# Presentation: 543274

## POU/POE for Arsenic Removal

## Point-Of-Use (POU)

**Treats water at a single tap**

## Installed POU RO Unit

**Notes:**
This is a picture of a typical POU RO installation.  Note the large white storage tank to the right of the cartridges.  Because RO has a low instantaneous production rate, it is generally necessary to install a 3+ gallon storage tank to ensure that residents have enough water on demand for cooking or drinking.
Many different POU RO configurations exist and are generally identified by the total number of cartridges in the unit.  A four stage RO is a typical configuration, consisting of a sediment pre-filter, a GAC pre-filter, the RO membrane, and a GAC post-filter.

## Point-Of-Entry (POE)

**Treats all water entering a building**

## Installed POE AA

**Notes:**
This picture is of a full-scale AA system installed at a small PWS in Massachusetts.  However, it only serves an apartment building and is representative of what one might install for POE for an apartment building in a small community where POE AA is selected as a compliance option for the whole community.  This system is larger than what you might expect for POE AA for a single home, but illustrates the point that when selecting POE as a compliance option for a community, you have to make adjustments for commercial buildings and larger dwellings.

## Safe Drinking Water Act

**List of feasible technologies for small communities – POU and POE**
**Owned, operated, and maintained by PWS**
**Mechanical warning device**
**POU and POE not for microbials**
**ANSI certification**

## SDWA

**(i) In general.— **Each national primary drinking water regulation which establishes a maximum contaminant level shall list the technology, treatment techniques, and other means which the Administrator finds to be feasible for purposes of meeting such maximum contaminant level, **but a regulation under this subsection shall not require that any specified technology, treatment technique, or other means be used for purposes of meeting such maximum contaminant level. **

## Applicable Regulations

**40 CFR 141.100 (****specific to POE****)**
**PWS must own and operate**
**State approved monitoring plan – equivalent health protection as central treatment**
**State approved application plan (performance certification, field testing, engineering design) and microbial protection**
**40 CFR 142.62 (****POU and POE for variance and exemptions****)**
**Arsenic Rule - SSCTs for arsenic removal (for systems serving 10,000 or fewer):**
**POU Reverse Osmosis**
**POU Activated Alumina**

**Notes:**
The SDWA contains the following requirement for POU devices only:
 EPA cannot list POU as an affordable technology for compliance with an MCL or treatment technique for a microbial contaminant or indicator of a microbial contaminant.
The SDWA also contains the following requirements for both POU and POE devices:
Must be controlled and maintained by the PWS.
Must have mechanical warnings to automatically notify customers of operational problems.
Where ANSI standards have been issued, only units meeting these standards may be used in a compliance strategy.
The language in 40 CFR 141.100 is specific to POE devices and does not address the use of POU devices for compliance with NPDWRs.  
The POE language in 40 CFR 142.62 addresses both POU and POE devices used under a variance or exemption.  The language in 142.62 is very similar to the language in 141.100.
In the recently promulgated Arsenic Rule, POU RO and activated alumina are listed as small system compliance technologies (SSCTs) in 40 CFR 141. 62.  

## ANSI/NSF Standards

- Standard 44:  Cation Exchange Water Softeners
**Standard 53:  Drinking Water Treatment Units- Health Effects**
**As (V) - <= 50 ppb and <= 300 ppb**
**AS (total) proposed  [<= 300 ppb]**
- Standard 55:  UV Water Treatment Systems
**Standard 58:  RO Drinking Water Treatment Systems**
**As (V) - <=50 and <= 300 ppb**
**Drinking Water Chemicals and Components – 60 and 61**

