Nanostructured but micro‐sized biocatalysts were created by bottom‐up technology using multi‐functionalized silica nanoparticles (NPs) as nano‐sized building blocks to form cross‐linked enzyme‐adhered nanoparticles (CLEANs) as robust micro‐sized particles with beneficial internal structure and good mechanical properties. Systematic surface modification of NPs with a grafting mixture consisting of organosilanes with reactive (aminopropyl) and inert (e. g., vinyl, propyl, phenyl, or octyl) functions resulted in functional NPs enabling cross‐linking agents, such as glutardialdehyde or bisepoxides (glycerol diglycidyl ether, neopentylglycol diglycidyl ether, and poly(propylene glycol) diglycidyl ether), to bind and cross‐link enzymes covalently and to form macroporous microparticles. These CLEANs were able to diminish several weaknesses of traditional cross‐linked enzyme aggregates as biocatalysts, such as poor mechanical resistance, difficult recovery, and storage, strengthening their use for packed‐bed enzyme reactors. Lipase B from Candida antarctica (CaLB) was selected as model enzyme for development of robust CLEANs, which were successfully tested for various industrially relevant applications including a kinetic resolution of a racemic alcohol and the production of various natural fragrance compounds under continuous‐flow conditions.

Through specific chemical and microbiological determinations, the interaction of the extremely low-frequency (ELF) electric field (EF) of 49.9 Hz and 99.9 Hz with the living matter of the activated sludge from a wastewater treatment plant was studied. The determinations showed that a 49.9 Hz EF significantly stimulates both the multiplication of microorganisms (more than 2x, compared to the reference) and the rate of pollutant metabolism, as opposed to a 99.9 Hz EF, where the stimulation of the multiplication of microorganisms is insignificant (below 1.1x, compared to the reference), instead, more strongly stimulates the metabolism of pollutants.

The results of a pilot-scale study on the influence of electric field use for stimulating the active sludge in the biological purification tank of a small capacity wastewater treatment plant (up to 600 m³/day) are presented. Through specific comparative chemical tests (DO, COD, N-NH₄, and Pt) it was found that, by applying a sinusoidal electric field of 5 Vrms/m at 49.9 Hz on the active sludge suspension, the overall pollutant denitrification process speed is doubled compared with the reference case when no stimulation is used. Also, under identical operating conditions, the residual pollutant content of the biological treatment tank outlet water is reduced approximately three times for COD and approximately two times for N-NH₄ and P_t compared to the reference tank. These findings lead to the conclusion that, by stimulating the active sludge microbial activity of the wastewater treatment plants by a sinusoidal electric field of 5 Vrms/m at 49.9 Hz, the time of the biological purification treatment can be reduced by approx. 50%. This leads to a corresponding decrease in energy consumption, which usually represents more than 30% of a wastewater treatment plant’s specific electricity consumption.

In 2020, the energy consumption and volumes of treated wastewater in four village wastewater treatment plants WTP (with a capacity below 10,000 m ³ /month), were monitored monthly. The acquired data showed that the specific energy consumption at the investigated WTP (depending on the period and location) was between 1.561 and 2.580 kWh/m ³ treated wastewater, the annual averages being between 1.786 and 2.334 kWh/m ³ (depending on WTP). Moreover, the consumption given by the equipment related to the biological treatment lines BgT primarily determines the total energy consumption in the WTP-the average annual values of the BgT share in the total energy consumption of the investigated WTP were between 0.632 and 0.729. These findings conclude that the WTP energy efficiency improvement is possible primarily by streamlining aerobic and anaerobic biological treatments.

In this paper, a system to stimulate in extremely low frequency (ELF) electric field the microbiological activity of the microbial flora in the active sludge of a wastewater treatment plant is presented. The designed and realized system was tested in industrial environment with and without ELF electric field stimulation. By comparing the two cases for the same degree of pollutants elimination from the wastewater, it resulted that the ELF electric field application significantly reduces the processing times in the biological treatment stages (to approximately half). Thus, the energy consumption in the biological treatment stage is reduced by approx. 50%, representing approx. 30% of the wastewater treatment plant energy consumption.