Reliable RO plant for high silica groundwater source
Reliable RO plant for high silica groundwater source
(OP)
We have several groundwater borewells with up to 42mg/l SiO2, total mineralisation of about 4000mg/l but not much iron or manganese to worry about. The water obviously has a tendency to 'scale'. Our existing Reverse Osmosis plant needs three people to look after it 24/7, was built cheap and fast and fails regularly. When it fails, the consumers use more detergent and push up the phosphorus in the final effluent to the detriment of the consent to discharge. I am looking for an automatic, packaged, plug and play, reliable, 'build like a brick' tried and tested RO plant that will work for 20 years, inform the control building when it fails and needs the absolute minimum of chemical addition and an annual inspection and parts replacement. We have plenty of water, could waste some for backwashing and need a production rate of 18000 gallons per day (we will probably use 6000 gallons per day (27 cubic meters). Can you recommend a manufacturer and or supply experience that could help us to do this. Where are the Mercedes Benz and Rolls Royce RO plants and do you have one we can talk about? Thanks.





RE: Reliable RO plant for high silica groundwater source
Regardless of design if you increase the concentrations of minerals retained too high they are going to scale out. More cross-flow can help sweep them downstream as solids, but unless that is in your final stage it is just adding to troubles downstream. The lower you can keep your concentration factors the better.
Does your set-up allow for individual sampling of the tubes of membranes to isolate any patterns to the fouling?
Your comments about consumers using detergent leads me to the conclusion we are considering domestic water usage, so how clean are you trying to go with it?
RE: Reliable RO plant for high silica groundwater source
You have to either go with clariflocculation or UF as a pretreatment for RO. 27 cu.m/day is rather small.
RE: Reliable RO plant for high silica groundwater source
If you buy from some of the smaller garage type organizations, then it is buyer beware.
You will get what you pay for.
RE: Reliable RO plant for high silica groundwater source
Contact Koch and talk to them about it.
Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng
www.waterhammer.bigblog.com.au
RE: Reliable RO plant for high silica groundwater source
Yes - the R/O and UF guys are going to "poo poo" this suggestion -
Dave/Aquatic Technologies
www.eoh2o.com
RE: Reliable RO plant for high silica groundwater source
RE: Reliable RO plant for high silica groundwater source
RO is not always the best method for demineralizing water in every case. Many municipalities with high silica and other high fouling/scaling water supplies have either replaced or added EDR to their RO systems. If you are interested, try contacting Ionics, Inc (USA). They have years of experience with EDR systems.
S. Bush
www.water-eg.com
RE: Reliable RO plant for high silica groundwater source
We are still looking for the golden filter!
RE: Reliable RO plant for high silica groundwater source
42 mg/l is pretty high for silica but all depends on the concentration ratio of the RO and its arrangment like shaman2 said. Silica solubility is around 100 mg/l at "usual" pHs (around 7-7.5). It is higher at low pHs and much higher at high pHs. It is indeed very difficult to remove like quark and stanier wrote.
I have experience in cleaning and running a RO plant with 70 mg/l SiO2, 2500 mg/l Sulfate and 1000 ppm CaCO3 Hardness. You can use several types of antiscalants, some can work up to 160 mg/l SiO2 in the concentrate others up to 200-220 mg/l. After this everything depends on follow up on the unit so to detect early scale precipitation as Silica is very hard to remove (You will need at least 20 hours cleaning the membranes in ph 11 solution+EDTA+dispersant to begin to remove something).
So to summarize :
- get a full water analysis with Ph taken on site. Do not forget to ask for Barium and Strontium as they combine with Sulfates.
- find a reliable supplier of membrane antiscalant who has some software to predict antiscalant performance
- let him do the calc with his software and the analysis
- Make him check with the membrane manufacturer software that the conditions he gives you (conversion ratio mainly) is OK with the hydraulics of the membrane plant.
- Get a normalization program from a main membrane manufacturer website and begin logging every day the required data from your RO (Pressure, conductivity, temp, etc..)
- As soon as you see a shift of 10 % in the normalized flowrate or salt passage it's time to clean the RO. You can see with your chemicals supplier or try to make your own washing solutions.
- Check if your cleaning procedure is OK by going on membrane manufacturers sites (or contact me if you need links).
For your information the plant I'm speaking of has 70 mg/l silica a little iron, Hardness is 1000 ppm CaCO3, TDS around 4000 ppm, sulfate is around 2500 mg/l. The customer cleans every 1-2 Months. Cleaning takes one full day (acid and caustic).Conversion ratio is 50%.
Flowrate is 50 m3/h @ 14°C
Membranes lasted 5 years.
Regards - DF Morvan
RE: Reliable RO plant for high silica groundwater source
Geoffrey D Stone FIMechE C.Eng;FIEust CP Eng
www.waterhammer.bigblog.com.au
RE: Reliable RO plant for high silica groundwater source
RE: Reliable RO plant for high silica groundwater source
S. Bush
www.water-eg.com