AWWA MTC57640

As freshwater supply options become fewer and more difficult to access, municipal water suppliers have begunturning to supplies of lesser quality. These supplies include hard, colored, and brackish waters that require advancedtreatment, such as reverse osmosis (RO) and nanofiltration (NF). Groundwater sources have been, overwhelmingly,the sources of choice due to more consistent and predictable water quality. However, more recently, many have beenlooking at treating low quality surface water supplies with RO or NF.Treating surface water with RO and NF poses certain challenges associated with system design and membranefouling. Due to the wide variations seen in surface water temperature, turbidity, and organic carbon concentrations,engineers must be particularly careful when designing surface water RO and NF systems. Adequate pumping design,intake type and location, and pretreatment are paramount to controlling system operation, finished water quality, andtreatment cost.Pilot tests are a useful tool for developing design criteria for surface water RO treatment processes. However,appropriate consideration must be given to scheduling pilot tests to capture the water quality events that bearsignificant impact to the operation of the RO process. Such events include seasonal variations in temperature,turbidity, algae, taste and odors, synthetic organic compounds, etc.While much pilot data is available, few surface water RO or NF treatment systems have actually been built in theUnited States. This paper presents a review of the few facilities that currently exist or are in the planning orconstruction phases. These facilities include: Granbury, Texas; Barrow, Alaska; Wichita, Kansas; and, West Jordan,Utah.A review of existing and planned treatment facilities indicates that intake type and pretreatment required bearsignificant impact on treatment costs. Surface intakes typically require advanced pretreatment processes that mayinclude ultrafiltration (UF) or microfiltration (MF). However, some may operate well when using conventionalprocesses and media filtration. Types of intake structures and siting intake facilities, operation of conventionalpretreatment processes before RO or NF, and considerations that may lead to the implementation of advancedpretreatment processes are presented and discussed.Riverbank filtration can be used to reduce the seasonal impacts of particulate matter, organics, algae and algaerelated taste and odor problems. Interest in riverbank filtration is increasing due to the recently proposed Long Term2 Enhanced Surface Water Treatment Rule (LT2ESWTR), which may grant this process log-removal credits formicrobial pathogens such as Giardia and Cryptosporidium. Criteria for evaluation of hydrogeologic conditions thatindicate the feasibility of riverbank filtration are summarized. Includes 10 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

03/05/2003

Number of Pages:

12

File Size:

1 file , 290 KB