Performance of mineralwool as filter medium for the treatment of contaminated drain water in the urban context of Delhi, India

Abstract

Delhi is facing a very rapid urbanization, making it difficult to keep up with the construction of sewerage and water treatment infrastructure. The LOTUSHR project was created to research alternative solutions to treat mixed water streams and prevent pollution flows from urban drains into the environment.

Biofiltration was identified as a suitable on-site sanitation alternative to provide adequate water quality and hygienic conditions. In particular, this work is intended as a first step in the future design of the biofilter, by investigating the potential of hydrophilic mineralwool as a filtering medium for the Barapullah drain contaminated water. Mineralwool performance was tested, focusing on nutrients and heavy metals removal. The effect of different HRT’s on biofilm formation was evaluated and the minimum length for optimal filter performance was researched. The fieldwork was conducted in Delhi between the 4th January and 9th February 2018. Four mineralwool filters were monitored, running with different operational parameters under the same environmental conditions.

Biological activity was identified as a key factor in increasing the removals of COD and NH3-N. Bare mineralwool achieved PO4-P reduction, independently from the presence of a biofilm. Moreover, a shorter HRT determined a selection pressure for attached biomass growth, leading to a more swift biofilm formation. Unfortunately, part of the obtained results showed a high error margin. Possible reasons for these error margins are discussed.

Hydrophilic mineralwool is an emerging material and not much research is yet available on its water filtering properties. This thesis suggests that mineralwool can be used as a pre-treatment step in the sanitation of polluted drains in rapidly urbanizing megacities.