Q: Which data do you need to size a plant?

As a minimum: flow rate (average and peak, m³/h), inlet concentration of the target parameter (TSS, COD, FOG, total phosphorus), the required effluent value, temperature and pH. For sludge applications we also need sludge type (primary, WAS, digested, chemical), dry solids content and daily sludge production. A flow diagram and a laboratory analysis speed up the process considerably.

Q: What is the difference between primary, secondary and tertiary treatment?

Primary treatment removes settleable and floatable material physically (screens, sedimentation, flotation). Secondary treatment is the biological stage that degrades dissolved organics (activated sludge, MBBR, biofilm processes). Tertiary treatment is the polishing stage after biology — filtration, phosphorus removal, disinfection — and is where cloth filtration is normally installed.

Q: Can I use your plant finder instead of sending an enquiry?

The plant finder gives you a technology recommendation based on your treatment goal, flow rate and load in a few clicks. It is a pre-selection tool, not a design. Use it to narrow down the options, then send the result to us — the parameters you entered are transmitted with the enquiry so we can respond with a concrete proposal.

Q: How much space does a treatment stage need?

Footprints are technology-dependent. A 25 m³/h DAF unit occupies roughly 5.0 × 1.5 m, a screw press for medium sludge loads about 2.5–4 m in length. Pile cloth media filters are the most compact tertiary option because filtration is vertical rather than horizontal. Exact dimensions are given in the technical data table of each product page.

Q: What are pile cloth media filters and what are their advantages?

Pile cloth media disc filters use textile filter discs with a pile surface. Water flows from outside in, solids are retained on the pile, and a vacuum backwash cleans the cloth segment by segment while filtration continues. Advantages: compact footprint, very low energy consumption, low TSS in the effluent, no filter bed to fluidise, and retrofit into existing basins is possible.

Q: What TSS values are achievable with cloth filtration?

With a 10 micron pile cloth, effluent values in the range of 5–10 mg/L TSS are typical. With 5 micron pile cloth and good flocculation, values below 5 mg/L are achievable. The decisive design input is not the concentration alone but the TSS load at the filter inlet in g/m²·h.

Q: Which phosphorus effluent values are achievable?

Combined with chemical precipitation upstream, total phosphorus values below 0.1 mg/L are achievable in practice with 5 micron pile cloth media. The value we can guarantee depends on the raw water, the precipitant and the contact time, and is defined project by project.

Q: When do I choose 5 micron and when 10 micron pile cloth?

Use 10 micron for general tertiary polishing and higher solids loads — up to about 700 g TSS/m²·h and roughly 70 mg/L at the inlet. Use 5 micron where phosphorus polishing or very low TSS is the target; the trade-off is a lower permissible solids load of about 250 g/m²·h and a maximum inlet of about 30 mg/L.

Q: Vertical or horizontal disc filter — which one?

Vertical disc filters (RF-VCF) are the standard for tanks with limited plan area and are the most common tertiary configuration. Horizontal disc filters (RF-HCF) put more filter area into a low-headroom building or into an existing shallow channel. Hydraulic capacity per disc is the same; the choice is driven by the geometry of the space you have.

Question 1

How do I choose between DAF, lamella clarifier and cloth filtration?

Accepted Answer

It depends on what you need to remove and at what load. Dissolved air flotation is the right choice for low-density solids, fats, oils and emulsions, typically upstream in the process. A lamella clarifier removes well-flocculating, settleable solids at high hydraulic load in a small footprint. Pile cloth media filtration is a polishing stage: it takes an already low TSS concentration (typically < 30–70 mg/L) down to single-digit values. In many plants two of these stages are combined rather than one replacing the other.

Question 2

Which data do you need to size a plant?

Accepted Answer

As a minimum: flow rate (average and peak, m³/h), inlet concentration of the target parameter (TSS, COD, FOG, total phosphorus), the required effluent value, temperature and pH. For sludge applications we also need sludge type (primary, WAS, digested, chemical), dry solids content and daily sludge production. A flow diagram and a laboratory analysis speed up the process considerably.

Question 3

What is the difference between primary, secondary and tertiary treatment?

Accepted Answer

Primary treatment removes settleable and floatable material physically (screens, sedimentation, flotation). Secondary treatment is the biological stage that degrades dissolved organics (activated sludge, MBBR, biofilm processes). Tertiary treatment is the polishing stage after biology — filtration, phosphorus removal, disinfection — and is where cloth filtration is normally installed.