**Notes:**
The SDWA states “If the American National Standards Institute has issued product standards applicable to a specific type of point-of-entry or point-of-use treatment unit, individual units of that type shall not be accepted for compliance with a maximum contaminant level or treatment technique requirement unless they are independently certified in accordance with such standards.”
This slide lists the existing ANSI/NSF standards applicable to POU and POE.
It is important to note that ANSI/NSF certified devices do not exist for all contaminants.  For instance, only one POU adsorptive media device currently exists for arsenic removal that is ANSI/NSF Standard 53 certified.  More should be commercially available since this technology is rapidly developing.
NSF/ANSI Standard 60
NSF/ANSI Standard 60, first adopted by the NSF Board of Trustees on October 7, 1988, covers corrosion and scale control chemicals; pH adjustment, softening, precipitation, and sequestering chemicals; coagulation and flocculation chemicals; well-drilling products; disinfection and oxidation chemicals; and miscellaneous and specialty chemicals for treatment of drinking water. The standard addresses the health effects implications of treatment chemicals and related impurities. Both the treatment chemical and the related impurities are considered contaminants for evaluation purposes. The two principal questions addressed are:
Is the chemical safe at the maximum dose, and 
Are impurities below the maximum acceptable levels? 
Reaction by-products such as the disinfection by-products of chlorine, ozone, hydrogen peroxide, or other chemicals are not covered by this scope of the standard.
NSF/ANSI Standard 61
NSF/ANSI Standard 61, also adopted on October 7, 1988, covers indirect additives products and materials, including process media, protective materials, joining and sealing materials, pipes and related products, mechanical devices, and mechanical plumbing devices (including faucets). In essence, every material from the well or water intakes through to the faucet are covered. 
NSF/ANSI Standard 61 addresses crucial aspects of drinking water system components: whether contaminants that leach or migrate from the product/material into the drinking water are above acceptable levels in finished waters. Standard 61 also requires evaluation of certain materials that have potential to support microbiological growth. Such materials include solvent-based coatings, gaskets, etc.
The standard also covers products, components and materials. When a material is certified under Standard 61, its certification indicates use restrictions on parameters such as maximum use temperature or surface area to volume ratio when the material is used in a finished product. This option allows manufacturers using certified materials to bypass some or all chemical and microbiological testing when seeking certification, and assures that finished products meet all requirements.

## Installed ANSI/NSF Certified POU Adsorptive Media Unit

**Multi-Pure MP880SB**

**Notes:**
The pictured device (Multi-Pure MP880SB) is the only NSF certified POU (plumbed-in to separate tap) adsorptive media unit currently on the market.  However, others may be undergoing the certification process.  When selecting a POU or POE device for compliance it is important to check the most current NSF listings.
Water enters the filter through a graded density pre-filter, then passes through a highly compacted solid carbon block filter.  The carbon block filter is a blend of activated carbon and a specialized arsenic-adsorptive media.  Finally, the water passes through a post-filter.  All of these components are contained within the housing shown in the picture on this slide.

## POU/POE Considerations

**Water Quality**
**User agreements**
**Local ordinances**
**Lot use agreements (trailer courts,...)**
**Homeowners association**
**Access to homes**

**Notes:**
Water quality issues that should be considered are discussed in more detail on the next slides.
Homeowner agreements may be necessary to ensure homeowner cooperation in implementing a POU or POE treatment scheme and to ensure access to homes for maintenance and repair.

## Water Quality Considerations

**AX**
**Competing Ion: sulfate**
**AX not recommended if sulfate ****≥**** 150 mg/L**
**Susceptible to fouling by iron, magnesium, and copper**

**Notes:**
AX resins preferentially removes sulfate over arsenic. Therefore, the removal efficiency of an AX system will be closely tied to the concentration of sulfate in the influent.  Higher sulfate concentrations will cause shorter run lengths.  AX is generally considered uneconomical (due to short run lengths) if the sulfate concentration is 150 mg/L or higher.  It is always important to pilot test before installing any POU or POE treatment technology to ensure that competing ions in the water will not interfere with the POU or POE device’s ability to effectively and economically remove the contaminant of concern.
AX resins are susceptible to fouling by iron, magnesium, and copper.  Channels may develop in the resin bed if the pressure drop across the bed is too high due to fouling.  This may permit water to pass through the unit without adequate contact with the treatment resin.  Periodic backwashing will help prevent fouling of the resin bed and will remove sediment build-up that inhibits system performance.

