Waste water low outflow to river

[Traineespark]

Hi guys I’m new to this forum. I’m an electrician in a large food plant in Ireland. We’ve been having an extremely difficult time with out waste water treatment plant. It is a very large treatment plant but I’m unsure of the daily flows in/out.

It is an activated sludge plant and capable of high out volumes but we are only managing 6 l/s but want 14 l/s which we cannot achieve. We are happy that mechanically/electrically the plant is fine.

We think biologically it’s not right. We have very low mlss and because of this we have stopped making sludge for the foreseeable.

Our 2 membrane tanks are outputting low litres per second and what I would love to know; is there a direct correlation between low mlss and low output?

Our clean water is pumped through the membranes and the muck is sent to make sludge. Which is stopped at present.

If I’m not being clear let me know and I’ll try my best to clarify.

Thanks

 

[bimr]

With your description, there is no way to know what is going on,

With the activated sludge process, influent flow will basically be the same as the influent. The MLSS should be at least 1,500 - 2,000 to operate properly. Less than this level, the system will not function and will result in poor or untreated effluent. If you don't have enough influent or process waste, the activated sludge will also operate poorly.

You need to obtain all of the process parameters and the discharge permit, and talk to a wastewater enginer.

 

[Traineespark]

for our plant to run efficiently our mlss is around 6,800 to 7,200. it was brought down to around 2,000 to deal with the filamentous as per our engineers instructions, but the side effect - that we think - we have low output through the membranes to outfall. it now means that there is process related delays as we have to balance the water inflows as we are only getting 7/l sec outfall and we could normally get 14 l/s.

i suppose i just wondering is there calculations, or a rule of thumb, in relation to the mlss levels corresponding to the outflows. i wont start my course until September so im just trying to get a handle on whats going on

 

[bimr]

Bacterial flocs, extracellular polymeric substances (EPS), colloids, microsolutes, and macrosolutes are all present in the MLSS. Membrane systems function at substantially greater MLSS concentrations than activated sludge treatment systems. With the higher concentration of MLSS in membrane systems, membrane fouling may occur due to the high level of suspended particles. Several studies have shown that with higher MLSS concentrations, membrane permeability decreases.

The concentrations of both polysaccharides and proteins fractions of Extracellular polymeric substances (EPS) rise with increasing MLSS concentration. At each flux evaluated, an increase in MLSS results in a substantial drop in membrane permeability and an increase in fouling rate. Thus, when MLSS concentrations grow, so does membrane fouling.

Filamentous bulking can dramatically enhance the generation of soluble microbial products (SMP), which in turn significantly increases membrane fouling.

A non-ideal MLSS increases the risk for biological fouling. EPS, in particular, has the potential to pollute the membrane by:

- Cake forming, which is typical and may be cleaned with a backflush.

- Pore obstruction, i.e., the solids/eps obstructs water passage through pores.

- Biofilm formation, i.e., EPS enables biofilm adhesion to membranes, ultimately closing holes.

If your biomass contains more EPS (non-filamentous bulking, foaming filaments) and filaments that might strengthen biofilms on the membrane, your membrane maintenance will entail more cleaning cycles and an earlier replacement than in a system with better conditioned MLSS. As a result, even with an MBR system, it is critical to check EPS and filaments.

From your comments, it appears that the membranes are fouled since the membranes will not pass the rated throughput. I would suggest that you need to have a process expert from whoever you purchased the system evaluate the operation.