Question 4

Can I use your plant finder instead of sending an enquiry?

Accepted Answer

The plant finder gives you a technology recommendation based on your treatment goal, flow rate and load in a few clicks. It is a pre-selection tool, not a design. Use it to narrow down the options, then send the result to us — the parameters you entered are transmitted with the enquiry so we can respond with a concrete proposal.

Question 5

How much space does a treatment stage need?

Accepted Answer

Footprints are technology-dependent. A 25 m³/h DAF unit occupies roughly 5.0 × 1.5 m, a screw press for medium sludge loads about 2.5–4 m in length. Pile cloth media filters are the most compact tertiary option because filtration is vertical rather than horizontal. Exact dimensions are given in the technical data table of each product page.

Question 6

What are pile cloth media filters and what are their advantages?

Accepted Answer

Pile cloth media disc filters use textile filter discs with a pile surface. Water flows from outside in, solids are retained on the pile, and a vacuum backwash cleans the cloth segment by segment while filtration continues. Advantages: compact footprint, very low energy consumption, low TSS in the effluent, no filter bed to fluidise, and retrofit into existing basins is possible.

Question 7

What TSS values are achievable with cloth filtration?

Accepted Answer

With a 10 micron pile cloth, effluent values in the range of 5–10 mg/L TSS are typical. With 5 micron pile cloth and good flocculation, values below 5 mg/L are achievable. The decisive design input is not the concentration alone but the TSS load at the filter inlet in g/m²·h.

Question 8

Which phosphorus effluent values are achievable?

Accepted Answer

Combined with chemical precipitation upstream, total phosphorus values below 0.1 mg/L are achievable in practice with 5 micron pile cloth media. The value we can guarantee depends on the raw water, the precipitant and the contact time, and is defined project by project.

Question 9

When do I choose 5 micron and when 10 micron pile cloth?

Accepted Answer

Use 10 micron for general tertiary polishing and higher solids loads — up to about 700 g TSS/m²·h and roughly 70 mg/L at the inlet. Use 5 micron where phosphorus polishing or very low TSS is the target; the trade-off is a lower permissible solids load of about 250 g/m²·h and a maximum inlet of about 30 mg/L.

Question 10

Vertical or horizontal disc filter — which one?

Accepted Answer

Vertical disc filters (RF-VCF) are the standard for tanks with limited plan area and are the most common tertiary configuration. Horizontal disc filters (RF-HCF) put more filter area into a low-headroom building or into an existing shallow channel. Hydraulic capacity per disc is the same; the choice is driven by the geometry of the space you have.

Question 11

How often does the filter cloth have to be replaced?

Accepted Answer

Under normal municipal and industrial tertiary conditions the pile cloth reaches a service life of several years. Abrasive solids, fibres, oil and grease or aggressive chemistry shorten it. Cloth segments are replaced individually without dismantling the disc, so replacement is a maintenance task rather than a plant shutdown.

Question 12

Can cloth filters be retrofitted into existing treatment plants?

Accepted Answer

Yes — that is one of their main advantages. Cloth filters are frequently installed into existing secondary clarifier structures, into disused sand filter basins, or as a bypass polishing line. Because they filter continuously during backwash, no redundant second unit is needed for the backwash cycle.

Question 13

Does the filter keep working during backwash?

Accepted Answer

Yes. The vacuum backwash head cleans one segment at a time while the remaining filter area continues to filter. Backwash water demand is typically in the low single-digit percentage range of the throughput and is returned to the head of the plant.

Question 14

How does a screw press work?

Accepted Answer

A screw press dewaters sludge with a slowly rotating screw inside a screen basket or a stack of moving and fixed rings. Conditioned sludge is conveyed against an adjustable counter pressure plate, filtrate drains through the screen gaps and a dewatered cake leaves the press at the discharge end. The moving rings scrape the screen continuously, which is why the press needs very little wash water.

Question 15

Screw press or decanter centrifuge — which is better?

Accepted Answer

A decanter reaches a higher cake dryness on most sludges and handles very high throughput, but it consumes several times more energy, is noisy, wears faster and needs a machine hall. A screw press runs at a fraction of the energy, can be operated unattended 24/7, is quiet and much simpler to maintain, at a somewhat lower cake dryness. For small and medium plants the total cost of ownership usually favours the screw press. We have a detailed side-by-side comparison in the comparison section.

Question 16

How high is the energy consumption of a screw press?

