What the Flux!

Polymeric vs Ceramic Membranes

My sales rep in the Southeast came to me recently concerned that ceramic membrane companies are promoting fluxes to engineers and water utilities in the region in excess of 200 gfd, asking me how polymeric membranes can compete? My response was WTF! Flux is just a number and just because the flux may seem a lot higher than polymeric membranes it does not mean a ceramic system has a smaller footprint or lower cost. I’ve seen a lot of presentations from ceramic membrane companies trumpeting all the reasons ceramic is better than polymeric but I haven’t yet seen a counter argument from a polymeric membrane company or system supplier. So maybe this is the first counter to some of the ceramic membrane company’s claims. I know I’ll get a push back from the ceramic membrane companies because they are all trying to get established in the market, but I can’t just sit back and let the latest polymeric membranes be unjustly grouped with systems of the past. Note that I am not criticizing the integrity or performance of ceramic membranes at all, and there are situations where these are a great fit, but rather I am just trying to provide a balanced and up to date comparison with polymeric membranes.

WTF!*

Let’s start with the high flux claims. I have seen papers on ceramic pilot studies where fluxes up to 200 gfd have been tested but I don’t yet know of a full-scale system in the US that has been put in service with a design flux this high. The largest ceramic membrane system in the US at Butte MT has a design flux of 69 gfd. A ceramic system that was awarded at Mandaree ND a few years ago had a design flux of 120 gfd for summer. These are pressure ceramic systems where there are feed pumps supplying pressurized modules. 

Figure 1: Membrane System Configurations

The other ceramic configuration is submerged flat sheet operating in the vacuum configuration where a pump draws through the membranes (see Fig 1). Companies such as Cerafiltec and Ovivo are providing this submerged technology and are particularly active in the Southeast. I don’t think a flat sheet submerged ceramic system is installed in the US on a full-scale drinking water system yet, but I have seen several pilot study papers. What strikes me about these recent pilot studies is they are not that impressive. I won’t call out any specific studies, but go search the proceedings from recent AMTA/AWWA Membrane Technology Conferences and you will find them (there may be better pilot studies but I can't find any published). They all spend a lot of time optimizing coagulation ahead of the membranes to reduce rapid TMP buildup and then ramp up the flux in steps over 1 to 2 week periods to get to 200 gfd.  I haven’t seen more than a few weeks operation at anything near 200 gfd in the published papers. Whenever I’ve been involved in a pilot study with polymeric membranes it has been necessary to run at stable operating conditions for at least 30 days. Why is the bar lowered when ceramic membranes get evaluated? Note the Mandaree ND ceramic pilot study did have stable operating periods of at least 30 days at 120 gfd.

 Another criteria for setting design conditions for polymeric membranes is to be a little conservative on the design flux compared to what the manufacturers or pilot studies claim is possible, so if a pilot study shows a flux of 60 gfd is possible based on the feed water quality, the engineer will allow 50 gfd for the full-scale system. While the ceramic membrane companies may claim 200 gfd is possible, when it comes to the design, I haven’t seen more than 120 gfd allowed. Even so, polymeric membranes can be disadvantaged from years of full-scale experience and require a more conservative design flux while ceramic membranes can claim aggressive fluxes without past full-scale experience to suggest otherwise.

 Does Ceramic have a Smaller Footprint?

The claim is often made or implied that due to higher fluxes, ceramic membrane systems have a lot smaller footprint. I will prove to you that is absolute baloney! Let’s look at the comparative footprints of polymeric and ceramic systems. For polymeric, I’m going to use Toray’s HFUG-2020AN module which has 969 sq.ft. of surface area and is probably the most popular polymeric membrane on the market currently. Compare this with a Nanostone ceramic module at 258 sq.ft. per module. A Nanostone module has around the same diameter as a Toray module and is around 9 inches shorter, so the footprint of a membrane rack is the same for both modules (ie. a rack with 40 Toray modules is the same size as a rack with 40 Nanostone modules). Therefore, a Nanostone module needs to have 3.8 times the flux of a Toray module just to have the same footprint based on surface area per module. So, if the polymeric module is designed for a 50 gfd flux, the flux through the Nanostone module needs to be 190 gfd to match the Toray module footprint. If the design flux for ceramic is 150gfd, the Toray system at 50 gfd will have a smaller footprint.

