Solving High TSS Challenges in Wastewater Treatment: Operator Strategies and Practical Fixes

Troubleshooting And Fixing High TSS In Wastewater Treatment Plants

Operator‑focused guide • Practical diagnostics, fast fixes, and prevention

Total Suspended Solids (TSS) issues often spike during hydraulic surges, filamentous bulking, poor settling, or chemical upsets. This guide gives operators a field‑ready framework to diagnose causes, implement quick wins, and lock in stable compliance.

Understanding TSS And Targets

Definition: TSS measures particulate matter suspended in water/effluent (biomass, inert solids, FOG, chemical floc).
Impact: Elevated TSS risks permit exceedance, turbidity complaints, UV fouling, and downstream solids deposition.
Goal: Stabilize solids capture in primary/secondary clarifiers and prevent washout from aeration and final settling.

Common Root Causes Of High TSS

Primary clarification

Hydraulic surges: Storms or morning peaks exceed overflow rates; short‑circuiting lifts effluent solids.
Mechanical: Skimmer/collector out of service; sludge blanket too deep or too thin; weir not level.
Chemical: Coagulant dose off‑target; pH/alkalinity incompatibility with floc formation.

Secondary (biological + final clarifiers)

Bulking/foaming: Filamentous organisms reduce settleability (high SVI); F/M, DO, and selector zones mis‑tuned.
Carryover: MLSS too high; RAS rates mismatched; sludge age and wasting not aligned with loading.
Hydraulics: High surface overflow rate, wind‑driven mixing, or short‑circuiting at launders.
Chemical: Polymer under‑ or over‑dosing; poor preparation or aging; charge mismatch.

Tertiary/filters & disinfection

Filter loading: Upstream TSS spikes overwhelm cloth/sand/DF membranes; backwash ineffective.
UV fouling: Elevated TSS raises transmittance issues and sleeve fouling, reducing dose.

Quick Diagnostics

Symptom	Likely cause	Fast check	Immediate action
Final effluent looks turbid/grey	Secondary carryover; high SVI; hydraulic surge	Settleometer 30‑min, SVI, MLSS, clarifier blanket	Increase RAS, reduce MLSS via wasting, lower aeration mixing, split flow across basins
Pin floc in effluent	Low sludge age or floc shear	Microscopy for floc integrity	Reduce air intensity, optimize F/M, stabilize wasting
Brown foam/“rafts” on aeration	Filamentous growth; low DO/selectors	Microscopy for filaments; DO profile	Raise DO, improve selectors, adjust RAS/MLSS targets
Primary effluent TSS high	Weir/collector issues; sludge blanket mis‑set	Blanket depth, weir level, scum removal	Skim scum, re‑level weirs, increase sludge draw
Filter DP rising fast	Upstream TSS surge; polymer mismatch	Jar tests; polymer prep/age	Optimize polymer dose, trigger backwash, throttle filter loading

Fast Fixes By Process Area

Primary clarifiers

Blanket control: Maintain steady sludge withdrawal to prevent resuspension; avoid over‑thick blankets.
Surface management: Keep skimmers active; remove scum/FOG before it breaks up and carries to secondary.
Hydraulic balance: Level weirs; distribute inflow across bays to reduce short‑circuiting.
Chemical assist: If permitted, run jar tests; fine‑tune coagulant/polymer to improve floc without overdosing.

Aeration basins

MLSS targets: Bring MLSS into the plant’s normal band; waste steadily rather than in large swings.
DO control: Maintain adequate DO; reduce excessive air that shears floc or strips CO2 excessively.
Selectorship: Ensure selector zones (anaerobic/anoxic) are mixing and fed properly to discourage filaments.
Mixing: Avoid over‑mixing that breaks floc; check broken diffusers or high‑shear zones.

Secondary clarifiers

RAS/flow: Increase RAS to pull solids off the surface; balance between basins to avoid one clarifier overloading.
Weirs/launders: Clean algae; ensure even distribution; add baffles where practical to reduce short‑circuiting.
Wind and storms: Use windbreaks/curtains if available; during storms, stagger starts and avoid peak spikes.
Polymer (if used): Dose at the right contact point; verify make‑down concentration and aging time.

Tertiary filtration

Loading rate: Reduce instantaneous loading by distributing flow and triggering backwash cycles earlier.
Prep quality: Check polymer solution age, mix energy, and water quality; poor prep ruins floc capture.
Ops hygiene: Keep strainers clean; verify valves actuate fully; inspect media/cloth condition.

Control Targets And Daily Routines

Control point	What to check	Operator routine
MLSS & sludge age	Consistency vs load; avoid sudden swings	Daily MLSS; adjust wasting in small increments
SVI/settleometer	Settleability trends; filament risk	Run settle tests; correlate with microscopy
DO profile	Zones in spec; avoid dead spots	Spot‑check DO across basins; tune air valves
Clarifier blankets	Stable blanket without overflow	Measure blanket depth; adjust RAS/draw
Weirs/launders	Clean, level, uniform flow	Weekly cleaning; verify elevation
Polymer/coagulant	Dose, prep, and charge match	Jar tests; check solution aging and dilution

Action Plans

First 24 Hours (Stabilize)

Confirm measurements: Grab TSS samples at primary effluent, secondary effluent, and final effluent; run settleometer/SVI.
Balance hydraulics: Distribute flow across parallel basins/clarifiers; avoid overloading a single path.
Tune RAS/wasting: Increase RAS temporarily to reduce surface solids; begin small, steady wasting to bring MLSS to target.
Reduce shear: Moderate aeration intensity; check for broken diffusers or excessive mixing.
Support filtration: If tertiary filters exist, trigger backwash and optimize polymer.

Next 7 Days (Prevent Recurrence)

Microscopy cadence: Identify filaments vs healthy floc; adjust selectors, DO, and F/M accordingly.
Weir and launder maintenance: Clean and level; add minor baffles if practical.
Process trending: Trend MLSS, SVI, RAS %, effluent TSS, and flow peaks; set alarms for rapid changes.
Chemical optimization: Run jar tests to lock in coagulant/polymer dose and prep; document SOP.
Storm readiness: Create surge playbook (split flows, stagger pumps, pre‑empt backwash).

Operator Notes And Practical Tips

Small changes: Fine‑tune wasting and air in small steps; big swings destabilize floc.
Data + eyes: Combine lab numbers with settleometer, blanket sight glass, and launder visuals.
Consistent RAS: Keep RAS steady; avoid frequent large RAS changes that upset clarifiers.
Prep matters: The “wrong” polymer prep will underperform regardless of dose—verify mixing and aging.
Parallel capacity: Use all available basins/clarifiers during peaks; don’t let one path carry the plant.

Frequently Asked Questions

Do I fix TSS with more air?
Not usually. Excess air can shear floc and worsen carryover. Aim for adequate DO, not maximum.

Is polymer a cure‑all?
Polymer can help capture solids but won’t fix bulking or poor hydraulics. Diagnose root cause first.

What’s the best quick test?
A settleometer and microscopy together: settle behavior + floc integrity tells you both hydraulics and biology.

Conclusion

Stable TSS comes from steady hydraulics, healthy floc, and disciplined controls. Diagnose quickly with settle tests and microscopy, tune RAS/wasting and aeration, and keep clarifiers clean and balanced. Lock improvements with routine trending and a storm‑surge playbook.

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