What is the ruling on washing a board on which Quranic verses are written if the ritually impure water will go into the sewage system?

Muslims have unanimously agreed on the obligation to respect the word of Allah, and that insulting the Qur’an and treating it with disdain constitutes apostasy. Among the ways of insulting it is placing filth upon it or leaving it in filth when it is possible to rescue it. Therefore, washing the words of the Qur’an into sewage drains is one of the greatest abominations, and the perpetrator must repent immediately.