Direct capillary nanofiltration was tested for reclamation of tertiary effluent from a municipal wastewater treatment plant. This process can be regarded as a promising treatment alternative for high quality water reuse applications when combined with powdered activated carbon for enhanced removal of organic compounds. The nanofiltration was operated at flux levels between 20 and 25 L/(m2 h) at a transmembrane pressure difference of 2-3 bar for approximately 4,000 operating hours. The study was conducted with PAC doses in the range from 0 to 50 mg/L. The plant removal for DOC ranged from 88-98%. The sulfate retention of the membrane filtration process was between 87 and 96%. The process provided a consistently high permeate quality with respect to organic and inorganic key parameters.

This experimental study investigates the anaerobic digestion of waste water from hydrothermal carbonisation of fine mulch (wood chips) in combination with a co-substrate for the first time. Two anaerobic reactors, an anaerobic filter (AF) and an anaerobic moving bed bioreactor (AnMBBR), were operated over a period of 131 days at mesophilic conditions. The organic loading rate was increased to a maximum of 8.5 g L d in the AF and the AnMBBR. Both reactors achieved similarly efficient chemical oxygen demand removal rates of 80% approximately (approx.) and high methane production rates of approx. 2.7 L L d. Nevertheless, signs of an inhibition were observed during the experiments.

Granular activated carbon (GAC) adsorption, as well as ozonation in combination with biodegradation was investigated in order to remove refractory organics from biologically pre-treated process waters (PW) produced by the hydrothermal carbonization (HTC) of spent grains and fine mulch. Kinetic tests revealed that the organics in spent grains PW had much lower molecular weights than organics in fine mulch PW. Moreover, isotherms showed that they were more strongly adsorbable. This was confirmed in GAC column experiments, where the breakthrough curves could be predicted fairly well by a dynamic adsorption model. On the other hand, ozonation had a stronger effect on fine mulch PW with respect to an enhancement of the aerobic degradability. Thus, the type of input material determines the properties of soluble reaction products from the carbonization process that must be accounted for when selecting the most suitable post-treatment method for HTC PW. However, adsorption on granular activated carbon should always be the final stage.

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