## Water Quality Considerations

**AA**
**Optimal pH for arsenic removal is 5.5 to 6.0**
**pH adjustment typically not feasible for POU AA**
**Competing ions: silica, fluoride, phosphate, sulfate and dissolved iron and manganese**
**Iron-based media**
**pH ****≤ ****8.5**
**Not as sensitive to competing ions**

**Notes:**
While arsenic is highly preferred by AA and iron-based adsorptive media, arsenic removal can be inhibited by several factors related to the source water.  One factor is the feed water pH. With AA, arsenic removal is notably better when the pH of the feed water is between 5.5 and 6.0.  This is because hydroxide ions, the only ions more preferred by AA than arsenic, are more prevalent at higher pHs, and therefore compete with arsenic for available sites. 
Another factor inhibiting arsenic removal by AA is the presence of interfering or competing ions such as silica, fluoride, phosphate, sulfate and dissolved iron and manganese. 
Iron-based media have better arsenic removal over a broader range of pH but manufacturers still do not recommend exceeding a pH of 8.5. Iron-based media are typically not as sensitive to competing ions as AA.

## Water Quality Considerations

**RO**
**Cellulose acetate membranes (CAMs) can withstand some chlorine**
**Chlorine damages thin-film composite polyamide membranes (TFMs)**
**Chlorine should be ****≤ ****0.1 mg/L**
**May use a GAC pre-filter to remove chlorine**
**Ferric iron, manganese, aluminum**
**	****< 0.05 mg/L each (can cause fouling)**
**Excessive particulate can cause fouling**

**Notes:**
Many POU RO devices use TFMs.  Typically, these devices are equipped with a GAC pre-filter to remove chlorine and avoid damaging the RO membrane.
Aluminum, iron, and manganese can all cause fouling of RO membranes.  In addition to causing a loss of performance, iron fouling can make the membrane more susceptible to oxidation damage (Dow Liquid Separations, 2004).  Pretreatment with oxidation/filtration is an effective way to remove both manganese and iron.  Pretreatment with media filtration is one possible method to remove aluminum. 
Pre-filtration may be necessary to prevent membrane fouling if excessive particulate is present.  Pilot testing may be necessary to determine whether pretreatment is needed.  Typically, POU RO devices are equipped with a 5 micron pre-filter to remove particulate.

	Source: Dow Liquid Separations.  2004.  FILMTEC Reverse Osmosis Membranes Technical Manual. Form No. 609-00071-104.  Dow Chemical Company.   Midland, Michigan.

## Water Quality Considerations

**For all POU and POE technologies:**
**On-site pilot testing is important. **
**Combinations of contaminants in the water may reduce the effectiveness of a technology, even when basic water quality criteria are met.**

**Notes:**
The need for pilot testing is strongly supported by the experience of other systems that have installed POU and POE treatment devices as part of a compliance strategy. Several systems found that the treatment devices they had initially planned to install did not operate properly (i.e., did not adequately reduce the concentration of the contaminant of concern in finished water) due to the combination of contaminants present in local waters. As a result of prior testing, these systems installed appropriate units, avoiding unnecessary costs, and were able to achieve better levels of contaminant removal.

## Design Considerations

**POU RO**
**CAM (cellulose acetate) vs. TFM (thin film)**
**TFM has higher contaminant removal efficiency, but lower chlorine tolerance**

**Notes:**
CAM = cellulose acetate membrane
TFM = thin-film (composite polyamide) membrane

## Design Considerations

**POU RO**
**Water recovery rate**
**POU RO - Typically only 25 to 30% of influent volume becomes treated product water**
**Remainder becomes concentrated waste stream**
**May not be suitable in arid regions**

**Notes:**
A recovery rate of 25 to 30% means that 70 to 75% of the water entering the POU RO unit becomes waste.  Recovery rates for centralized RO treatment are much higher.

## Design Considerations

**All POU and POE technologies:**
**Need to consider household demand**
**RO approx. 1 gph**
**Adsorptive media approx. 5 gph**
**May need larger devices for some households **
**May need storage depending on instantaneous production rate of device**

**Notes:**
When selecting POU devices for a community, it is important to remember that all households and business may not be able to use the same treatment device.  For instance, commercial businesses and restaurants may need to have POE devices installed to supply sufficient water at all necessary taps even though the average household will only need to have a POU device installed.  In addition, larger households may need larger POU or POE units.  For adsorptive media or AX units this may mean additional or larger tanks or cartridges of media.
POU RO units typically treat water continuously for a total of 20 or 30 gallons of treated water per day.  This means that these devices produces about 1 gallon of water per hour or about 60 milliliters per minute.  In order to have sufficient flow for the user on demand, POU RO units typically include a 5+ gallon storage tank.
Most POU AX or adsorptive media units can treat water at a rate of 5 gallons per minute or more.  Therefore, these devices are typically not equipped with a storage tank.