 Now let’s look at a Cerafiltec flat sheet submerged system. These membranes are supplied as 64.6 sq.ft. modules that have a footprint of 28” x 22.7”. Based on Cerafiltec’s website, these modules can be stacked in towers 16 high, so that would add up to a surface area of 1034 sq.ft. From the photos I have seen on the website, the tallest I saw was 8 high, but I will be conservative and compare the footprint of a 16 high tower versus Toray modules in the same footprint. The Toray modules are 8.5” diameter, so within the footprint of the ceramic flat sheet tower, you could conservatively fit 4.5 Toray modules allowing for spacing between the modules (see Fig 2). Therefore a Cerafiltec tower at maximum height needs to have 4.2 times the flux of a Toray module to have the same footprint, i.e. if the Toray module flux is 50 gfd, the submerged ceramic system needs to flux of 210 gfd to match the footprint.

Figure 2: Polymeric versus Ceramic Footprint Comparison

So, I hope I have made it clear that flux is just a number and a high flux does not mean that a membrane system will have a smaller footprint. You also need to consider the amount of membrane surface area that will fit within a given footprint and that ceramic modules have a lot lower surface area than polymeric modules. The price of a ceramic membranes compared to polymeric modules on a membrane surface area basis is also a lot higher, so you can’t assume a higher flux also means a lower cost.

 Of course, there are other important considerations when comparing polymeric to ceramic membranes such membrane longevity and lifecycle cost. I have mentioned in a previous post that the longevity of the newer polymeric membranes is much improved over earlier polymeric membranes which has narrowed the lifecycle benefits of ceramic over polymeric. I’ve also calculated that when you consider the requirement of a coagulant dose ahead of ceramic membranes, the lifecycle cost of polymeric membranes can be lower than ceramic. I will elaborate on that in a future post.

*Shoutout to Stuart Leak from Avista who first used this acronym in his presentation What the Foulant.

The comments and opinions in this post are my own and not those of my employer.

PFAS Discharges into Sand Creek from Suncor’s Denver Refinery Must Stop

Suncor Refinery alongside Sand Creek - Photo by Hyoung Chang, Denver Post

I have been stewing over whether to do a post on an article I saw in the Denver Post on July 27, 2023, regarding discharges of PFAS from Suncor’s refinery in the Denver area into Sand Creek which eventually makes its way to the South Platte.  For years I have been hearing local news stories of concerns from nearby communities about air emissions from the refinery and allegations of exceeding EPA and Colorado Department of Health and Environment (CDPHE) permit levels. I have wondered if Suncor has been given some slack due to its position as a major fuel supplier in the region. Whenever the refinery is offline due to maintenance, etc., fuel prices spike which impacts the wider community’s hip pocket (does anyone keep their wallet in their hip pocket anymore?). Is that allowing Suncor some leverage over CDPHE’s permitting process? According to the Denver Post article, Suncor had been operating on an air quality permit from 2006 that is supposed to be updated every 5 years. The permits for water and stormwater discharges were last updated in 2012.  Of course, having a permit does not mean Suncor adheres to it and there have been reported incidences of benzene spills into Sand Creek over the years as well as air permit exceedances.

South Platte’s PFAS Problem

Being in the water industry and seeing the great expense many water utilities and communities are facing to meet upcoming PFAS regulations, when I read about how such high levels are being discharged from Suncor into a drinking water source used by so many Coloradans it really hit a raw nerve for me. Pretty much any water treatment system taking water from the South Platte in the Denver Metro Area and East, including nearby wells, will have to implement some sort of treatment for PFAS removal. The cost for treatment is in the millions to tens of millions of dollars each, depending on system size. While the drinking water PFAS regulations are still being finalized, many water systems are already making plans to install treatment, since it can take years to get the funds and construct the required treatment equipment (typical solutions are GAC, Ion Exchange or Reverse Osmosis).

Suncor’s source of PFAS is likely firefighting foams used onsite, although I’m not familiar with refining to know if any raw materials contain PFAS also. This contaminates groundwater under the refinery and according to the Denver Post, Suncor treats this groundwater before releasing to Sand Creek, although obviously it not treated for PFAS removal yet. Admittedly, PFAS has only been identified as a concern in drinking water relatively recently (since 2016) and drinking water regulations are still being finalized. But Suncor was issued a draft permit by CDPHE in 2020 to release no more than 70 parts per trillion into Sand Creek. Note in June 2023 Suncor reported to the CDPHE a discharge level of 2,675 ppt…this is after Suncor apparently installed in interim treatment system to reduce PFAS to 70 ppt in early 2022.

