Hi Guys,
I'm working as process engineer on the design of a set of manganese rapid gravity filters at an existing WTW with upstream DAF & RGFs. I've been tasked with confirming likely headloss through these secondary filters so we can confirm hydraulics. The primary filtered water will be dosed with hypo & lime to ensure oxidation & precipitation of the manganese on to the secondary filters.
Twort’s Water Supply(5th ed., 2002) states that “in the downflow filter design with upflow washing, it is usual for the filter to operate with about 1.5 – 2m of water over the bed”. “The head loss in a clean filter is made up of clean media and underdrain losses which is usually less than 0.25m. Therefore when a filter is returned to service after washing, the loss of head through the bed and underdrain should be less than 0.3m. The rate of head loss development is a function of solids retention capacity of the filter and is lower for coarse sand filters than for graded sand filters....The head loss allowed for retention of suspended solids (clogging head) is usually in the range of 1.5 – 1.8m. Therefore, filters are allowed to run to 1.8 -2m head loss.”
From the above, it would appear that the dirty headloss is approx 1.2 – 1.5m in primary RGFs. Obviously, solids retention on secondary filters will be less but does anyone have a reference or estimation for headloss through secondary manganese removal RGFs?
Thanks in advance.
James
I'm working as process engineer on the design of a set of manganese rapid gravity filters at an existing WTW with upstream DAF & RGFs. I've been tasked with confirming likely headloss through these secondary filters so we can confirm hydraulics. The primary filtered water will be dosed with hypo & lime to ensure oxidation & precipitation of the manganese on to the secondary filters.
Twort’s Water Supply(5th ed., 2002) states that “in the downflow filter design with upflow washing, it is usual for the filter to operate with about 1.5 – 2m of water over the bed”. “The head loss in a clean filter is made up of clean media and underdrain losses which is usually less than 0.25m. Therefore when a filter is returned to service after washing, the loss of head through the bed and underdrain should be less than 0.3m. The rate of head loss development is a function of solids retention capacity of the filter and is lower for coarse sand filters than for graded sand filters....The head loss allowed for retention of suspended solids (clogging head) is usually in the range of 1.5 – 1.8m. Therefore, filters are allowed to run to 1.8 -2m head loss.”
From the above, it would appear that the dirty headloss is approx 1.2 – 1.5m in primary RGFs. Obviously, solids retention on secondary filters will be less but does anyone have a reference or estimation for headloss through secondary manganese removal RGFs?
Thanks in advance.
James
