Virginia Law

A. Applicability. This section pertains to the use of membrane filtration as follows:

1. For pathogen and turbidity log removal credits in accordance with Table 500.1 in 12VAC5-590-500, the use of MF and UF are allowed.

2. For softening, total dissolved solids (TDS) removal, organics removal, and other treatment purposes, reverse osmosis (RO) and nanofiltration (NF) are allowed in accordance with 12VAC5-590-680 G.

B. Membrane filtration systems shall meet all requirements contained in 12VAC5-590-401 E 6 b to be granted removal credit for Giardia lamblia and Cryptosporidium.

C. A demonstration study shall be conducted on the water to be treated before the installation of a membrane filtration system unless the owner can demonstrate to the satisfaction of the department that the source water quality range over all four seasons of a year will be adequately treated by the proposed design.

D. All membrane treatment units for pathogen and turbidity removal shall employ MF or UF using hollow fiber, positive pressure-driven membrane filtration technology. They may employ either an inside-to-outside or outside-to-inside flow direction.

E. The number of membrane units shall be a function of the overall treatment facility capacity, waterworks capacity, and water demand. Multiple membrane units shall be provided where the treatment facility design capacity exceeds 0.5 MGD.

F. Approved materials and chemicals.

1. All membrane materials, associated piping, and other components in contact with the water shall be in accordance with 12VAC5-590-810.

2. Chemicals used in any membrane cleaning process shall be in accordance with 12VAC5-590-515.

G. Turbidity monitoring. Continuous indicating and recording equipment meeting the requirements of 12VAC5-590-770 B shall be provided for the following locations:

1. Source water;

2. Pretreated water, such as by coagulation, flocculation, and sedimentation (if applicable);

3. Filtrate from each membrane unit; and

4. Combined filter effluent, where more than one membrane unit is installed.

H. Indicating and recording equipment for entry point chlorine residual monitoring shall be provided. Indicating and recording equipment for filtered water temperature monitoring shall be provided.

I. Pressure monitoring:

1. Indicating equipment shall be provided for monitoring the pressure drop across any prefilter.

2. Indicating and recording equipment shall be provided for monitoring the pressure drop across membrane modules, (i.e., transmembrane pressure).

3. Integrity monitoring. Indicating and recording equipment for direct integrity test monitoring shall be provided and shall document the date, time, and results of every test performed on each unit.

J. Flow measurement. Equipment shall be provided for measuring or calculating the following flows:

1. Source water, gpm and totalized;

2. Filtrate from each unit, gpm and totalized;

3. Flux from each unit, gpd/sf;

4. Recirculation to each unit, gpd or percent of feed flow, if applicable;

5. Entry point, gpm and totalized; and

6. Waste.

K. An alarm system shall be provided that will report alarm conditions and shut down the treatment plant and entry point flow as necessary.

1. All alarms shall be reported to a location manned 24 hours per day or to a person on call and shall report alarm conditions audio-visually at the water treatment plant.

2. At a minimum, the following points shall be monitored by the alarm system. Alarm and shut down set point conditions will be determined by the department on an individual basis.

a. Feed water flow;

b. Feed water turbidity, if required by the department;

c. Filtrate turbidity from each unit exceeding operational control criteria;

d. Membrane direct integrity test initiation, failure, and exceeding operational control criteria; and

e. Entry point disinfectant residual.

L. Sample taps shall be provided to monitor the following:

1. Source water;

2. Source water storage tank effluent;

3. Feed water after prefiltration;

4. Filtrate from each membrane unit;

5. Combined filtrate from all units;

6. Entry point; and

7. Additional sample taps to monitor the presence of cleaning solutions used in either the backwash or cleaning operations.

M. Equipment shall be provided, using variable frequency drive or other suitable means to adjust the feed pump output in order not to exceed the design flux in the event modules are taken off line.

N. Pressure gauges.

1. A portable, pocket-type pressure gauge of the correct range and accuracy for the application and with the capability of being calibrated shall be provided to check the pressure readings of the pressure transducers installed on the membrane units.

2. At each location of a pressure transducer, a 1/4-inch diameter pressure gauge with American National Standard Taper Threads (NPT) connection shall be provided to facilitate the connection of a portable, pocket-type test gauge.

O. Clean-in-place systems, including tanks, piping, all joints, and valves, shall be compatible with the cleaning solution and shall be corrosion resistant.

P. An operation and maintenance manual shall be provided for all membrane filtration treatment units. The operation and maintenance manual shall include the following:

1. A maintenance schedule for each piece of equipment.

2. Operation procedures, including software user instructions.

3. A troubleshooting guide.

4. Identification of specific proprietary equipment or software not available to the owner or operator.

5. A service call number.

6. DIT requirements.

7. Chemical cleaning instructions.

8. A detailed description of the treatment units and the control of each unit for optimal performance.

Q. A means shall be provided to isolate a compromised module or fiber or both. A means to visually inspect modules while simultaneously conducting the DIT shall be provided. Alternatively, sonic testing equipment that provides a relative accelerometer reading shall be provided where visual inspection cannot be performed.