How do I convert mg/L (milligrams per litre) to SG (specific gravity)

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Anonymous Poster	How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/13/2008 6:45 PM
	I am looking at a separations process - concrete wastewater filtration. We are entering the filter at 220 mg/l and exiting at 8 mg/l. How do I express 220 mg/l in terms of specific gravity?
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#1 "Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity)" by CSM Engineer on 02/13/2008 7:41 PM (score 5)
#6 "Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity)" by coconutpete on 02/14/2008 11:39 PM (score 2)

CSM Engineer Guru Join Date: Sep 2007 Location: Reno, NV (USA) Posts: 608 Good Answers: 66	#1 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/13/2008 7:41 PM
	I assume that the numbers you're using are solids loading. Since pure water is 1 g/cc or 1 kg/l, at 220 mg/l solids loading, a liter of your water should be 1.00022 kg. Specific gravity is the density of your material divided by the density of the reference material (pure water). So your S.G. is 1.00022 kg/l divided by 1 kg/l or 1.00022 (no units). The S.G. of your filtrate is 1.000008. Make sense? __________________ Aequam memento rebus in arduis servare mentem.
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JohnDG Guru Join Date: May 2006 Location: Reading, Berkshire, UK. Going under cover. Posts: 9684 Good Answers: 468	#2 In reply to #1 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/13/2008 7:52 PM
	~~BWT, Guest, - In brewing, these figures are often expressed without the decimal point, i.e. 1220 and 1008, when referring to the original gravity (OG) of a brew.~~ CSMEngineer - your edit has just bollixed up my comment! I took your figures for gospel without checking - my bad. __________________ "Love justice, you who rule the world" - Dante Alighieri
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CSM Engineer Guru Join Date: Sep 2007 Location: Reno, NV (USA) Posts: 608 Good Answers: 66	#4 In reply to #2 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/14/2008 11:01 AM
	Sorry, I realized about 10 min after I hit "post" that I was working in grams, not milligrams. I knew I'd really be drug through the rasher for that! __________________ Aequam memento rebus in arduis servare mentem.
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Anonymous Poster	#5 In reply to #1 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/14/2008 10:58 PM
	I did not even ask the question but the answer was great.
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user-deleted-1103 Active Contributor Join Date: Jun 2007 Location: Maryland, USA Posts: 20 Good Answers: 2	#9 In reply to #1 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/15/2008 11:12 AM
	I did the analysis and reached the same conclusion as CSM Engineer.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#3 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/14/2008 5:06 AM
	Any variation in settleable solids loading in a water stream at those levels is tiny in comparison with the SG of theoretically pure water (around 1,000,000mg/l - it does vary quite a bit with temperature!). So unless 6-figure accuracy is required, and it clearly isn't because the temperature isn't tied down in this post, then published figures for water density at the ambient temperature can be used with a high degree of confidence. So don't worry about it. As an aside, 220mg/l total dissolved solids is well within the World Health Organisation guidelines for drinking water, and no density correction is usually made at these figures. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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coconutpete Power-User Join Date: Feb 2007 Location: Suva Fiji Islands Posts: 229 Good Answers: 3	#6 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/14/2008 11:39 PM
	You Dont Specific Gravity relates to the density of a liquid your liquid is still water therefore the SG is the same 1. You have added setelable solids to the water. Therfore the water is still water as the solids are suspended in the water. The correct way of expressing what you have is. (The product is water containing 220mg/l of suspended solids) You could then define the solid and particle size if you want to. __________________ "Multa ferunt anni venientes commoda secum, Multa recedente adimiunt". (The years as they come bring many agreeable things with them; As they go they take many away).
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Paddler Power-User Join Date: May 2007 Location: Sweet home Alabama Posts: 144 Good Answers: 7	#7 In reply to #6 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/15/2008 8:24 AM
	Coconutpete is right. Trying to use S.G. to measure or define suspended solids will go no where good. An industry standard is as he describes. There are others but in the water treatment industry it is the most common. Don't confuse dissolved solids and dispersions with suspended solids. Good Post!!
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agua_doc Guru Join Date: Dec 2006 Location: Brecksville, OH Posts: 1621 Good Answers: 18	#8 In reply to #6 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/15/2008 10:34 AM
