–133 L/h. Nitrogen recovery efficiency reached a maximum of 92.5% with the reject water of mesophilic digester and a maximum ammonia flux of 481.1 mg/L.h was obtained with a urine stream. A mass transfer coefficient was calculated for the four tested wastewater streams using two different approaches, resulting in two value ranges in the order of 10-3 and 10-7 m/s. It was found that the mass transfer coefficient decreased with increase in the initial nitrogen concentration. The recovery of phosphorus varied between 79% and 97%. The quality of ammonium sulfate was evaluated by employing comprehensive tests that included vegetative cells and coliphages, harmful metals, and organic micropollutant measurements. These measurements confirmed that ammonium sulfate meets the Finnish legislation requirements for agricultural use. The use of a diluted acid wash was proven to be sufficient for maintaining membrane surface properties and was confirmed by the observed insignificant loss of hydrophobicity and the mild development of fouling. Finally, the competitiveness of NPHarvest compared to existing processes was confirmed through a detailed cost analysis.Peer reviewe

Nitrogen Recovery from Landfill Leachate Using Lab- and Pilot-Scale Membrane Contactors : Research into Fouling Development and Membrane Characterization Effects

Funding Information: This research received funding from Ministry of the Environment in Finland RAKI2 project VN/2250/2019 and from Maa- ja vesitekniikan tuki r.y. (MVTT). Funding Information: This work was supported by Maa- ja Vesitekniikan tuki r.y. (MVTT). The authors are grateful to Aino Peltola for her assistance with the laboratory analyses. The authors are thankful to Antti Louhio’s help with designing the lab reactors. The authors would also like to acknowledge the support from Onni Lehtikuja with conducting laboratory tests. Publisher Copyright: © 2022 by the authors.Membrane contactor technology affords great opportunities for nitrogen recovery from waste streams. This study presents a performance comparison between lab- and pilot-scale membrane contactors using landfill leachate samples. Polypropylene (PP) and polytetrafluoroethylene (PTFE) fibers in different dimensions were compared in terms of ammonia (NH3) recovery on a lab scale using a synthetic ammonium solution. The effect of pre-treating the leachate with tannin coagulation on nitrogen recovery was also evaluated. An ammonia transfer on the lab and pilot scale was scrutinized using landfill leachate as a feed solution. It was found that PTFE fibers performed better than PP fibers. Among PTFE fibers, the most porous one (denoted as M1) had the highest NH3 flux of 19.2 g/m2.h. Tannin pre-treatment reduced fouling and increased NH3, which in turn improved nitrogen recovery. The mass transfer coefficient of the lab-scale reactor was more than double that of the pilot reactor (1.80 × 10−7 m/s vs. 4.45 × 10−7 m/s). This was likely attributed to the difference in reactor design. An analysis of the membrane surface showed that the landfill leachate caused a combination of inorganic and organic fouling. Cleaning with UV and 0.01 M H2O2 was capable of removing the fouling completely and restoring the membrane characteristics.Peer reviewe

Adsorptive behavior of phosphorus onto recycled waste biosolids after being acid leached from wastewater sludge

Funding Information: This work was supported by Maa- ja Vesitekniikan tuki ry (MVTT) with 48 000 €. MVTT is a Finnish funding organization dedicated to support research and inventions in the field of water and environmental technology. They also support projects that relate to soil protection, agricultural planning and construction. Publisher Copyright: © 2022A vast amount of phosphorus is being wasted or inefficiently utilized in wastewater treatment sludge worldwide. This paper investigates the adsorptive loading of phosphorus from the sludge on different biosolid materials for potential recovery and after use. The phosphorus was leached with acid from wastewater sludge from a chemical P removal process and adsorbed onto four different waste-based biosolid materials. The four biosolids were biochar, commercial lignin, sludge char (pyrolyzed wastewater treatment sludge), and humus (extracted from black liquor). Among the studied biosolids, loaded sludgechar had the highest phosphorus content, yet all materials performed well in P-adsorption. Optimal leaching and adsorption conditions were identified as pH 3 and adsorbent dosage between 0.5 g/L and 0.61 g/L for all biomaterials. The highest adsorption capacity value reached 400–500 mg/g with temperature-dependence. Biosolid materials were characterized with FT-IR, SEM-EDS, XRF, XRD, and XPS. Mathematical modeling through kinetic adsorption models showed that all biomaterials obey a pseudo first order kinetic model, and pore and intra-particle diffusion contribute to the adsorption mechanisms. The isotherm models suggest that the adsorbents are heterogeneous, and the adsorbate physiochemically bond with the functional groups of adsorbents with different adsorptive energies. The process is temperature-dependent and endothermic. XPS and XRD analyses showed that phosphorus adsorbed on the materials is mostly phosphate bound with Fe and Ca. Overall recovery efficiency was 21% (P bound on biosolids / P in sludge before leaching). Such phosphorus-loaded biomaterials are promising for use as feasible slow-release fertilizers.Peer reviewe

Incorporation of main line impact into life cycle assessment of nutrient recovery from reject water using novel membrane contactor technology

Wastewater treatment plant (WWTP) nutrient recovery has recently gained traction in the search for new pathways for fertilizer production. In particular, concentrated waste streams such as reject water from sludge digestion are suitable. The environmental impact of a novel nutrient recovery technology using a membrane contactor (NPHarvest) was examined with an environmental life cycle assessment (LCA). Impact hotspots were benchmarked against a comparable technology (struvite precipitation and ammonia stripping), and the impacts of the two technologies were found to be similar for most studied environmental impact categories. To allow for the inclusion of effects on other parts of the WWTP while limiting the general system boundaries to the reject water treatment, a novel approach to capture the main line impact was developed. The effects on the main line contributed substantially to the overall results. The overall results indicated clear nutrient recovery benefits related to substituted materials in mineral fertilizer production. Additionally, reject water nutrient recovery provided even greater benefits due to reduced N2O emissions and the reduced use of precipitation chemicals in the WWTP main line. Nonetheless, both nutrient removal and recovery were necessary for the two technologies to reach a net zero climate impact in their current pilot scales. Further development of the NPHarvest technology—such as mitigating NH3 emissions, exploring alternative input chemicals and optimizing energy consumption (especially for crystallizing the ammonium salt solution that is produced)—is recommended before full-scale implementation