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@INPROCEEDINGS{ReineckeLevi:917391,
      author       = {Reinecke-Levi, Diana and Klose, Holger},
      title        = {{S}ystematic case-study: {N}utrient cycling from wastewater
                      to crop via {A}lgal {T}urf {S}crubber ({ATS})},
      reportid     = {FZJ-2023-00605},
      year         = {2022},
      abstract     = {Often, small-scale agriculture and industries in remote
                      areas lack the access to cost-effective wastewater (WW)
                      treatment. One techno-economical solution could be WW
                      treatment by algal biofilm in Algal Turf Scrubbers (ATS).
                      Yet, systematic studies, to the efficiency of ATS biofilms
                      in nutrient-recovery from WWs and -release to crops, are
                      limited. Here we present the findings of a case study to 4
                      pilot-scale ATS operated with 4 WW-types under field
                      conditions for 12 months. We will show results to nutrient
                      transfers, biomass yields, and WW remediation. Further, we
                      will evaluate bioavailability and valorisation of ATS
                      biofilm as slow-release fertiliser or soil
                      improver.INTRODUCTIONIn 2014, the EU declared phosphorous
                      (P) as an essential resource with significant risk to
                      supply, due to its indispensable role as nutrient and its
                      finite deposits in politically instable regions. Yet,
                      excessive application and limited remediation practices
                      caused a chronic loss of phosphorus into the environment.
                      Together with other nutrients, this led to increasing
                      eutrophication of natural water bodies, deterioration of
                      soils, greenhouse gas emissions and public health risks. The
                      recovery of P and closing of nutrient cycles has become
                      vital. And the integration of wastewater remediation and its
                      products in a circular bioeconomy can promote new
                      economically viable technologies. Nutrient cycling by micro-
                      and macroalgae has been successfully demonstrated and could
                      be an environmentally and economically sustainable
                      technology (Siebers, 2019; Solovchenko, 2016; Zou, 2021).
                      The algae are grown in nutrient-rich wastewater, harvested,
                      and processed to feed, fertiliser, or feedstock for further
                      extractions, while the water is cleaned and oxidised. Algal
                      biofilm systems, such as the Algal Turf Scrubbers, can be
                      more cost effective than suspended cultures, due to higher
                      biomass density and easier harvest. Here, we present the
                      first results of a systematic study to the techno-economic
                      challenges and the WW remediation capacity of ATS under
                      field conditions. Materials $\&$ MethodsFour identical
                      pilot-scale Algal Turf Scrubber (ATS) were set up (8 m²)
                      with tipping bucket (30 L), medium tank (1 m³), pump (30 L
                      min-1) and IoT sensors (aquatic, environmental). The ATS
                      were operated at a farm and a WWTP with municipal WW,
                      biogas-effluent, pig and cattle manure, respectively. The
                      ATS with mWW was operated in constant mode. The ATS with
                      biogas-effluent, pig and cattle manure received weekly fresh
                      WW (1 m³). All ATS were inoculated with a pre-existing
                      biofilm. ATS biofilms were harvested and analysed weekly
                      (Jul-Oct) or biweekly (Nov-Apr), respectively. Initial
                      characterisation of the 4 WWs was done by a certified
                      external lab. Total phosphorous (TP) and total nitrogen (TN)
                      concentrations were measured at start (d0) and end (d7) of
                      each batch, respectively. Wet and dry weight (DW), ash-, N-,
                      and P-content, and elemental composition of the biofilm were
                      determined at harvest (d7). Population assembly and shifts
                      were monitored microscopically and documented throughout the
                      year. Selected biofilms were analysed for nutrient
                      composition, heavy metals, Chrome (VI), Perfluorate Tenside
                      (PFT), Salmonella sp., E. coli, Enterobacteria, and
                      antibiotics. ResultsThe installation and inoculation of the
                      four ATS-systems were completed in spring 2021. The inoculum
                      derived from an established ATS and was supplemented with a
                      local sample of algal biofilm from the WWTP. Microscopic
                      observation revealed a mesocosm-like assembly of bacteria,
                      pro- and eukaryotic algae, fungi, and protozoa in an
                      extracellular polymeric substance (EPS), Fig. 1. After six
                      weeks, the biofilms covered the complete substrate (8 m²)
                      and pre-cultivation with standard medium was transitioned to
                      the individual WWs, Fig. 1. Then biofilm populations shifted
                      from filamentous cyanobacteria and green algae (Chlorophyta)
                      towards unicellular Diatoms (Bacillariophyta) and green
                      algae. All ATS maintained as a stable batch-culture with
                      weekly harvest cycles from July to October, despite harsh
                      weather events. Operational conditions, such as flow rate,
                      WW admixture and sensor mounting, were adjusted to the
                      specific location and WW type, but maintained a comparable
                      setting. Due to the high content of total suspended solids,
                      concentrations were adjusted to $1\%$ (v/v) for unfiltered
                      biogas-effluent, pig and cattle manure, respectively. In
                      contrast, municipal WW was directly pumped from a secondary
                      sedimentation basin onto the ATS and discharged into a
                      polishing pond. In a representative batch, $47\%$ of total
                      nitrogen (NH4+ 0.6; NO2- 0.1; NO3- 0.6 mg L-1) were
                      recovered from the mWW in a single flow-through, Fig. 1. In
                      7 days, the ATS yielded a biomass and productivity of 238 g
                      DW and 4.2 g m-2 d-1, respectively, Fig. 1. ATS with pig-,
                      cattle- and biogas-effluent medium yielded comparable
                      biomasses of ~223, 240, and 286 g DW, respectively, Fig. 1.
                      However, the ash-content varied significantly between the
                      mWW $(43.2\%),$ pig $(31.9\%),$ cattle $(46.4\%)$ and biogas
                      $(36.7\%)$ medium, due to the varying share of diatoms in
                      the individual biofilms, Fig. 1. Likewise, the elemental
                      composition and N:P:K ratio of the biomasses varied for the
                      WWs. Biomass in PM gained the highest carbon content and
                      N:P:K ratio of $36\%$ and 10:5:1, respectively, Fig. 1.
                      These biomasses were processed for long-term fertiliser
                      experiments with ryegrass, Fig. 1. Preliminary results
                      showed comparable crop performance and yields for mineral
                      and ATS-biofilm fertiliser, respectively (Siebers, 2019).
                      Detailed results to the nutrient transfer from WW to ATS
                      biofilm to crop, as well as to potential human and
                      environment risks will be provided.},
      month         = {Nov},
      date          = {2022-11-10},
      organization  = {Zukunftslandwirtschaft - Innovative
                       Entwicklungen, Köln-Auweiler
                       (Germany), 10 Nov 2022 - 10 Nov 2022},
      subtyp        = {Invited},
      cin          = {IBG-2},
      cid          = {I:(DE-Juel1)IBG-2-20101118},
      pnm          = {2171 - Biological and environmental resources for
                      sustainable use (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2171},
      typ          = {PUB:(DE-HGF)31},
      url          = {https://juser.fz-juelich.de/record/917391},
}