	Agreed! As coconutpete indicates, the settleable solids should be described separately from the water portion of the mixture. The weight of the solids in the suspension should be used to describe concentration of solids (wt%) in the mixture, while the water portion still has a specific gravity of 1.000 __________________ "Consensus Science got us into this mess, then why can't it get us out?" : Rephrase of Will Rogers Comment
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Abdel Halim Galala Guru Join Date: Feb 2007 Location: Cairo, Egypt Posts: 1733 Good Answers: 248	#10 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/16/2008 1:52 AM
	Specific Gravity = Density of Material / Density of Water Density of material = 220 mg/l = (220/1000) g/l = [220 / (1000x1000)] kg / [1/1000] m³ = 0.22 kg/m³ S.G. of solids = (0.22 kg/m³) / (1000 kg/m³) = 0.00022 __________________ It is better to be defeated on principles, than to win on lies!
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Anonymous Poster	#11 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/16/2008 5:02 AM
	Hi! Your filtration system does not arrest 8 mg/l. If you want your filtration system to be rated, you need to take into account the system for rating filter media like Beta ratio etc. Can you inform what type of application it is? If it is water filtration while breaking concrete to recirculate cooling water, then 8 mg/l going back is not much of a problem. Guest
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hughes838 Commentator Join Date: Feb 2008 Posts: 59	#12 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/16/2008 1:22 PM
	Specific gravity is the ratio of the density of any substance to the density of water (1000 kilograms per cubic meter, or one gram per cc). In your case it looks like you have a density going in of 1.22mg per cc, and coming out of 1.008mg per cc, therefore the SG would be 1.22 in and 1.008 out. Remember since all the units cancel you are dividing by one (density of water is 1g /cubic centimeter). Good luck! hughes838
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hughes838 Commentator Join Date: Feb 2008 Posts: 59	#13 In reply to #12 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/17/2008 3:52 PM
	What's a power of ten among friends? Sorry, I forgot that 1000mg = 1 gram (i.e. 220 mg of solids equal .22 of one ml (cc) of water). Therefore the density of your unfiltered sample is 1.00022g/lt and your final is 1.000008 g/lt (for SG you still divide by one (1), the density of water). Thanks Abdel Galala. hughes838
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JohnDG Guru Join Date: May 2006 Location: Reading, Berkshire, UK. Going under cover. Posts: 9684 Good Answers: 468	#14 In reply to #13 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/17/2008 4:51 PM
	One power of ten among friends: " '- here's the tenner I owe you.' 'Thanks, I thought it was only a quid! What are you drinking?'" Three powers of ten: " '- here's the tenner I owe you.' 'You'll come to some serious harm unless I get the other £9,990 by the weekend!'" __________________ "Love justice, you who rule the world" - Dante Alighieri
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JohnDG Guru Join Date: May 2006 Location: Reading, Berkshire, UK. Going under cover. Posts: 9684 Good Answers: 468	#15 In reply to #13 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/17/2008 4:58 PM
	Also, please see previous posts - the liquid (unless it contains dissolved substances) still has an S.G. of 1. This is liquid containing solids which can settle out. __________________ "Love justice, you who rule the world" - Dante Alighieri
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Bob B. Power-User Join Date: Feb 2006 Posts: 139	#16 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 02/18/2008 10:58 AM
	Are you referring to dissolved solids? Usually expressed in PPM (parts per million) which is same as mg/l.
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stoni11 Participant Join Date: Oct 2009 Location: Welkom in South Africa Posts: 1	#17 Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity) 10/23/2009 8:21 AM
	How do I convert SG (specific gravity) to mg/L (milligrams per litre)
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Good Answers:

These comments received enough positive votes to make them "good answers".

#1 "Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity)" by CSM Engineer on 02/13/2008 7:41 PM (score 5)
#6 "Re: How do I convert mg/L (milligrams per litre) to SG (specific gravity)" by coconutpete on 02/14/2008 11:39 PM (score 2)

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Users who posted comments:

Abdel Halim Galala (1); agua_doc (1); Anonymous Poster (2); Bob B. (1); coconutpete (1); CSM Engineer (2); hughes838 (2); JohnDG (3); Paddler (1); PWSlack (1); stoni11 (1); user-deleted-1103 (1)

You might be interested in: Density and Specific Gravity Instruments, Application Specific Integrated Circuits (ASIC), Ion Specific Electrode Meters

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