The Denver Post article reported that Suncor estimated it would take 3 years and millions of dollars to build a permanent system to remove PFAS from wastewater before discharge into Sand Creek. Suncor also said PFAS removal is extremely difficult and treatment technologies are still in development. These statements really raise my hackles. First of all, established treatment technologies for PFAS are available now – Reverse Osmosis, Granular Activated Carbon (GAC) and Ion Exchange are well proven and already in use for PFAS removal by water utilities. Secondly, if the stormwater is already being collected for treatment, a lot of the hard work is already done and it would not be difficult to add GAC or ion exchange to the treatment train. Much larger treatment systems have already been installed on contaminated Californian ground water supplies in a quick response to the detection of PFAS and the interim regulations. So don’t try to say the technologies are not yet developed! Locally, there are also treatment systems installed at water utilities south of Colorado Springs where they detected PFAS in the ground water supply originating from a local military base.

While Suncor continues to discharge PFAS into Sand Creek, communities downstream are paying the price with their health and their money where the local water treatment plants must pay for treatment.

The article in the Post was written in late July, so Suncor may very well have accelerated installing treatment for PFAS removal since then, since the media is quick to report a violation but often slow to report on a resolution. If so, then I retract some of my vitriol for Suncor not taking action.

The comments and opinions in this post are my own and not those of my employer.

“So your saying there’s a chance” - Dumb Bid Evaluation Processes

 I saw a bid evaluation process recently for membrane equipment that I hadn’t seen in about 10 years. I thought this type of evaluation had seen its last days with the demise of the bids that only allowed the ‘big-three’ proprietary system suppliers (Pall, Memcor, Zenon). I guess there are some engineers/owners still living in the past who don’t realize that bidding processes of the old days are not relevant for evaluating between todays’ membrane system suppliers (MSSs).

This particular bid process required bidders to provide in one envelope (#1) a technical proposal, including qualification and experience criteria, and in the other envelope (#2) the pricing and other commercial information. The owner and/or owner’s engineer would review the technical proposal and select the best qualified submission and only open the pricing proposal for that bidder. If the price met budget they would start negotiations to award to that bidder without looking at pricing for any other bidders. Out of the four MSSs invited to bid, one of these was one of the big-three and would clearly have the most references and be chosen as having the best score out of the technical proposals. So why would the other three bother bidding? Maybe some would hope the favorite in the race did not turn up for some reason?

In the old days, the big-three would bid nearly everything to try get market share in a fast growing and evolving market. Well hello, the MF/UF market is now quite mature, MSSs are often bidding with the same membranes supplied by independent vendors and decisions on whether to bid or not are based on whether the project can be profitable rather than buying market share. So, if you don’t have an open and fair bidding process, there may be only one bidder, which does not look good for the writer of the specifications.

This bidding situation had the look of the engineer/owner really wanting to select one manufacturer while keeping that manufacturer’s price honest. As long as the price is within budget, that manufacturer’s price could be higher than all others and the owner would never know. These days for MF/UF system procurement it is common to see a prequalification stage where a short list is made of manufacturers based on experience, company financial stability, references, local service, etc and then these bidders have a competitive bid based on price. That way the owner and engineer are happy with the quality of the bidders and the owner gets the best price from these bidders.

Another bidding process that is a combination of the above has a scoring matrix where price (or NPV) is say 40-60 points out of 100, with the rest of the points spread across reference installations, local service capabilities and other factors. This evaluated bid process can still allow the engineer/owner to pick the MSS they prefer using the subjective scoring factors, as long as the pricing of the preferred vendor is not too high. But at least all bidders will get their prices considered and therefore more MSS’s will likely bid, even those scoring lower on the non-price factors. As Lloyd said in Dumb and Dumber “So your saying there’s a chance”. I still think this bid process is not ideal, but if it is an open bid with no favorite, I’ll take this this type of evaluated bid over the two-envelope lucky draw...

