activated alumina, pseudoboehmite, Zibo XiangRun Environment Engineering Co., Ltd.

Performance of each media was assessed by taking daily samples of the feed and treated waters primarily for arsenic analysis, from which the capacity of the media for arsenic could be calculated.

Media investigated included:

?activated alumina of two grain sizes (14/28 and 28/48),

?a granular ferric hydroxide media (Wasserchemie GEH),

?catalytic manganese media,

?strong base anion exchange resins (including Purolite A400).

The ion exchange resin and the catalytic media showed a very low capacity for arsenic, treating less than 1,000 bed volumes (BV) to 10μg/l in the treated water. Furthermore, arsenic was displaced from the resin to much higher concentrations than in the feed water (over 50 μg/l), making it particularly unsuitable for this application. Performance of the activated alumina and GEH media are reviewed below.

Alumina results

Performance at each EBCT is shown in Table. 1, indicating an increasing arsenic capacity with increasing EBCT. This means that, for a given site, higher costs for larger plant to achieve longer EBCT would be offset to some extent by a lower operating cost for replacement (or regeneration) of exhausted media. Performance of activated alumina (14/28 grade) was evaluated at four pH levels, achieved by dosing acid to the feed to three columns to reduce the pH relative to that of the feed water. The results, shown in Fig. 1, demonstrate that reducing the pH gave a dramatic increase in capacity. The bed life at the unadjusted pH was around 20 days compared with over 200 days at pH 6.