## Residuals

**Solids**
**Spent cartridges, media, resin, membranes, bulbs, filters, etc.**
**Liquids**
**Spent backwash**
**Spent regenerant**
**Waste brine**

**Notes:**
The residuals that can be generated by the POU or POE devices are:
Solid residuals, such as spent cartridges, media, resin, membranes, bulbs, and filters that require disposal at the end of their useful life.  Disposal may occur several times a year or less frequently.
Liquid waste streams will be generated by POU RO systems and POE IX, GAC, and adsorptive media systems if backwashed or regenerated.  POU RO units produce a waste brine which is characterized by high contaminant concentrations.  Backwashing and regeneration, required for proper operation of most POE IX, GAC, and adsorptive media treatment devices, will also result in the generation of intermittent liquid waste. 
The quantity and characteristics of the residuals will vary based on the treatment technology used, contaminant(s) being removed, source water characteristics, and other site-specific operational conditions.  In order to properly assess the quantity and quality of the residuals, pilot testing should be done.

## Residuals Disposal

**Conduct pilot testing to determine quantity and quality of residuals**
**POU and POE residuals generated in individual households exempt from Federal regulations as hazardous waste under RCRA**
**However, State regulations and implementation may vary.  Contact State on this issue before implementing a POU or POE strategy.**

**Notes:**
Because the residuals generated by POU and POE units installed in residences are collected from individual households, these wastes will be exempt from Federal regulations as hazardous wastes under RCRA.  However, State regulations and each State’s implementation of Federal regulations can vary.

## Residuals Disposal

**Solids**
**Generally can be disposed of in household waste, delivered to a landfill, or regenerated.**
**Liquids**
_**May usually**_** be discharged to a POTW, on-site septic system, or dry well.**
**POTWs may issue limits for discharge of certain contaminants**
**May require special handling and disposal if high concentrations of certain contaminants are present**

**Notes:**
Solid residuals produced by these treatment systems often can be disposed of like normal household waste, delivered to a local landfill or regenerated.
Liquid residuals may usually be discharged to POTWs (upon approval from the POTW), on-site septic systems (may require a permit from the State or local agency), or dry wells (may require a permit).
In the case of liquid residuals, POTWs may issue their own limits for the discharge of certain contaminants, such as copper and TDS.  However, waste that contains high concentrations of certain contaminants may require special handling and disposal. 

## Residuals Disposal

**Commercial establishments**
**May also be exempt from RCRA if**
**Quantity of hazardous waste generated is considered small (defined in 40 CFR 261.5 as no more than 100 kg in that month)**
**Should contact State or local regulatory agency to assess proper classification and disposal**

**Notes:**
POU and POE devices installed in commercial or business establishments may also be exempt from RCRA if the quantity of waste generated is considered small (defined in 40 CFR Section 261.5 as generating no more than 100 kilograms of hazardous waste in that month).  For these types of installations, the system should contact the appropriate State or local regulatory personnel to assess proper classification and disposal of waste.

## Costs

**Alaska and Oregon Case Study (1983 $)**
**AX units - $350**
**AA units - $250**
**RO units - $292**
**Lummi Island – POE-AX (2001 $)**
**Base unit $2500 (Average $3400 - $2500-$8000)**
**NAS Fallon – POU-RO (2001 $)**
**RO units $300 installed **
**Annual maintenance $129**

**Cost Evaluation of Small System Compliance Options: Point-of-Use and Point-of-Entry Treatment Units – Under Development**

**Notes:**
Lummi Island

## AZ Arsenic Master Plan – POU Cost Estimates

**Avg. Household – 3 people/house – 1gal/day/person**
**Installation costs - $150**
**Equipment cost – RO-$350 and Adsorption-$150**
**Labor costs - $25-installer and $50 administration**
**Cost of analysis - $12/sample**
**Media replacement – RO $95 and Adsorption-$75**

## Cost Overview - AZ

**Notes:**

Slide from Shannon Murphy – Watts Premier
Please feel free to use the slide. 
Regarding where I got the numbers - they are based upon the work that I have done with communities here in AZ using our units, but also represent a "worst case" scenario, as it takes in to account replacement of the RO membranes every other year. We expect membranes to last 2 - 5 years, but did not want to put together a cost overview with 5 year replacement, and then have a community install and have to replace every other year.  As a reference point, the units installed in late 03 are running fine, and look like they will keep going strong. So their cost will be less. 
Regarding the centralized treatment numbers, this is information from the Arsenic master plan that ADEQ put together, as well as some reports that the EPA has used regarding centralized treatment.