Of course, if I am in the shoes of the preferred manufacturer with the best experience, I’ll take the ol’ two envelope bid process but sooner or later when this process yields only one bidder, somebody will end up looking dumb…

The comments and opinions in this post are my own and not those of my employer.

Gasson Spices up Membrane Technology Conference Opening Session

(Not one of the keynote speakers)

This year’s Membrane Technology Conference (MTC) in Knoxville TN, February 20-23, saw a spike in attendance, almost back to pre-covid levels, with a definite buzz around the presentations and exhibit hall where attendees were excited to be back networking with colleagues and technology suppliers.

Christopher Gasson, Publisher of Global Water Intelligence, was a keynote speaker for the Opening General Session, along with Harry Seah, CTO of PUB. Christopher’s ‘State of the Global Membrane Industry’ presentation certainly provided a spicey opening to the conference with his description of ‘What’s Hot and What’s Not’. Some exhibitors in the audience that were on Christopher’s ‘Not Hot’ list may have begged to differ. These included manufacturers and developers of ‘Fancy Membranes’ which I assume referred to new chlorine resistant membranes and fouling resistant membranes among others. From a global market share perspective, he is probably correct, but companies such as ZwitterCo are likely not trying to take the place of traditional RO membranes and are content targeting niche markets.

Other technologies or technological trends on the ‘Not Hot’ list included higher recovery for seawater, higher flux RO membranes and lower pressure desal membranes.

On the ‘Question Mark’ list included ceramic membranes and Universal/Open Platform low pressure systems.

During questions, Hary Seah agreed to disagree on the potential for ceramic membranes where PUB is a big advocate of ceramic membranes at its plants in Singapore. I’ve given my thoughts on the ceramic market previously and copped some flak for saying it is a niche technology, but I would agree with Christopher on his position.

I also agree that the Universal/Open Platform low pressure market may have cooled a little now that there are many direct replacement modules available for Asahi (Pall), Memcor, Toray and Dupont modules, which gives some flexibility for future membrane replacements without needing a membrane rack to accommodate modules of different configurations. Also, the proliferation of non-proprietary MF/UF systems using modules from Toray, Dupont and others has taken some steam out of the need for Universal racks. I will flesh this out further in a separate post.

 On the ‘Hot’ list were higher recovery RO in industrial applications (not seawater) which I assume is technologies such as CCRO, Pulse RO and FRRO, polymeric NF (NX Filtration), RO/NF membrane spacers, brine mining and digital monitoring (AI). Christopher pointed out that NX Filtration is capitalized at over €500M with revenues of €8M last year, having investment characteristics of a start-up tech company and a lot of pressure to perform.

I must admit I haven’t been to many opening sessions at MTC, but this one was very well attended, possibly in anticipation of the speakers’ topics. The audience was not disappointed, and Christopher’s thought-provoking statements provided a great catalyst for discussion afterwards and set the stage for a very lively conference.

The comments and opinions in this post are my own and not those of my employer.

Good Projects Spoiled by Bad Contractor Selection

 

Something that really perplexes me is how engineers and owners can put so much effort into the design of a plant, ensuring equipment vendors and components are well qualified and tightly specified, then the project is put out to bid and awarded to the contractor with the lowest price. Then it is a crapshoot if the contractor has the experience or capability to complete the project….

The contractor is the most important part of the project. They are responsible for taking the process equipment specified and all the surrounding infrastructure and turning it into a functioning water treatment plant. So why are there so many instances where unqualified, low-bid contractors win these projects?

When an incompetent contractor runs into trouble with schedule or budget when he/she missed something in the specifications, he is going to do what he can to deflect the blame to try keep the project profitable and avoid LDs. That often ends up in conflict with process equipment vendors to improve schedule to make up for poor project management, and drawn-out payments to vendors because the contractor can’t get approval for achieving project milestones. So many times I have heard the excuse from contractors that they can’t pay for start-up because they haven’t been paid for the practical completion milestone. That is compete BS when the equipment has been delivered and started up months ago and the contractor can’t get his s - it together to finish the landscaping or install the toilets… Just as frustrating is when start-up is delayed for months because the contractor is behind with installation, meanwhile the component vendors for the process equipment must be paid, so we go back to the old story of the process equipment vendor also acting as a bank for the project… (see previous post). All of this leads to conflict between the owner, engineer, contractor and OEMs and nobody feels good about the project.

