[Mechanism of Removing Iron and Manganese from Drinking Water Using Manganese Ore Sand and Quartz Sand as Filtering Material].

Two lab-scale biofilters packed with manganese ore sand and quartz sand were constructed to reveal the behavior in removing iron and manganese during the start-up period. Meanwhile, the removal mechanism of the two sands was also investigated by means of EDS, XPS, and SEM. With the influent iron (2-3 mg·L-1) and manganese (0.3-0.6 mg·L-1), the start-up operational results indicated that the quartz sand biofilter needed 15 and 30 d to achieve the removal of iron and manganese, respectively. The manganese ore sand only required 10 d to remove iron, while the effluent manganese was always below of 0.1 mg·L-1. The results confirmed that the natural iron and manganese oxides coated on the manganese ore sand surface could explain its better removal behavior as compared to quartz sand. However, the generated iron oxide could also act as the adsorbent and catalyst like natural iron oxide, only when iron removal occurred in the quartz sand biofilter. The final product of iron removal was a complex consisting of divalent and trivalent iron, with a specific value of 1:1.44-1:1.54. Moreover, during the start-up period, manganese ore sand transformed manganese from divalent to trivalent by the catalytic effect, while the latter tended to be converted to the quadrivalent state under the bioactivity. The quartz sand could adsorb manganese but easily became saturated, and then the removal was dominated by bioactivity. The product generated by the manganese removal process was also a complex with the three valences. Moreover, the two complexes could coat onto the surface of the sands, but most of the iron complex was easily washed out of the filtering layer. Conversely, the manganese complex tended to coat onto the manganese ore sand surface or accumulate between the pores of quartz sand.

[Trace Amounts of Phosphorus Removal Based on the in-suit Oxidation Products of Iron or Manganese in a Biofilter].

In order to remove trace amounts of phosphorus from water bodies, a lab-scale biofilter was constructed to investigate the capacity of in situ oxidation products of iron or manganese for phosphorus adsorption. SEM, EDS, BET, and zeta technologies were employed to reveal the adsorption mechanisms. The results indicated that phosphorus could be removed by the oxide products generated from the iron or manganese removal process, at 106.28 µg·mg-1 and 77.98 µg·mg-1, respectively, as shown by the linear relationships between phosphorus removal and the two oxides. SEM, EDS, and BET analysis demonstrated that the BET specific surface areas for the iron- and manganese-rich oxides were 96 m2·g-1 and 67 m2·g-1, respectively, with the former accumulated between the pore spaces of the filtering sand and easily washed out of the layer by backwashing, whereas the latter coated the surface of the filtering sand. Thus, backwashing was favorable for phosphorus adsorption in the iron oxidation process to avoid overaccumulation. Moreover, the zero point of charge of the two oxides indicated electrostatic attraction may have occurred between iron-rich oxide and phosphorus; however, inner-sphere complex reactions obviously occurred for the two oxides because the zero point of charge after phosphorus adsorption decreased to a lower level. In addition, other anions were negatively complexed with the phosphorus on the surface of the oxides, it demonstrated that phosphorus adsorption on the surface of the two oxides seemed to be a specific adsorption.

Effective start-up biofiltration method for Fe, Mn, and ammonia removal and bacterial community analysis.

Three identical lab-scale biofilters were employed to optimize the start-up process for simultaneous removal of iron (Fe), manganese (Mn), and ammonia from potable water supplies. Nitrifying sludge and backwashing sludge containing Mn-oxidizing bacteria (MnOB) were used as the inocula. The start-up strategies consisted of simultaneous and separate inoculation of the two kinds of sludge. The influent Fe was removed immediately when the biofilters began to operate. The effects of nitrification for ammonia removal showed no significant difference between these biofilters. However, the beginning of Mn removal with separate inoculation was faster than that of simultaneous inoculation. The Mn removal can be described by using first order reaction; and the k (rate constant, min(-1)) values were 0.147±0.007 (mean±standard deviation) and 0.153±0.006. Besides the commonly reported MnOB genus Crenothrix, MnOB genera were also found to be related to the genera rarely reported in the potable water treatment systems.

Autotrophic nitrogen removal process in a potable water treatment biofilter that simultaneously removes Mn and NH4(+)-N.

Ammonia (NH4(+)-N) removal pathways were investigated in a potable water treatment biofilter that simultaneously removes manganese (Mn) and NH4(+)-N. The results indicated a significant loss of nitrogen in the biofilter. Both the completely autotrophic nitrogen removal over nitrite (CANON) process and nitrification were more likely to contribute to NH4(+)-N removal. Moreover, the model calculation results demonstrated that the CANON process contributed significantly to the removal of NH4(+)-N. For influent NH4(+)-N levels of 1.030 and 1.749mg/L, the CANON process contribution was about 48.5% and 46.6%, respectively. The most important finding was that anaerobic ammonia oxidation (ANAMMOX) bacteria were detectable in the biofilter. It is interesting that the CANON process was effective even for such low NH4(+)-N concentrations.

Biodiversity and quantification of functional bacteria in completely autotrophic nitrogen-removal over nitrite (CANON) process.

The research was conducted to investigate the microbial diversity and population with the different concentration of NH(4)(+)-N in a biofilm reactor filled with volcanic filter for completely autotrophic nitrogen-removal over nitrite (CANON) process. The reactor had an excellent performance with the decreasing of NH(4)(+)-N concentration from 400 to 200 mg L(-1) while NH(4)(+)-N removal loading reduced at the NH(4)(+)-N concentration of 100 mg L(-1). Biodiversity analysis indicated that Nitrosomonas related aerobic ammonia oxidizing bacteria (AOB) and Planctomycetales-like anaerobic ammonia oxidizing (anammox) bacteria were dominant functional bacteria. Despite the different influent NH(4)(+)-N concentration, anammox bacteria had a low and stable biodiversity, which was not the same to AOB. With the concentration reduction of influent NH(4)(+)-N, the estimates of total bacteria population ranged between 2.29×10(11) and 1.44×10(12) copies mg(-1) total DNA, and the quantity of AOB decreased while anammox bacteria kept stable. The population of Nitrospira increased and little Nitrobacter was detected during the experiment.