Pile Filter Cloth Performance Data
Measured separation efficiencies, effluent values, cycle lengths and backwash rates for three pile cloth constructions across four loading conditions — trial results, not calculated examples.
Test Setup and Methodology
The data come from in-house loading trials on a pile cloth filter fed with secondary clarifier effluent. To establish defined loading conditions, biological sludge from the activation tank was dosed into the influent. This makes it possible to reproduce load peaks that occur only rarely and uncontrolled in normal operation.
TSS was determined according to normative standard using glass fibre filter papers with 0.5 µm particle retention. All values in the tables are measured results for the respective test point — they are not guaranteed values. Achievable performance on a specific plant depends on sludge characteristics, upstream treatment, coagulant dosing and plant hydraulics.
Staple fibre pile cloth
Spun staple fibre pile with a high fibre count per unit area. Builds a dense filtration matrix quickly and holds a stable separation efficiency even when the solids loading rate rises sharply.
| Loading mode | TSS inlet (mg/l) | Filtration speed (m/h) | Solids loading rate (g/m²·h) | TSS effluent (mg/l) | Separation efficiency (%) | Cycle length (s) | Backwash rate (% of inflow) |
|---|---|---|---|---|---|---|---|
| Low load | 24.75 | 7.38 | 183 | 1.73 | 93 | 648 | 3.6 |
| Normal load | 41.5 | 9.84 | 408 | 3.1 | 92.5 | 310 | 5.1 |
| High load | 76.7 | 9.69 | 743 | 3.8 | 95 | 175 | 7.83 |
| Extreme load | 245 | 5.97 | 1465 | 12 | 95 | 95 | 20 |
Multifilament pile cloth
Continuous multifilament yarn pile. Smooth filament surfaces release captured solids readily during suction cleaning, which keeps the separation efficiency rising with increasing load.
| Loading mode | TSS inlet (mg/l) | Filtration speed (m/h) | Solids loading rate (g/m²·h) | TSS effluent (mg/l) | Separation efficiency (%) | Cycle length (s) | Backwash rate (% of inflow) |
|---|---|---|---|---|---|---|---|
| Low load | 16.3 | 9 | 147 | 2.3 | 86 | 569 | 3.46 |
| Normal load | 51.7 | 9 | 466 | 2.1 | 96 | 240 | 7.04 |
| High load | 68 | 8.8 | 599 | 2.4 | 96.4 | 162 | 8.37 |
| Extreme load | 88 | 9 | 793 | 2.3 | 97.3 | 90 | 14.5 |
Microfibre pile cloth
Fine microfibre pile, densely installed on the woven support fabric. Delivers the lowest effluent TSS values of the three constructions — down to 0.53 mg/l under low load — at the cost of shorter filtration cycles.
| Loading mode | TSS inlet (mg/l) | Filtration speed (m/h) | Solids loading rate (g/m²·h) | TSS effluent (mg/l) | Separation efficiency (%) | Cycle length (s) | Backwash rate (% of inflow) |
|---|---|---|---|---|---|---|---|
| Low load | 12.6 | 9.69 | 121 | 0.53 | 95.8 | 398 | 4.3 |
| Normal load | 18 | 9.57 | 172 | 1.4 | 92.2 | 234 | 6.59 |
| High load | 38.7 | 9.69 | 375 | 1.45 | 96.2 | 108 | 11.39 |
| Extreme load | 54.5 | 8.46 | 461 | 2 | 96.3 | 90 | 14.4 |
What the Data Mean for System Design
The key finding is load resilience: with the staple fibre construction the solids loading rate rises from 183 to 1,465 g/m²·h — a factor of eight — while separation efficiency stays between 93 and 95 percent. The multifilament construction actually improves under load, from 86 to 97.3 percent, because the accumulating cake itself becomes part of the filtration layer.
The second finding is the trade-off between fineness and rinse water. The microfibre construction reaches 0.53 mg/l — the lowest effluent value of all test points — but its cycle length drops from 398 to 90 seconds and the backwash rate rises from 4.3 to 14.4 percent of the inflow volume. Anyone designing for the lowest effluent values must size the rinse water return accordingly, otherwise backwash water, not filter area, becomes the plant bottleneck.
In practice this means media selection is not purely a question of fineness but a balance between target effluent value, available filter area and the rinse water volume the plant can handle. This is exactly the trade-off we work through with operators and designers using these data.
The Metrics Explained
TSS inlet / effluent
Total suspended solids upstream and downstream of the filter. The effluent value is what discharge consents are written against, and it governs the removal of particulate-bound phosphorus.
Filtration speed
Hydraulic surface loading in metres per hour, referred to the submerged filter area. It determines how much filter area a given throughput requires.
Solids loading rate
Solids mass fed per square metre of filter area per hour. This figure — not the TSS concentration alone — governs how quickly the filter cake builds up.
Separation efficiency
Percentage TSS retention across the filter. With the finer constructions it stays stable or even increases as the load rises sharply.
Cycle length
Time between two suction cleaning events at constant load. Short cycles mean more frequent cleaning and therefore more rinse water.
Backwash rate
Rinse water volume as a percentage of the inflow volume. This figure is frequently underestimated at design stage and becomes the limiting factor for fine media under high load.
We name no plants, operators, customers, suppliers or manufacturers in connection with the trials shown here. The data are published in deliberately anonymised form and describe only the behaviour of the filter media.
Design With Real Data
Planning a tertiary stage, a retrofit or a media change? We work your load case through with these data and recommend the right construction — with a field test at your plant if required.