Don’t get me wrong, I’m not out to bash all contractors. I have worked with a lot of very competent water treatment system contractors. And process equipment vendors are not always without blame for delays and missing items in the specifications. I have also seen specs where it wasn’t clear who was supposed to provide some items, so nobody had them, which is on the engineer who wrote the specs. My gripe is really with the process of not prequalifying contractors and ending up with a rudderless ship of a project. Similarly, process equipment vendors should be pre-qualified and most of the time they are, but when they are not it opens up the possibility of any garage integrator throwing in a price. Which takes me back to my original point – why spend so much time designing and specifying a plant and then leaving the execution in the hands of a random low bidding contractor?

Don't Blame the Pandemic

Admittedly, these days in some cases it has been hard to find contractors to bid projects. So, standards may be lowered to get competitive bids. Before a job goes out to bid, there has to be an awareness of what else is bidding locally that will cause contractors to pick and choose what to bid. I have seen bids delayed so as not to overlap with a larger project bidding in the region, which is smart. I have also seen cases where a bid is due just before a board meeting to approve the winning bidder, so there is no room to delay the bid for scope clarifications or to allow contactors more time to prepare, so bidders drop out. This happens so many times. An engineer spends a year or more pulling the spec together then allows 4-5 weeks for contractors to get a bid together and there is no flex in the bidding schedule to give contractors a few more weeks. Not smart!

 While recent years have made this situation worse with supply chain delays and a shortage of contractors to bid projects, unqualified contractors winning water treatment projects has been going on for years and is not a symptom of the pandemic. Engineers and owners need to put more thought into  the bidding process to ensure they get a competent contractor which will ensure a much more successful and harmonious project for all involved!

IDA 2022 World Congress a Global Meeting of Desal Minds

After changes of venue and multiple delays due to the Covid pandemic, the 2022 International Desalination Association (IDA) World Congress was finally held in Sydney Australia, October 9-13. It is the first time I have been to this conference, or any truly international water conference for that matter, and it was exciting and inspirational to see the global networking and established relationships across continents and the open sharing of technical knowledge and experiences. Everyone was drawn together by a common interest in water treatment, mostly by desalination, and protecting the earth’s most natural resource, no matter the country, language or culture. I may sound a bit cliché, but I was truly moved by the spirit and sense of common cause of the conference.

What’s New is the World of Desal? Brine Mining!

The main focus of the technical program was seawater desalination but there were some interesting topics and new developments being discussed in the desal world. Most notable to me was how to handle waste concentrate and a lot of interest in brine mining. Highly concentrated brine is being seen as a potential resource for rare earth metals, including lithium. First there needs to be processes to concentrate brine higher than conventional seawater membranes and companies such as Gradient and Toyobo presented on osmotically assisted RO (OARO) processes that can concentrate brine from a seawater process up to 130,000 mg/L TDS without needing significantly higher pressures. Osmotic assistance is provided by applying a saline stream on the permeate side, which lowers the osmotic pressure difference across the membrane, allowing permeate production at feed pressures less than the osmotic pressure of the feed. There is also interest in ultra-high pressure membranes and housings for achieving higher seawater recoveries and therefore higher brine concentrations, but I think if the counterflow processes are feasible, they are a safer and probably lower energy option.

 Once you have the highly concentrated brine, you have to extract the valuable constituents and from one presentation I saw from Dr. Monsalvo from Aqualia, that involves a lot of treatment steps… So it looks to me the recovered metals would need to be very valuable to offset the high cost of extraction. With world shortages in these elements, I’m sure with continued research the extraction costs will go down making these processes more feasible. There is no shortage of research in this area! There were also many presentations looking at minimizing the environmental impact of brines, indicating the industry realizes this needs to be addressed to ensure desalination is a viable water supply solution into the future.

Wastewater reuse also had a prominent share of the program, recognizing the role of desalination in reuse applications, with several dedicated sessions and two panel discussions, one of which I was very pleased to participate on.

The IDA Water Reuse Panel I was excited to be part of

I was also very impressed with how the technical sessions and panels were all conducted in the exhibit hall in walled-off areas, so it was easy to jump from session to session or to a panel discussion without leaving the hall. Meals were also served in the same area keeping attendees together all day. This is a great model for other conferences if it is logistically possible.