## Case Studies

## Case Study – Grimes, California

**POU Adsorptive Media**

## Slide 28

## Grimes, CA

**NSF/EPA Demonstration Project**
**Supplemental funding from NSF and Kinetico**
**System demographics**
**122 installations (2 RO)**
**104 residences**
**18 other sites (e.g., school, post office, businesses, day care, etc.)**

**Notes:**
This case study was conducted as an NSF and EPA sponsored demonstration project to identify, measure, and record conditions for successful implementation of centrally managed POU treatment for compliance with the SDWA.
However, the system and the California Department of Health Services will decide if this project will work for compliance after the study is complete. 
If so, the system will continue to receive cartridges will be provided to Grimes at a discount for three years after study.  Ownership of the POU units will also be transferred to the system after the study.

## Grimes, CA

**POU AA**

**Notes:**
This slide shows a schematic of the POU AA unit used in the study.  Note that there are two AA cartridges followed by a GAC cartridge for taste and odor.  This device is not NSF certified. The NSF arsenic standard was not final at the time this study was undertaken.  However, the device was tested against the draft arsenic standard and all other provisions for certification were met.

## Grimes, CA

**POU GFH**

**Notes:**
This slide shows a schematic of the POU GFH unit used in the study.  Note that there is one  POU GFH cartridge followed by a GAC cartridge for taste and odor.  This device is not NSF certified.

## Grimes, CA

**Conclusions**
**As raw water 20-50 ug/L****As finished water <10 ug/L (all but 2 samples)**
**No replacement within 1 year**
**POU units were donated**
**Monitoring:**
**Analyzed composite sample from 5 POU devices after installation**
**Samples taken quarterly from then on**
**Passed CA WET and TCLP tests**

**Notes:**
The AA cartridges were expected to treat 500 gallons before replacement and the GFH cartridges were expected to treat 900 gallons before replacement.  The length of time will depend on water use.  If an average household water usage rate of 1.3 gallons per day (based on national household size and water use data) is assumed, the expected life of the AA unit would be just over one year and the expected life of the GFH unit would be just under 2 years.
The POU units in this study and installation were donated to the system by Kinetico.
Every POU device was sampled on installation.  Composites of five units were analyzed to save analytical cost.  They sampled quarterly from then on. The sampling plan assured that every home was sampled at least once more.  Sampling was weighted to the end of the study; e.g. there were more samples in the last quarter than the first.
Spent cartridges from both types of units were tested and passed the CA WET and TCLP tests.

## Case Study – Lummi Island, Washington

**POE Anion Exchange**

## Lummi Island, WA

**POE for Compliance – not a demonstration project**
**System Demographics**
**Subdivision with homeowners association**
**Approximately 10 homes **
**Classified as Group B water**
**	****system (not a PWS)**
**Decision**
**Central treatment vs. POE**

**Notes:**
This POE system came about because a landowner tried to develop lot in the subdivision, but was unable to obtain financing due to high arsenic levels in the subdivision’s well.  The landowner first investigated centralized AX, but the Washington Department of Ecology would not approve a discharge permit for a new drainfield.  The Department of Ecology was concerned that AX regeneration might create a hazardous waste stream.
The landowner investigated alternatives and eventually proposed POE AX in each home served by the water system.  Since spent regenerant and backwash would be discharged to individual homeowner’s drainfields, a discharge permit would not be necessary.
Ultimately, the system received approval for POE AX at individual homes, contingent on the following:
System must have a certified operator
POE units must be checked monthly
Subsequent homeowners must be notified of POE units
Must demonstrate that POE units could be checked in field with simple test

## Lummi Island, WA

**Notes:**
Preliminary pilot testing showed pre-oxidation is not necessary for effective arsenic and cyanide removal.
The two tanks are operated in parallel to allow continuous operation during backwash and regeneration (only one tank off-line at a time).
The tanks are operated in downflow mode for treatment and in upflow mode for regeneration and backwash.
This Kinetico system uses Purolite C100 cation resin for removal of iron and/or hardness and Purolite A-300 anion resin to remove arsenic and cyanide.  The sodium from the sodium chloride regenerates the cation resin and the chloride regenerates the anion resin.

