Reduction of ripening time of full-scale manganese removal filters with manganese oxide-coated media

Abstract

Effective manganese removal by conventional aeration-filtration with virgin filter media requires a long ripening time. The aim of this study was to assess the potential of manganese oxide-coated media to shorten the ripening time of filters with virgin media, under practical conditions. A full scale filter filled with virgin sand and a full scale filter filled with anthracite/sand were operated at two groundwater treatment plants, in parallel with (full scale) test filters, with an additional layer of Manganese Oxide-Coated Sand (MOCS) or Manganese OxideCoated Anthracite (MOCA). Significantly different ripening times were observed to achieve an effective manganese removal: 55 days for a filter with virgin sand and 16 days for a filter with virgin anthracite/sand, respectively. The observed differences could be attributed to different feed water quality, different iron loading, and backwashing intensity and frequency. In batch experiments fresh MOCA and MOCS showed good 2 manganese adsorptive properties. Addition of a shallow layer of fresh MOCA in test filters eliminated the ripening time, while a layer of aged MOCS did not significantly shorten the ripening period. The poor performance of the aged MOCS was likely caused by changed properties of aged and dried MOCS, that had lost its adsorption capacity, the auto-catalytic activity and the biological activity.

Predicting manganese and iron precipitation in drinking water biofilters

“…If the water contains aggressive carbon dioxide, pH could be increased by using calcium carbonate filter media (Cox, 1933). Alternatively, utilities could consider using filter media pre-coated in Mn (oxyhydr)oxides to encourage heterogeneous Mn removal (Bruins et al, 2015b).…”

Mineral Materials Coated with and Consisting of MnOx—Characteristics and Application of Filter Media for Groundwater Treatment: A Review

“…In chemically coated filter media, the carrier dominates quantitatively over the coating and it has been shown that for this type of materials it is better to compare adsorption capacity in terms of unitary value of specific surface area [144]. Bruins et al [145] considered this need when comparing filter media of varying density and proposed a reference to the unitary volume of material. As shown in the data presented in Table 2, the amount of MnO x deposited on a mineral support is varied and most often ranges from a few tenths to several mg/g of coated filter media.…”

“…In the start-up period, the filter slowly achieves higher and higher treatment efficiency until satisfactory results are obtained. The duration of this period varies and depends on many factors, such as chemistry of groundwater, technological conditions of water filtration, filter design, and properties of the filter medium, implies a rate of ripening [31,145]. A summary of information on this topic is provided in Table 5.…”

Start-up of bench-scale biofilters for manganese removal under tropical conditions: a comparative study using virgin pumice, silica sand, and anthracite filter media

“…7 In addition, the manganese oxides (MnO x ), formed by these processes, gradually cover the filter medium, contributing to the removal of Mn through auto-catalytic adsorption and subsequent oxidation of adsorbed Mn by biological and/or physicochemical means. 8,9 At the end of the start-up period, efficient and stable removal of Mn is expected. 10 The length of this period is potentially influenced by the type and amount of manganese oxide coated in the filter medium, 11 the quality of the raw water, and some operational or design aspects such as the volumetric loading of iron, the backwashing strategy, and the type of filter medium.…”

“…10 The length of this period is potentially influenced by the type and amount of manganese oxide coated in the filter medium, 11 the quality of the raw water, and some operational or design aspects such as the volumetric loading of iron, the backwashing strategy, and the type of filter medium. 8,12 The attachment of bacteria to the filter medium is a physicochemical process that can be influenced by the texture, the properties of the surface, the accessible areas of the support medium, 13 and the water temperature. 14 Microbial colonization would increase as the surface roughness of the filter media increases, as shear forces decrease and the surface area increases.…”