My pH values have been dropping over a few weeks, I've been adding hydrated lime to try to bring it back up but its not working. My influent pH has been in the mid to high 7's, the ox ditch has been  mid to low 5's, my effluent has been mid to low 6's. Is the warmer temps having an effect on the pH levels? My settling test went to extreamly fast 220/200 on some days and  200/170 on others, I've looked at the microscope and the bugs seem active. My trubidity  has been very good staying below 9 some days in the low 5's. DO has been steady at 1.03-1.24. My clarifier has a blanket of 4' and holding. COD's on influent 146 and on effluent 34. Can anyone help, If need more info I can provide.

Hi Eric ,


Stopping nitrification  will increase the NH3 levels in the secondary effluent is it correct ? in that case how do you achieve complete nitrification in this situation  where nitrification  is mandatory ? and the PH should also increase !  Can you light some more information on this issue .
regards

BB,
Can you please advise us of the following parameters:

• raw influent alkalinity
• final effluent alkalinity
• raw influent kjeldahl nitrogen or ammonium
• final effluent kjeldahl nitrogen or ammonium
• final effluent nitrate

With this info we can calculate how much alkalinity should be consumed through the process and be able to confirm if the influent has sufficient buffer capacity.

Cheers

BB,
The alkalinity figures - do you have them as CaCO3?

Can you have a guess at the effluent nitrate?

Have you ever calculated alk loss through a process before?  If not I can show you the calcs.

Cheers

I was going to let everyone know yesterday but I didn't get the chance to. Yes they are pH levels, I dont have an alkalinity test kit as of yet I just ordered one and should have it by next week. I only have a very little lab right now but when the new plant is finished being built (9/30/10) I will have a bigger and more up to date lab with all the testing equipment that I need, without having to be sertified by the state. I would except any help or information with my pH problem.

How do I or can I raise it to the levels needed?

My daily flows have been around 15,000 and on weekends it drops drasticly to 5000 - 8000  a day but the design for plant is 40,000 a day up to 70,000. The Nuc. plant is on 4-10's now for the summer months and I have to have raw brought in to keep flows up a little. I've been testing the pH on the raw being brought in and its been around 6.0 to 6.5. I have 2 clarifiers but only using 1.

My units are gpd, the second sentence, The treatment plant I operate is for a nuclear power plant and all domestic waste is pumped to the treatment plant. All emploies work a 4 day 10 hr. shift Mon. - Thur. and Fri. thru Sun. there are maybe 100 people instead of 1500 people.
As far as the figures, I wont be to get them to you for a about a week.

Sorry it took so long to get back to everyone but had to wait for testing equipment to arrive.
raw inf. alk. = 540 mg/l CaCo3
final eff. alk. = 80 mg/l CaCo3
raw amm. = 10 ppm
final amm. = 0 ppm
the final nitrate will have to send out to be tested
I hope the info. will help you help me.
Geoff, how is the job on the island going?

On another note: I'm getting a new treatment plant, it's a package plant built by Water Inc. out of Acwort Ga. should be up and running by the end of Sept. It will have 2-25,000 gal. trains consisting of 2 surge tanks @7,600 gal a sludge holding tank an aeration tank @ 36,450 gal and a clarifier @4,460 gal. and a Cl2 tank @1,077 gal. the whole process will be weather protected (enclosed by a building) so this winter wont be as bad with iceing as last winter.

At the flow rates you gave us, I would be adding close to 80 lbs of lime each day to increase the alkalinity and the pH.  It can become a bit tedious in a small system when adding chemical to balance the pH.  Good luck in the future with your new system when it arrives.

~Eric

I have been avidly watching this post, and now I feel I need to add my tuppence worth.  You first mentioned that over the past few weeks you have noticed the pH dropping.  Quite rightly nitrifying conditions have been pointed out and the knock on effects and counter measures required to re-balance the pH.  

This would suggest that under normal operating conditions nitrification is not required.  I would suggest that you start planning a strategy to reduce your sludge age (something that you have not mentioned). Once you bring the plant back out of nitrifying conditions you'll notice pH will not be an issue, and have the added bonus that  the oxygen demand will reduce along with your electric bill.

If I have got it wrong and nitrifying conditions are required, though your are hesitant in adding alkalinity (by way of lime), you will have to do it, problem solving is never done in half hearted measures.  Go on add the lime watch the pH and when it starts swing back up the scale you'll know that you have added the correct amount!

One other thing worth mentioning about your new plant, it will have been designed not only to cope with flows and loads coming in but to meet a specific final effluent standard.  I would find this out pronto. If you have to nitrify you'll have the same problem as you have now with the lack of alkalinity to counteract the pH shift.  Someone will have to add in the cost of the regular chemical addition to allow this to happen.  Also look at other chemical alternatives to lime addition (Geoff mentioned a few).  Each one has it's +/- points be it H&S, cost, practicality etc.  Better to find these out now and plan for what one would best suit your application and who ever pays the bills is up to speed on what it will cost.

One other point you mentioned you are concerned about the monthly sampling coming up.  I am guessing this is done by who ever regulates your plant.  Check out your license you may be in breach of it due to the low pH coming out the back end.....Go on add the lime you know it makes sense!!!!

I have been watching my sludge age and have been taking corrective actions towards it. I have been wasting more and watching my blanket in the clarifierand and the color in ox. ditch. The blanket has been holding at 4 - 5 ft.(would like to get it to 2-3 ft.) and the color in the ditch has been going a little darker by the day. I've been watching the DO also and its been bouncing around from 0.80 to 1.50 (recommended to be in between 1.0-2.0). I raise and lower the rotors to try and keep the DO in the range needed. I will start adding the lime and see what happens for the next few days.
I have the design calculations, with a MCRT of 47 day it will be sufficient for nitrification.

BB wrote on Jul 10^th, 2010, 7:20am:


The MLSS getting darker is of concern.  Too much MLSS most likely.  What is the sludge age of the ditch (ignore the MCRT calculation for a nitrifying plant) and approximatley what % of the ditch is aerobic?

Cheers

BB,
Hate to split hairs...it is actually ammonium because that is the form (NH4+) at typical wastewater pH, everyone calls it ammonia but what the heck, so I will too...

Can you clarify your typical ammonia figures in and out because your high influent alk should cope and buffer the pH.  I can only assume your ammonia is higher than the testing reveals.  Given the nature of your flows could it be sitting the upstream system and fermenting to produce ammonia for significant periods?  High loads of ammonia can be toxic to nitrifiers.

If you are not denitrifying much then that means you don't recover lost alkalinity.  Do you know the maths behind alkalinity loss and recovery through nitrification/denitrification?

The % of the ditch that is aerobic is determined purely by observation.  Run around the tank with a DO probe and plot where the DO is about say 0.5mg/L, and that is the aerobic zone (or close enough).

Eff.amm. for week is 0,0,0,5,0,2,0. had a little finger problem while I was typing.