The problem of malodours from the dewatering and storage of liquid sludge produced by the chemically-enhanced primary treatment (CEPT) process is an urgent problem. Hydrogen sulfide (H₂S) is generated during various stages of processing CEPT liquid sludge, starting from the liquid sludge holding tanks to dewatering centrifuges and dewatered sludge storage silos and transport container. H₂S, NH₃, and VOCs are continuously generated by microbial action during the entire process. Hydrogen sulfide is particularly difficult. It is generated by sulfate-reducing bacteria (SRB) under septic conditions, and is released from the liquid sludge in the holding tanks, during the dewatering process and from the sludge cake stored in silos.

A new approach based on the use of a tetraethyl orthosilicate...[ Read more ]

The problem of malodours from the dewatering and storage of liquid sludge produced by the chemically-enhanced primary treatment (CEPT) process is an urgent problem. Hydrogen sulfide (H₂S) is generated during various stages of processing CEPT liquid sludge, starting from the liquid sludge holding tanks to dewatering centrifuges and dewatered sludge storage silos and transport container. H₂S, NH₃, and VOCs are continuously generated by microbial action during the entire process. Hydrogen sulfide is particularly difficult. It is generated by sulfate-reducing bacteria (SRB) under septic conditions, and is released from the liquid sludge in the holding tanks, during the dewatering process and from the sludge cake stored in silos.

A new approach based on the use of a tetraethyl orthosilicate hydrogel using a controlled and sustained dosing of nitrite at low concentration was successfully implemented to suppress H₂S odour on laboratory-, bench- and large-scale. The hydrogel targets SRB, decreasing both their viability and activity. A gel containing less than seven percent of active ingredients can decrease H₂S emission by more than 90 % at a 0.1 weight percent gel-to-sludge loading.

Further, a continuous process to produce beads of hydrogel has been developed. The continuous production process can produce hydrogel at a higher production rate, while producing it in the form of beads confers the hydrogel with better suspension properties and homogenous size.

Finally, a method to continuously disinfect the flushing water in toilets is proposed, to tackle the emission of bacteria and viruses present in this water as an aerosol from flushing the toilet, contaminating the environment. This method can produce a disinfectant in-situ that is released in a sustained manner and has shown the ability to last for over 30 days with viricidal and bactericidal properties.