Accepted Answer

Screw presses are among the lowest-energy dewatering technologies. Drive power for the RF-SP series is in the range of a few hundred watts to a few kilowatts depending on size, and the screw turns at roughly 0.2–1 rpm. Compared with a decanter of the same capacity the specific energy demand is typically an order of magnitude lower.

Question 17

What cake dryness can I expect?

Accepted Answer

It depends entirely on the sludge. Typical ranges with good polymer conditioning: waste activated sludge 15–20 % DS, mixed sludge 18–22 % DS, digested sludge 20–25 % DS, primary and chemical/physical sludge up to 30 % DS or more. Reliable figures come from a dewatering test with your own sludge — which is exactly what our rental and pilot units are for.

Question 18

How much polymer do I need?

Accepted Answer

As an orientation, 3–6 kg active polymer per tonne of dry solids for waste activated sludge, 2–4 kg/t DS for mixed sludge and 4–8 kg/t DS for digested sludge. The actual demand is determined in a jar test and depends strongly on sludge age and charge density. Our polymer demand calculator in the engineering hub gives you a first budget figure.

Question 19

Can a screw press run unattended?

Accepted Answer

Yes. The RF-SP series is designed for fully automatic 24/7 operation with automatic start-stop, integrated washing cycles and remote monitoring. The typical operating regime is unattended running with a short daily visual check.

Question 20

How do I calculate my sludge disposal cost saving?

Accepted Answer

Disposal is billed per tonne of wet cake, so cost scales inversely with dry solids content. Raising a cake from 15 % to 22 % DS reduces the disposal mass by roughly a third at the same dry solids load. The sludge and disposal cost calculator in the engineering hub does that calculation for your figures.

Question 21

What is a DAF unit and what is it used for?

Accepted Answer

DAF stands for dissolved air flotation. Water saturated with air under pressure is released into the flotation cell, forming micro bubbles of 20–50 µm that attach to flocculated solids, fats and oils and carry them to the surface where a skimmer removes them. DAF is the standard pre-treatment in food, beverage, dairy, slaughterhouse, chemical and metal processing wastewater.

Question 22

DAF or lamella clarifier?

Accepted Answer

Use DAF when the solids are lighter than water or close to neutral buoyancy — fats, oils, emulsions, fibres, algae, protein. Use a lamella clarifier when the solids settle well and you mainly need to remove hydraulic load in a small footprint at a lower operating cost. DAF has the higher separation efficiency on difficult matrices; the lamella clarifier has almost no moving parts and a lower energy demand.

Question 23

How much FOG and TSS removal does a DAF achieve?

Accepted Answer

With correct coagulation and flocculation, removal rates of 90–98 % for fats, oils and grease and 85–95 % for TSS are realistic on typical food industry wastewater. Removal falls sharply if the chemical conditioning is not matched to the wastewater, which is why we always look at the coagulant and polymer regime together with the machine.

Question 24

How are polymers prepared and dosed?

Accepted Answer

A polymer preparation unit dissolves powder, emulsion or liquid polymer fully automatically in a three-chamber system: wetting, maturing and storage. Correct maturation time is critical — under-matured polymer performs poorly regardless of the dose. The ready-to-use solution is then dosed proportionally to the sludge or water flow.

Question 25

Powder or emulsion polymer?

Accepted Answer

Powder polymer is significantly cheaper per kilogram of active substance and is the economical choice from moderate consumption upwards, but it needs a proper preparation unit and careful handling. Emulsion polymer is easier to handle and needs less equipment, but costs more per kilogram of active substance. The break-even is usually reached quickly in continuous operation.

Question 26

Do I need a separate flocculation stage?

Accepted Answer

Almost always, yes. Both flotation and lamella separation rely on a floc that is large and stable enough to be separated. A coagulation stage with fast mixing followed by a gentle flocculation stage is part of the standard scope of our DAF units.

Question 27

What is an MBBR and when is it the right choice?

Accepted Answer

A moving bed biofilm reactor holds free-floating plastic carriers in suspension; the biomass grows as a biofilm on the carrier surface. It is the right choice when you need to increase the capacity of an existing biological stage without building new tanks, when the load fluctuates strongly, or when you need a compact biological stage with no sludge return.

Question 28

How is an MBBR sized?

Accepted Answer

Sizing is based on surface load, not on volume load: the required carrier surface area follows from the daily BOD or ammonium load divided by the permissible surface load. Typical values are 5–15 g BOD/m²·d for carbon removal and 0.5–1.5 g NH₄-N/m²·d for nitrification, with a strong temperature dependency below 15 °C. The carrier fill ratio is usually 40–70 %. These are literature design ranges for orientation — the actual plant is sized from your measured load.

