Treatment of chlorinated manganese backwash water 1

[tipp79]

I'm currently working on a project where we are upgrading an existing water treatment works by adding secondary rapid gravity filters for manganese removal. These filters will be backwashed and the backwash discharged to a stream. As part of the proposed discharge consent, we will be required to treat this water to remove Manganese (average 10.4mg/l) and chlorine (avg 1.2 mg/l). The manganese is required to be treated to approx 50-100ug/l. It is proposed to discharge through a filter bag, followed by a GAC cartridge filter. The flowrate has not been decided upon as yet- it will depend on what flowrate is suitable for effective treatment through bag filters and filter cartridges. Basically, 15m3 will need to be discharged over a day so the flow through the bag filter and GAC filter will be in the region of 10l/s if discharged evenly over 24 hours.

Any advise on the feasibility of the above or alternative treatment options appreciated? (N.B. The ground isn't suitable for soakaway, no sewer connection available and there are slow sand filters upstream so no primary backwash water to mix secondary backwash water with- Secondary RGF dirty backwash water tends not to settle well on its own).

Many thanks

J

 

[bimr]

Not sure that a bag filter would work and why the carbon?

You probably should investigate the use of a backwash storage tank with 2 backwash volumes. Then pump the backwash through a clarifier with a thickening section, and then through another filter. Take the thickened sludge through a filter press to dewater it.

The backwash tank should have enough residence time to allow the manganese to be thoroughly oxidized.

 

[hydrusman]

You can also look at discharging the backwash effluent into a gravity, geotextile container allowing the supernatant to exfiltrate out the bottom. Try Flo-trend

http://WWW.FLOTREND.COM

and you can put GAC in the bottom of the unit to give you dechlorination.

 

[aquaseaulutions]

If you are not allowed to discharge any liquid concentrate you will have to use filtration and bag filtration is the cheapest solution I know. Instead of using GAC cartridges, I suggest Carbon block cartridges, they have an higher filtration capacity.

 

[aquaseaulutions]

You may also install a sedimentation tank and pump the supernatant back to filters. Oxidized Mn is easily settleable. And then only purge the sediment to a bag filter.