industrial holidays Anaerobic Wastewater Treatment in Industries
The effect of industrial holidays on ETP health

The ecosystem of industries is complex as well as consistent. However, shutdowns due to festivals, season, operational failure, or force give a halt to the whole system. Although mostly planned, these industrial holidays are intended to give relief, but deep down in the concrete basins of effluent treatment plants brews a storm of crisis, whether it may be in the primary, secondary, or tertiary systems.

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And if we focus on the secondary system, the microbial population gets the worst hit. This blog focuses on what happens inside the secondary system during an industrial holidays, its effects, precautions, and prevention.

The living Microbial world of ETP:

The secondary system is like a society where microbial populations i.e, bacteria, fungi, yeast, metazoans etc. thrive on:

Food: Readily biodegradable organic matter.

Shelter: Biofilms, flocs, or suspended habitats.

Environmental Comfort: pH, temperature, DO, and nutrients in a narrow optimal range.

Maintaining microbial diversity and stability is crucial for consistent ETP performance.

Microbial Starvation- A Hidden Shutdown Crisis

A 10-15 day shutdown without influent feed creates what we call a starvation phase in the bioreactor. The period can trigger several microbial stress responses:

Autolysis Begins:
  • Without food, heterotrophic bacteria begin digesting their own cellular reserves.
  • When reserves run out, cell walls rupture, releasing intracellular enzymes and ammonia into the mixed liquor.
Shift in Community Structure:
  • Fast-growing, high-COD degraders die off first.
  • Resilient microbes like filamentous bacteria and nitrifiers may survive longer, but their metabolic activity drops drastically.
Dissolved Oxygen (DO) Becomes Redundant:


  • With no substrate to oxidize, aeration continues but becomes wasteful.
  • High DO levels can paradoxically stress certain facultative anaerobes used to fluctuating oxygen levels.


MLSS/MLVSS Decline:
  • The Mixed Liquor Volatile Suspended Solids (MLVSS)- the biologically active portion of MLSS drops due to decay.
  • Settling characteristics deteriorate, and the SVI (Sludge Volume Index) can spike due to deflocculation.
Recovery is Not Instant – The Myth of “Rest and Run”

When production resumes, many assume the ETP will bounce back like a machine switched on. But biological wastewater treatment systems have no reset button.

Lag Phase in COD Reduction
  • Microbial populations take time to rebuild numbers and enzyme systems.
  • Expect 2-5 days of poor performance and higher COD/BOD in the outlet, especially in systems with no pre-seeding plan.
Sludge Age Misbalance
  • Sludge that has aged during the shutdown may have lost its settling efficiency.
  • Decayed sludge may also release toxins and nutrients, creating internal loading.
Shock Loads on Restart
  • Sudden reintroduction of full-strength effluent can lead to shock loading.
  • This exacerbates foaming, odor, and even system upset.
Preventive Measures

ETP health during shutdowns doesn’t have to be a gamble. Here are proven strategies, drawn from both research and field practices.

1.Feed Synthetic System:
  • Use glucose, molasses, milk whey, or diluted Urea/COD substitutes to mimic organic load at low levels (10-20% of actual COD).
  • Feed once or twice daily to maintain microbial respiration and floc integrity.\
2.Aerate intermittently:
  • Continuous aeration is wasteful. Instead, apply 4-6 hours/day intermittent aeration to maintain DO and prevent anoxic.
3.Monitor pH and ORP
  • During starvation, microbial metabolism can skew pH or ORP. Keep these in range to avoid unfavorable drift.
4.Bioaugmentation on Restart
  • Introduce high-count commercial biocultures tailored to your effluent type. This accelerates recovery.
  • Use starter cultures or preserved sludge from pre-holiday if available.
5.Sludge Management 
  • Remove aged or decaying sludge before shutdown. 
  • During long holidays, periodic recirculation or RAS/WAS adjustments prevent septic conditions.
Conclusion:

Industrial holidays are an unavoidable part of operations across industries such as textiles, pharmaceuticals, and chemicals and can’t be avoided but the problems related to it in an ETP can surely be avoided by taking the right steps, proper planning, and taking proactive measures.Investing in bioaugmentation, sludge handling, and strategic aeration ensures microbial resilience during shutdowns.

Team One Biotech is one of the leading Biotech Companies in India, providing advanced microbial solutions like bacteria for ETP treatment and bacteria culture for wastewater treatment.
📩 Reach out now to enhance your wastewater treatment efficiency.

📧 Email: sales@teamonebiotech.com

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