I can’t say I have anything negative to say about the show. Very professional production, great technical content, great networking, awesome venue! As long as you were able to get to Sydney… 

The comments and opinions in this post are my own and not those of my employer.

Manganese Removal Ain’t Manganese Removal!

 

I was looking at specifications for a project earlier this year that had very tight targets for iron and manganese (combined target of >0.06 mg/L) but there was no pilot data to back up that these targets were achievable. Bidders were required to guarantee these limits would be met by the specified pressure filter system with Greensand Plus media. When there was pushback in guaranteeing the performance of the system (that the engineer had designed) without any prior testing to show this was achievable, the response from the engineer was that there were other Greensand Plus filters in the State that were achieving these levels so there should be no issues making the performance guarantee…

This was essentially saying that the performance of a treatment process on one water source should be expected on a totally different source water without considering the water quality of the two sources. Anyone who knows anything about water treatment knows while iron is relatively easy to remove, manganese is a totally different animal. While manganese may be easy to remove on one water source, it could be very difficult to remove on another.

 In Chapter 3 of the AWWA ‘Iron and Manganese Removal Handbook, Second Edition’ the following statements are made:

• Oxidation of Fe and Mn: Manganese Dioxide (manganese in the oxidized form) forms a far finer floc (than ferric hydroxide), so fine at times that a granular media filter will not remove it.
• Organic Complexing of Fe and Mn: Operators experiencing difficulty in removing Fe and Mn (especially Mn) have uncovered some common factors:

o   A level of organic carbon (TOC) over 2 mg/L

o   Some level of ammonia or hydrogen sulfide in the feed water

• Adsorption Removal Methods (my summary): Manganese is best removed by adsorption on a manganese dioxide media like Greensand Plus or Pyrolusite. Iron is best removed by precipitation/filtration because iron adsorption blinds the media. Therefore, when both are present, the best process used is a combination of iron oxidation/filtration and manganese adsorption.

Further to the last point, oxidation of manganese takes a much longer time than iron where you are looking at from seconds to a minute for iron (Chapter 5, Chlorination) and up to up to 30 minutes or longer for manganese. Therefore in a filter system where an oxidant is dosed in the feed piping to the filters you can have adequate time in the piping and space in the filters above the media for iron oxidation (a few minutes) while allowing adsorption removal of the manganese.

There was also a very good article in AWWA’s Opflow in December 2021 titled “Evaluate and Optimize Manganese Treatment”. This article explains that the form and levels of manganese can vary considerably between wells. All manganese removal methods described in this article are based on sorption to the filter media. Therefore conditions must be optimized for the sorption mechanism on manganese oxide coated media including ensuring there is a free oxidant residual to provide a continuously regenerated adsorptive surface. The pH also impacts the Mn reaction kinetics with pHs above 7.0 more favorable.

As mentioned above, TOC, ammonia and H2S create a chlorine demand which impacts the chlorine available to oxidize the Fe and regenerate the filter media for Mn adsorption. Because the iron oxidation reaction is a lot faster compared to TOC, you typically get iron oxidation in the presence of TOC, as long as the iron is not organically bound to the TOC. When ammonia and H2S are present you may need a higher chlorine dose to overcome the demand from these compounds and provide sufficient iron oxidation. While you are not trying to remove manganese by oxidation/filtration, you still need a free oxidant residual to keep the manganese dioxide media regenerated so that is adsorbs the manganese. Therefore, a water with a high chlorine demand can impact the ability of the media to adsorb manganese. If ammonia is present, potassium permanganate may be a good option rather than chlorine as the oxidant because it does not react with the ammonia.

If iron and/or manganese is complexed with organics, the oxidation process can be significantly impacted. At a minimum, a higher oxidation dose and longer oxidation time will be required and if this works you could still create another problem with the formation of disinfection byproducts. Coagulation may be a better option to remove organically bound manganese and possibly iron also.

So clearly, iron and particularly manganese removal chemistry is not simple, and you can’t assume if the Fe and Mn levels on one water source are similar to another water source that a particular treatment technology will work equally on both. Other constituents in the water source impact removal performance and must be taken into consideration and ideally bench and/or pilot testing should be conducted to confirm the effectiveness of a proposed treatment process. To steal a saying from an old Mobile oil commercial, Manganese Removal Ain’t Manganese Removal!

The comments and opinions in this post are my own and not those of my employer.