Currently lime water is dosed for final water pH correction at a client's WTW.
This lime water system is unable to achieve the additional pH correction required to counteract a proposed fluoride dose and so sodium hydroxide dosing is required (and is struggling with achieving required pH at...
I am wanting to confirm the impact on pH of sodium bisulphite being added to water. To do so, I need to calculate the number of H ions liberated when sodium bisulphite (NaHSO3) is added to water. For example, I know for ferric chloride the reaction is
FeCl3+3H20 ⇌ Fe(OH)3+ 3H+ + 3Cl-
i.e. 3...
Has anyone experienced pH dropping across GAC filters? The filters have been installed alleviate problems with pesticide in drinking water. Since commissioning the filters, the pH has been dropping from 8.3 at the inlet to as low as pH7.2 at outlet.
One theory is development of a biological...
Hello,
I've been asked by a client about the possibility of cleaning RGF Calder nozzles which have been blocked with manganese deposits and whether it would be possible to clean these nozzles with a DWI "Acid" / Chemical on the market (Which is DWI approved) that could clean / remove / dissolve...
I've seen in a number of reports an equation to work out a theoretical ferric or alum dose for coagulation.
The formulas go something like this....
Alum Dose (as Al2(SO4)3.18H20) in mg/l = 17.8 + 0.295 x Colour (°H) + 5.41(pH - 7)
[Mean Turbidity + Mean Colour] x 0.08 x 2 x 3.6 = mg/l as...
I'm working on a WTW upgrade at the moment and would appreciate some advice. A new secondary treatment building is to be constructed with chemical storage tanks being located below ground level. One of the chemicals to be stored in these tanks is sodium hypochlorite. A concern has been raised...
A lot of guidance I've read for sludge production refers to highly turbid & highly coloured raw waters. What would people consider the limit above which a raw water source could be considered highly turbid or coloured. For colour, I was thinking over 100 Hazen but I've seen raw waters with...
The way I understand it now is that there can be a number of reasons why “carrier water” is used:
• to actually help carry along the water i.e. to make sure the dosed chemical achieves a certain velocity range e.g. so lime powder doesn’t come out of solution and block dosing lines
• to ensure...
Hello,
I've been asked for advise regarding the range of acceptable pipeline velocities for pumping sludge generated at a WTW. I've had an internet trawl and have been through the usual textbooks (MWH, Twort) to see whether I could find any details. Most specs give guidance for wastewater...
Hello all,
As part of a WTW upgrade, we're changing from chlorine gas to sodium hypochlorite. The sodium hypochlorite dosing requires carrier water to maintain velocity in the dosing lines. This carrier water is final water from the WTW and as such has been dosed with sodium hydroxide. At a...
I'm currently working on an upgrade to an existing water treatments. Part of the upgrade includes new chemical storage and dosing equipment. Sodium Hypochlorite and Orthophosphoric Acid are both to be dosed at the same point in the treatment train (this is currently the case and they are both...
I'm currently designing a set of GAC contactors for pesticides (MCPA) removal at an existing water treatment works and was hoping someone could provide me with their thoughts on the following
The water authority currently installs GAC contactors as standalone units between primary and secondary...
Hi Guys,
I'm working as process engineer on the design of a set of manganese rapid gravity filters at an existing WTW with upstream DAF & RGFs. I've been tasked with confirming likely headloss through these secondary filters so we can confirm hydraulics. The primary filtered water will be dosed...
I’m working on a project for a water company upgrading a UF/MF water treatment membrane treatment works. Currently hypo is dosed post membrane direct into the pipeline followed by pH correction through a limestone contactor.
As part of the upgrade, the hypo would be dosed into a static mixer...
A colleague has been working on a scheme whereby a lime dosing system at a water treatment works is being upgraded and a temporary caustic dosing kit has been installed while the lime system is out of action. It is a conventional treatment works where lime is dosed upstream with ferric for...
I'm working on a project where we'e moving an existing lime dose point downstream of a clean washwater tank (to prevent oxidation & precipitation of manganese in the tank).
Are there guidelines/recommendation for
(1) whether lime is dosed and pH is raised first or chlorine dosed first
(2) is...
I’m currently investigating manganese deposition in the air nozzles of a RGF. The process was flocculation/coagulation with ferric and lime-poly-superpulsators-chlorine-contact tanks-MSP & Lime Dosing-RGFs-Final chemical Dosing-clear water tank with the RGFS backwashed using chlorinated, pH...
Based on the Water Authority's design guideline, the water backwash flowrate during the combined water/air portion of the backwash regime is between 6 -12 m3/m2/h. The backwash flowrate during the water only portion is 21 m3/m2/h. Our mechanical engineer is finding it to diffiuclt to source a...
I'm currently working as a process engineer on the design of a new chemical dosing sytem at a water treatment works . The chemicals to be dosed are MSP, Sodium Hypochlorite and Sodium Carbonate.
The water authority's specifications stipulate that the velocities in dosing lines should be in the...
I'm currently involved in the upgrading of a coagulant dosing system and have seen conflicting guidelines regarding the use of carrier water for dilution of aluminium sulphate - some guidelines advise against diluting metal salts before mixing to prevent hydrolysis occurring too early & some...
