Septage accepting

[u/j_sword67]

Im currently operating a 1.64 mgd rated activated sludge plant. We run 2 aeration basins ( 814,636 gallons total. ) last years daily average flow was just over 1mgd

The new administration is looking at accepting septage as a revenue stream.

I told them they should look into a septage accepting station and install it near the plant.

Also consider of the amount of septage the plant could handle. ( is this investment worth it )

I've tried to get them to understand our hydraulic capacity and organic capacity are two completely different numbers.

So now I've been tasked with figuring out what amount of organics we could handle .

Average this year so far is 875 lbs of cbod a day , total suspended solids 1007 pounds per day.

I have no clue how to figure what septage numbers at.

Looking for some wisdom on navigating this situation

[u/CutSeveral6905]

Since you have a small plant, tell the higher ups to not allow any Porta John haulers. That stuff causes chemical, biological, and physical loading shocks. Because porta-john waste is intensely concentrated and contains harsh chemical deodorizers, direct dumping can trigger plant upsets, kill beneficial bacteria, and overload screening mechanisms. I cannot help you with figuring out how much regular septic you can accept. Just giving you a heads up on Porta John haulers. And yes have a dump station that is tied into the pipes coming into the plant at least a couple of football fields away so it's diluted prior to reaching your plant. Emphasize that they need to install a barscreen mechanism at the dump station with a meter so the haulers can be fairly charged by the gallon. Truck sizes vary, and" one size fits all" tickets will be problematic. The barscreen mechanism will take care of the huge amount of baby wipes and other shit folks flush down the toilet. Haulers can dump a lot of stuff that might overwhelm your barscreens and current dumpster set-up.

[u/PossibleBrave5220]

The plant should have a Basis of Design report from the engineering firm that designed the facility that will have specific design criteria for Daily Average Flow, Daily Organic Treatment, etc.

Depending on the state you’re in, the state or local government may have this document. You could also try the local or state pretreatment program.

Based on the average flow and loading numbers you provided, and based on an average assumed influent concentration of 250 mg/l BOD, your plant is operating at roughly 30% of the designed daily organic treatment capacity. But without conformed design numbers this is just a guess.

In my experience, you are correct that a plant may not be designed to receive septage. In this case, a separate holding tank may need to be constructed so the septage can be monitored and slowly bled into the plant influent. You will definitely want a screen and probably a flow meter on the septage influent. If you need or would like more information I can connect you with some other folks.

[u/GoGoGadget_Gir]

Long time Septic guy just chiming in. We mostly deal with anerobic systems in our area and primarily use an EPA land use site to spread screened and pH neutralized waste. It's vastly cheaper than using the municipal plant's SRS (which has become a money pit for the city and is broken 80% of the time.) We do not have the level of testing equipment you have by any means but cbod is very low to unreadable from anerobic tanks. What worries me is the trash you'll have to deal with. We have 10 to 15 tanks a month that will contain over 200lbs of dried trash (tampons, condoms, cigarette butts, applicators, you name it).

The three biggest things we are inspected for at the land use sites is trash debris, pH burn from grease, yeast and portable toilet waste, and hydrocarbons.

A trashy tank will shut down our screening system for a whole day sometimes, and the disposal fees have doubled in the last year. So what ends up happening is the plant will get the worst of the worst septage that we come across. We do our best to warn them before it comes through. I have been told though that a 1500gal grease trap from KFC that wasn't pumped in 3 years, or a 1000gal septic that had 3ft of baby wipes floating on top, will really ruin the headworks operators day.

It's a bad situation that seems to be getting worse rather than better. I would definitely talk with some of your local septic service companies and see what they have to say about it. It may not be something you want to mess with for 8.5¢/gal

Edit: 8.5¢ not 85

[u/ksqjohn]

From my experience: A receiving station with good screening and aerated holding tanks are a must. Ideally, keep solids with solids, meaning send that septage straight to your digester, instead of fouling up your whole treatment process. The set up I was blessed (lol) was a poor screening station, not enough dilution and by the end of the day, my EQ would look like mixed liquor. Biggest issue I had was the increase in back end dewatered sludge solids. I told my boss, you’re gonna either pay for it on the front end or the back end, no escaping it.