## Lummi Island, WA

**Conclusions**
**Approval process took about 4 years**
**Media expected to last about 5 years**
**Expect to dispose of media in household trash**
**$2,500 (base) for POE AX**
**Modifications may be necessary to meet new arsenic MCL**
**Homeowners considering switch to iron-based media**

**Notes:**
The approval process took about 4 years due to pilot testing and substantial paperwork.  The Homeowners association had to develop an O&M manual for all homeowners before receiving approval for the use of the POE AX devices.  The first pilot test was a one-day preliminary test to determine if oxidation was necessary and whether the unit would effectively remove arsenic from the system’s water.  The second pilot test lasted  months.  The goals of the second pilot test were as follows:
Evaluate flow rate and run length,
Verify that simple test can be used for routine evaluation of POE system,
Confirm that treated water remains free from coliforms,
Verify that pH drop after regeneration not a concern in successive cycles,
Verify that preoxidation not required, and
Verify effectiveness of backwash and regeneration.
The cost of the POE AX units shown on this slide includes initial and follow-up annual sampling by the vendor during the first year.  The more expensive AX units also remove excess sodium.
The homeowners are considering alternatives because the POE AX units may not meet the new MCL for arsenic.  The units can treat to below 0.010 mg/L, but levels may rise to 0.02 mg/L by the end of treatment cycle.

## Case Study – Fallon, Nevada

**POU Reverse Osmosis**

## Slide 38

**Notes:**
In this case study, the Naval Air Station (NAS) installed the POU RO devices as an interim measure.  The NAS had its own wells, which had high levels of naturally occurring arsenic.  The City of Fallon also has high arsenic in its source water and needed to construct treatment to remove it (city is too large to have considered POU/POE as solution).  Therefore, the City of Fallon and NAS Fallon collaborated to build an arsenic treatment facility in the City of Fallon.
NAS Fallon connected to the new arsenic treatment facility in April 2004.  Therefore, there is no further need for the POU RO devices.

## Fallon NAS, NV

**Naval Air Station**
**360 POU RO units installed in base quarters**
**75 water cooler style RO machines installed in common areas**
**11 RO vending machines for on- and off-base residents to fill bottles**

**Notes:**
The Naval Air Station in Fallon, Nevada (NAS Fallon), is made up of offices, living quarters, and various other base facilities.  Treated water needed to be available to all personnel working and/or living on the base so a variety of types of RO devices were installed to provide safe drinking water to everyone.

## Fallon NAS, NV

**Notes:**
This slide shows a schematic of the RO configuration used in this case study.  Note that the device contains a sediment pre-filter, carbon pre- and post-filters, and storage.

## Fallon NAS, NV

**POU RO Costs**
**$300 per unit for purchase and installation**
**$129/yr per unit for maintenance and parts replacement**
**$9 sediment pre-filter cartridge**
**$12 per GAC filter cartridge**
**$55 per RO membrane cartridge**

**Notes:**
The cost of maintenance for these units is high because the vendor is 65 miles from the base.  The units are serviced quarterly and tested twice per year.

## Fallon NAS, NV

**Conclusions**
**As raw water 100 ug/L****As finished water < DL**
**Military base is unique case for POU**
**Military indoctrination process **
**Access to residential POU RO units**
**POU RO installed as temporary measure**

**Notes:**
This case study is a unique scenario because it was undertaken on a military base.  The military already has an indoctrination process in place for new residents and employees which facilitated public education about POU devices.  In addition, the navy has mechanisms already in place to guarantee access to housing for inspections.  This ensured access to the POU RO units for maintenance and monitoring.
POU RO was considered only a temporary measure as the City of Fallon and the NAS were cooperating to construct an arsenic treatment facility to serve both the city and the naval air station.  Fallon NAS connected to the city water treatment plant in April 2004.

## RO – POU: School

**Provides water to the kitchen and drinking fountains**

## Summary

**Has application for some public water supplies (small??)**
**Has the same water quality considerations as central treatment**
**Costs are declining**
**Must be well-tested at the system**
**Must have state approved operation, maintenance, and monitoring program**
**Must provide equivalent public health protection.**