This may be the result of CH2O oxidizing to other toxic intermediates
by the UV/H2O2 process as represented by the TOC
residuals of this process in Fig. 5.
For real applications of advanced oxidation processes in
treating formaline wastewater, it is recommended that the combined
Fenton and photo-Fenton process is a viable technique
for formaldehyde and methanol degradation with relatively low
toxicity of the by-products in the effluent.