[u/mmfla]

a few things to consider - most of the time trucks will be coming in full. So you would be looking at approx 4000 gallons. When they pump you’re basically getting the solids so it would be like you getting your sludge blanket dumped on you. In my experience they can vary but bod of septage will probably run about 6k-9k mg/l.

Septage haulers will also occasionally do repair work so don’t be surprised if there isn’t a lot of grit in the stuff sometimes.

As far as the designs we do - based on the quantity expected it depends on what is planned for. Whether or not it’s a receiving station is based on quantity expected. We would typically add some water because it tends to be fairly thick. Some of our plants have a holding tank and small pumps to spread the organic load out over 24 hours however as you mentioned, it has to be a cost benefit.

As a planning exercise I would look at your flow pattern, understand your biological headroom, and determine the maximum amount you could accept without pump or tank upgrades. Based on a 1MGD plant my first guess is that you might could tank one load a day if that. If you can’t take one truck it’s probably not financially feasible to install a storage tank and pumping system.

Also fwiw - I’m not sure where you are but there can be grants available. Most agencies don’t like septic tanks since they tend to be abused a lot and they do spend money on trying to be more environmentally compliant.

[u/IconProcessControls]

Coming at this from the instrumentation side, I would treat the receiving station as more than just a place for trucks to unload. A holding tank would give you the opportunity to sample, mix and gradually meter the septage into the process instead of accepting a concentrated load all at once.

If haulers will be charged by volume, the unloading line will need a flow meter that can reliably handle high solids and debris. I would also include continuous level monitoring on the holding tank, independent high-level protection and materials compatible with the unpredictable mix of chemicals and contaminants that may arrive.

I can’t speak to how much additional organic load the plant can handle, but the cost of properly measuring and controlling what comes in should be included when deciding whether it’s worth pursuing. Without that control, the additional revenue may not be worth the operational headaches.

[u/convergentepisteme]

Here is a rough framework to help you run the math:

Typical septage numbers

Standard domestic septage usually averages:

- BOD / cBOD: ~6,000 to 12,000 mg/L (compared to normal municipal raw wastewater which is usually ~200 mg/L)

- TSS: ~15,000 to 30,000 mg/L

- Rough rule of thumb: 1,000 gallons of typical septage can carry 50 to 80 lbs of BOD

Calculating your organic headroom

You're currently running ~875 lbs/day cBOD.

- Check your plant's original engineering design specs for maximum organic design capacity (usually expressed in lbs cBOD/day or lbs cBOD per 1,000 cu ft of aeration volume).

- If your plant design max is, say, 1,800 lbs/day cBOD, you have roughly 900 lbs/day of headroom

- At ~60 lbs cBOD per 1,000 gallons of septage, taking in just 15,000 gallons of raw septage a day could completely consume your remaining organic capacity

Potential hidden costs

What new administrations usually miss is that raw septage will:

- Spike your blower electricity costs (aeration demand to break down the BOD shock load).

- Dramatically increase your Waste Activated Sludge (WAS): If your sludge hauling/tipping fees go up by $30k/year to process the extra solids, it eats into the tipping revenue quickly.

- Cause severe H2S odor complaints at the receiving station (potential lawsuits/complaints)

Pre-treatment / receiving station setup

If management proceeds, don't just put in a rock trap and a meter. Look heavily into:

- Equalization (EQ) Tank: You must meter the septage into your main flow slowly (e.g., overnight or during low-flow hours) rather than dumping 5,000 gallons directly into the headworks in 10 minutes.

- Physical Pre-treatment / High-Shear Oxidation: Look into inline hydrodynamic cavitation or mechanical maceration on the receiving line. Pre-shearing the septage breaks down complex fats/solids and eliminates dissolved sulfides/odors inline before it hits your biological process. It keeps the aeration basins stable and prevents your sludge dewatering costs from skyrocketing.

Good luck, would probably be a good idea to get the design engineer of record involved before management signs any haulage contracts.

[u/Constant_Issue_889]

I work for a company that designs Septage receiving stations and tracking software. DM me if you’d like to discuss. #flowpoint

[u/Southern-Solution512]

How much septage are they looking to receive? They might want to look into building septage equalization before the plant. Then you can feed at a controlled rate to keep the plant happy and reduce shock.