## 3 Results and Discussion
### Process Water (PW)--Ecotoxicity and Characterization
\begin{table}
\begin{tabular}{c c c c c} \hline
**Process** & **Retention Time** & **Peak Area (\%)** & **Compound** & **CAS Number** \\
**Water** & **(min.)** & **Peak Area (\%)** & **Compound** & **CAS Number** \\ \hline \multirow{4}{*}{PW-180} & 3.722 & 12.00 & Isobutyl acetate & 000110-19-0 \\  & 5.188 & 87.99 & Furfural & 000098-01-1 \\  & 6.120 & 2.32 & Furfural & 000098-01-1 \\  & 26.810 & 1.33 & Cyclohexasiloxane, dodecamethyl- & 000540-97-6 \\ \hline \multirow{4}{*}{PW-215} & 3.657 & 4.15 & Isobutyl acetate & 000110-19-0 \\  & 5.135 & 5.60 & Furfural & 000098-01-1 \\  & 7.574 & 0.93 & 2-Cyclopenten-1-one, 2-methyl- & 001120-73-6 \\  & 7.806 & 1.05 & Ethanone, 1-(2-furanyl)- & 001192-62-7 \\  & 10.049 & 2.33 & 2-Furancarboxaldehyde, 5-methyl- & 000620-02-0 \\  & 12.661 & 7.74 & 1,2-Cyclopentanedione, 3-methyl- & 000765-70-8 \\  & 15.510 & 14.07 & Phenol, 2-methoxy- & 000090-05-1 \\  & 17.071 & 3.05 & 2-Cyclopenten-1-one, 3-ethyl-2-hydroxy- & 021835-01-8 \\  & 24.371 & 3.54 & (Z)-4-Methyl-5-(2-oxopropylidene)-5H- & 026474-45-3 \\  & 27.564 & 7.93 & Phenol, 2,6-dimethoxy- & 000091-10-1 \\  & 29.885 & 3.02 & Vanillin & 000121-33-5 \\  & 35.049 & 5.98 & Homovanillyl alcohol & 002380-78-1 \\ \hline \multirow{4}{*}{PW-250} & 3.716 & 1.50 & Isobutyl acetate & 000110-19-0 \\  & 5.028 & 0.42 & Pyrazine, methyl- & 000109-08-0 \\  & 5.223 & 1.21 & 2-Cyclopenten-1-one & 000930-30-3 \\  & 7.580 & 4.67 & 2-Cyclopenten-1-one, 2-methyl- & 001120-73-6 \\  & 10.144 & 1.26 & 2-Cyclopenten-1-one, 3-methyl- & 002758-18-1 \\  & 10.981 & 1.27 & Phenol & 000108-95-2 \\  & 11.467 & 1.99 & 2-Cyclopenten-1-one, 2,3-dimethyl- & 01121-05-7 \\  & 12.773 & 6.22 & 1,2-Cyclopentanedione, 3-methyl- & 000765-70-8 \\  & 13.248 & 1.39 & 2-Cyclopenten-1-one, 2,3-dimethyl- & 001121-05-7 \\  & 15.551 & 21.46 & Phenol, 2-methoxy- & 000090-05-1 \\  & 20.240 & 0.42 & Furan, 2,5-dihydro-2,5-dimethyl- & 059242-27-2 \\  & 20.560 & 0.80 & Creosol & 000093-51-6 \\  & 21.724 & 5.04 & Catechol & 000120-80-9 \\  & 23.890 & 1.86 & 1,2-Benzenediol, 3-methoxy- & 000934-00-9 \\  & 24.478 & 3.57 & Phenol, 4-ethyl-2-methoxy- & 002785-89-9 \\  & 26.804 & 1.31 & Cyclohexasiloxane, dodecamethyl- & 000540-97-6 \\  & 27.712 & 8.91 & Phenol, 2,6-dimethoxy- & 000091-10-1 \\  & 30.223 & 1.10 & 4-Hydroxy-2-methoxy- & 018278-34-7 \\  & 33.434 & 0.55 & 5-Hepet-3-yn-2-ol, & 063922-41-8 \\  & 33.933 & 0.51 & Cycloheptasiloxane, tetradecamethyl- & 000107-50-6 \\  & 35.102 & 3.86 & Homovanillyl alcohol & 002380-78-1 \\  & 39.589 & 1.12 & Homovanillic acid & 000306-08-1 \\  & 39.725 & 2.30 & Homovanillic acid & 000306-08-1 \\ \hline \end{tabular}
\end{table} 
Table 8: Compounds identified by GC–MS in the process water (PW-180, PW-215, and PW-250) from co-hydrothermal carbonization (Co-HTC) of sawdust and non-dewatered sewage sludge. treatments, such as Co-HTC, the acetyl groups on the hemicellulose chains are cleaved and form acetic acid in the solution. Depending on the process conditions (e.g., temperature), cellulose, hemicellulose, and lignin can undergo partial or complete degradation. The more severe the hydrothermal treatment, the more degradation products are generated, as confirmed by PW compositions in Table 6. For instance, the degradation of cellulose and hemicellulose monomers forms hydroxymethylfurral and furfural, while the lignin degradation produces phenolic compounds [68; 69; 70]. These molecules are intermediates in hydrochloric formation [3]. Therefore, the increase in Co-HTC temperature favors the decomposition of organic biomass and catalyzes the formation of various other chemical substances that may be toxic [21; 71]. Thus, PW became progressively more heterogeneous and toxic as the temperature rose. Although no data were found in the literature regarding the toxicity of PW generated from Co-HTC of sawdust and sewage sludge, similar results were observed in a study exposing _D. magna_ to dilutions of PW produced from Co-HTC of sewage sludge and whey at different temperatures.