Approximately three to eight percent of water treated in conventionally treated potable water filtration facilities can be lost from backwashing the media filters to waste. In the past, backwash wastewater was typically returned to the front of the treatment process and blended with the raw water being treated, or discharged to a surface water under a National Pollution Discharge Elimination System (NPDES) permit (see Figure No. 1). The potential concentration effects for protozoans such as Giardia and Cryptosporidium, and other contaminants from recycling backwash water has raised concern among regulatory agencies and water utilities. Recycling backwash water can increase the concentration of contaminants within the treatment process and thereby increase the risk of protozoans entering the distribution system. Pilot testing membrane filtration to treat the backwash wastewater was conducted at three locations with different water quality and treatment processes using hollow fiber microfiltration membranes. The physical removal capabilities of the membrane process was confirmed by performing a challenge study with Giardia cysts and Cryptosporidium oocysts. During the operation of the membrane pilot system, water quality and operational parameters were monitored to evaluate the performance of the process unit. The most important of these is the ability to provide consistent microbial and particle removals under the operating conditions used. The feasibility of using membrane filtration to recover backwash water was then developed.
| File Size : | 1
file |
| ISBN(s) : | 089867834X |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 01/01/1995 |
