## 4 Discussion  
The issue of the mechanisms of MW inactivation of microorganisms and contribution of \"non-thermal effects\" was widely discussed and reviewed by [PERSON] and [PERSON] [10]. The application of MW at a sub-lethal temperature of 40 \({}^{\circ}\)C on _E. coli_ for a duration of 1 min resulted in disruption of the permeability barrier, i.e., cell leakage and entry of large molecules, such as labeled dextran, into the cell were observed [27]. They noted that 10 min after terminating the MW radiation, the cell morphology reverted to that before the treatment, i.e., the MW treatment was not biocidal. It can be stated, however, that prolonged disruption of the permeability barrier at any temperature would lead to cell death. In the current work (Section 3.5) about five-fold less energy was required for \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Source of sample** & **9 L** & **31 L** & **44 L** \\ \hline TAP & 5 & 690 \({}^{\text{c}}\) & 50 \({}^{\text{d}}\) \\ Container & 7 & 200 \({}^{\text{c}}\) & 140 \({}^{\text{d}}\) \\ M1-MW & \(<\)1 & 1100 \({}^{\text{c}}\) & 250 \({}^{\text{c}}\) \\ M2-HCl & \(<\)1 & 23 & 71,000 \({}^{\text{b}}\) \\ M3-MW & 13 & 980 \({}^{\text{c}}\) & 180 \({}^{\text{c}}\) \\ M4-HCl & 11,000 \({}^{\text{b}}\) & 260 \({}^{\text{c}}\) & 550,000 \({}^{\text{a}}\) \\ H1-MW & 8 & 11,000 \({}^{\text{b}}\) & 8,200 \({}^{\text{b}}\) \\ H2-HCl & \(<\)1 & 550,000 \({}^{\text{a}}\) & 250,000 \({}^{\text{a}}\) \\ H3-MW & 1 & 260\({}^{\text{c}}\) & 60 \({}^{\text{d}}\) \\ \hline \hline \end{tabular} \({}^{*}\) The experiment was completed by October 15, 2019. Columns 2–4 in the table indicate the filtered volumes. The notation describes the history of treatment, e.g., M2-HCl indicates that this sample was obtained from a column which underwent a first regeneration by MW heating and a second regeneration by washing with a dilute HCl solution. The estimated relative errors in the number of bacteria in cases \({}^{\text{a}\text{b}\text{c}\text{d}}\), are 80%, 50%, 30%, and 20%, respectively; in other cases, they are less than 10%.  
\end{table} 
Table 6: Comparison of removal efficiency of TBC by ODTMA granules after the second regeneration (CFU per mL): number of emerging bacteria after passage of given volumes \({}^{*}\). a biocidal or biostatic effect for TBC present in hot water (below boiling point) under MW operation than heating by an electric plate. An evaluation of the maximal number of bacteria that could be retained by 1 g of the complex [5; 8; 9] indicates that the available area of the complex is several orders of magnitude larger than the total area of the external surfaces of bacteria. Hence, the limit on the number of bacteria which can be adsorbed is dictated by the balance between adsorption and desorption processes. For filtration of a single species of bacteria, a model of kinetics of filtration, which considered convection, adsorption, and desorption could simulate and yield predictions for the kinetics of bacteria filtration [5; 6; 8; 9]. In the initial stages of filtration in the current experiments (on a time scale of days in the case of the filters used) only a few bacteria were found to be emerging through the filter, but eventually the pores in the filter included free bacteria, which could reproduce, and the numbers of bacteria emerging through the filter kept increasing with the volume passed and with time. At this stage the regeneration has to inactivate the bacteria residing in the water-filled pores, which in the current filters constitute about 50% of the volume of the active layers. Regeneration can increase the shelf life and capacity of the filter and reduce the frequency of its replacements. In planning the current study, cost evaluations favored an initial step of washing the used filter by 250 mL of a dilute HCl solution (0.05 M) followed by 500 mL of tap water, rather than washing by Na-hypochlorite solution [5; 8].