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Tertiäre Filtrationsstufe mit Rohrleitungen und klarem Ablaufwasser in einer Kläranlage

TSS Removal & Tertiary Filtration

Filtration technologies for achieving ultra-low suspended solids in effluent.

Tertiary filtration is the backbone of any advanced treatment scheme. It removes residual suspended solids (typically from 15-25 mg/L to < 5-10 mg/L), captures particulate-bound phosphorus, and protects downstream processes like UV disinfection or membrane systems. Disc filtration, deep-bed sand filtration, and cloth media filters are the most common technologies, selected based on footprint, flow rate, and target quality.

Key Numbers

0
mg/L
Typical tertiary TSS target
0
mg/L
Advanced filtration target
0.00
kWh/m³
Disc filter energy use
0%
%
TSS removal efficiency

Technology Comparison

Disc Filtration

high

Rotating disc filters with pile cloth or woven media. Gravity-fed, continuous operation.

Footprint: Very small
Energy: 0.01-0.03 kWh/m³
Advantages
  • Smallest footprint
  • Very low energy
  • Continuous operation
  • Easy to retrofit
Limitations
  • Limited to gravity feed
  • Media replacement
  • Not for high TSS loads

Cloth Media Filter

high

Travelling-bridge or fixed-panel cloth filters. Similar to disc filters in performance.

Footprint: Small
Energy: 0.02-0.05 kWh/m³
Advantages
  • Compact design
  • Low energy
  • Good for retrofit
  • Simple maintenance
Limitations
  • Media degradation
  • Limited headloss
  • Needs pre-screening

Continuous Sand Filter

high

Upflow sand filtration with continuous countercurrent sand washing.

Footprint: Medium
Energy: 0.03-0.08 kWh/m³
Advantages
  • Handles variable loads
  • Chemical dosing possible
  • No backwash interruption
  • Proven technology
Limitations
  • Larger footprint
  • Sand loss over time
  • Reject water stream
  • Higher than disc filters

Membrane Filtration (MF/UF)

medium

Absolute barrier filtration with microfiltration or ultrafiltration membranes.

Footprint: Small
Energy: 0.1-0.4 kWh/m³
Advantages
  • TSS < 1 mg/L guaranteed
  • Pathogen barrier
  • Enables water reuse
  • Consistent quality
Limitations
  • Higher CAPEX and OPEX
  • Fouling management
  • Chemical cleaning
  • Higher energy demand

Engineering Insight: Filter Selection

For most municipal tertiary treatment applications, gravity-fed disc or cloth filters provide the best balance of performance, cost, and footprint. Reserve membrane filtration for water reuse applications or where absolute pathogen barriers are required.

For Existing Plants

Tertiary filtration is the most common add-on to existing plants. Disc filters can be installed in as little as 20 m² footprint for 10,000 m³/d capacity. Key design considerations: available hydraulic head (typically 0.5-1.5m needed), backwash water return to head of works, and chemical dosing point if P co-removal is required.

TSS Discharge Requirements

While the EU Directive does not set an explicit TSS limit for tertiary treatment, achieving nutrient limits (especially TP < 1.0 mg/L) inherently requires TSS < 10 mg/L. Many national permits set TSS ≤ 10 mg/L or ≤ 5 mg/L for tertiary effluent.

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Frequently Asked Questions

Related Content

Phosphorus Removal

Linked to particulate P capture

Nitrogen Removal

Retrofit Solutions

Tertiary Treatment Overview

Last reviewed: August 2026. Regulatory requirements may vary by national implementation. This content is for informational purposes and does not constitute legal or engineering advice.