# Recent Advances in Hydrothermal Oxidation Technology for Sludge Treatment
## 2 Results and Discussion
### Research on Influencing Factors of Sludge Treatment by HTO
\begin{table}
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**Sludge Type** & **Treatment Process** & **Optimal Time** & **Effect of Time (t) Change** & **Change Efficiency/Yield (mg/L)** & **Reference** \\ \hline \multirow{4}{*}{Urban Sludge} & & & t increases, the yield of SCOD decreases first and then stabilizes, and the concentrations of NH\({}_{3}\)-N and NO\({}_{3}\)-N decreases slowly with the extension of reaction time & \multirow{4}{*}{[11]} \\  & & & t increases, the concentration of & (t: 0–60 min, 180 \({}^{\circ}\)C) \\  & & & & tCOT: \\  & & & removal rate of carbohydrates, TOC, and protein concentration first increases and then decreases (not significant) & 1500–2750-2000; NH\({}_{3}\)-N: 200–600 \\ \hline \multirow{4}{*}{Urban Sludge} & & & t increases, the removal rate of COD increases gradually, while the removal rate of VSS does not change much & \multirow{4}{*}{[29]} \\  & & & t increases, the removal rate of COD increases gradually, while the removal rate of VSS does not change much & & \\  & & & t increases, the removal rate of COD increases gradually, while the removal rate of VSS does not change much & & \\  & & & t increases, the removal rate of COD increases at the same time, and the increase in removal rate is linear with the reaction time, but there is a node value & & \\  & & & t increases, the removal rate of COD increases gradually, while the removal rate of VSS does not change much & & \\  & & & t increases, the removal rate of COD increases gradually, and VSS increases with the increase in temperature, and the removal rate of VSS (which is very high in a short time) is much higher than that of COD & & \\  & & & t increases, the removal rate of COD increases with the increase in temperature, and the removal rate of VSS (which is very high in a short time) is much higher than that of COD & & \\  & & & t increases, the removal rate of TCOD increases with the increase in temperature, and the removal rate of VSS is high, and the increase in the removal rate is linear with the reaction time & & \\  & & & t increases, the removal rate of VSS (t: 20–60 min) The removal rate of VSS is changed little compared with the removal rate of COD & & \\  & & & t increases, the removal rate of initial VSS is higher, the removal rate of COD increases gradually with the increase in time & & \\  & & & t increases, the removal rate of VSS is higher, the removal rate of COD increases gradually with the increase in time & & \\  & & & t increases gradually with the increase in time & & \\  & & & t increases, the removal rate of VSS is 85–93.6\% & & \\ \hline \multirow{4}{*}{Olifield Sludge} & & & t increases, the removal rate of VSS and COD increases, and the removal rate of VSS is changed little compared with the removal rate of COD & & \\  & & & t increases, the removal rate of initial VSS is higher, the removal rate of COD increases gradually with the increase in time & & \\  & & & t increases gradually with the increase in time & & \\  & & & t increases, the removal rate of VSS is 85–93.8\% & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Influence of reaction time change on sludge treatment by HTO technology in recent years. rate. Under these conditions, higher oxygen concentrations can provide more reactive oxygen species, facilitating the oxidative decomposition of organic matter and generating various beneficial free radicals, such as hydroxyl radicals, which play a crucial role in removing organic pollutants. The oxygen supply is primarily determined by the initial oxygen pressure. Research on common industrial sludge treatment has shown that, at elevated temperatures, increasing the initial oxygen pressure is beneficial for the removal of organic pollutants. For instance, [PERSON] et al. demonstrated that the additional oxygen supply plays a vital role in the wet oxidation of pharmaceutical sludge, significantly increasing the TCOD removal rate as oxygen levels rise.