Question 29

MBBR or conventional activated sludge?

Accepted Answer

Activated sludge is the cheaper option per m³ where you have the tank volume and a stable load. MBBR wins where space is limited, where the load fluctuates or is seasonal, where you need to upgrade an existing plant, and where you want to avoid sludge bulking problems because the biomass is fixed on the carrier and not returned.

Question 30

Can I test a unit before buying?

Accepted Answer

Yes, and we strongly recommend it for sludge dewatering. We provide mobile rental units — skid-mounted or containerised — that run on your own wastewater or sludge under real conditions. This gives you measured cake dryness, polymer consumption and throughput instead of a datasheet estimate.

Question 31

What does a rental unit cost?

Accepted Answer

The rental rate depends on unit size, rental period and configuration. Rental fees are credited in full against a subsequent purchase of the same technology, so a trial period effectively becomes part of the investment. We quote individually — send us the application and duration and you get a figure.

Question 32

How quickly can a rental unit be delivered?

Accepted Answer

As a rule our rental units are operational within 5 to 10 working days from order, subject to availability. Delivery, mechanical and electrical connection support, commissioning and operator instruction are part of the package.

Question 33

When is renting better than buying?

Accepted Answer

Renting makes sense for a defined project duration, for peak load coverage, as a bridge while a permanent plant is being built, during a maintenance shutdown of your own machine, and as a technology trial before investing. If the requirement is permanent and the payback period is short, buying is normally the better economics.

Question 34

What is included in a containerised solution?

Accepted Answer

A containerised unit is a complete process line — machine, polymer preparation, pumps, control cabinet, piping and lighting — pre-assembled and tested in a sea container. On site you connect power, feed, filtrate return and cake discharge. That reduces installation to days instead of weeks.

Question 35

Which materials are used?

Accepted Answer

Standard construction is stainless steel 1.4301 (AISI 304) for the wetted parts. For chloride-bearing, saline or aggressive wastewater we use 1.4571 / 1.4404 (AISI 316Ti / 316L), and duplex or special alloys on request. DAF tanks are supplied in coated carbon steel as standard with stainless steel as an option. The material selection is confirmed against your water analysis before order.

Question 36

Do you provide material certificates and test documentation?

Accepted Answer

Yes. Material certificates to EN 10204 (2.2 or 3.1 depending on the component), welding documentation, pressure test records, factory acceptance test protocols and CE declarations are provided with the plant. Because the required scope differs from project to project, we issue this documentation with the order rather than publishing it here — tell us which certificates your specification requires and we confirm them in the quotation.

Question 37

Do you also provide engineering and commissioning?

Accepted Answer

Yes. We cover the complete scope: process design and mass balance, general arrangement and P&I drawings, manufacturing, factory acceptance test, delivery, supervision of installation, commissioning and operator training. For retrofits we also survey the existing structures.

Question 38

Are the technical data on this site binding?

Accepted Answer

No. The tables on our product pages are series data for pre-selection and give you realistic dimensions, weights, power and capacity ranges. Binding data — including exact dimensions, nozzle positions and guaranteed performance — is issued with the quotation and the general arrangement drawing for your specific project.

Question 39

Can you work to our specification and drawings?

Accepted Answer

Yes. We build to customer specifications including special materials, defined instrumentation brands, customer control philosophies and integration into an existing SCADA system. Tank and vessel engineering is also available as a standalone scope.

Question 40

Do you supply spare parts and service?

Accepted Answer

Yes. We supply original spare parts, filter cloths, screen baskets, wear rings and seals with short lead times, and we offer maintenance contracts and remote support. Because we also manufacture filter elements, wear parts are available directly rather than through a supply chain.

Question 41

How is the plant monitored and controlled?

Accepted Answer

Units are supplied with a PLC control cabinet and an HMI panel. Remote access for diagnostics and parameter adjustment is available, and signals can be integrated into your existing process control system via standard fieldbus or hardwired I/O.

Question 42

Which industries do you serve?

Accepted Answer

Food and beverage, dairy, slaughterhouse and rendering, chemical and pharmaceutical, metal processing and surface finishing, plastics, pulp and paper, recycling and energy, plus municipal wastewater treatment plants and their sludge lines.

Question 43

Where are you located and where do you deliver?

Accepted Answer

Our head office is in Hildesheim, Lower Saxony, Germany. We deliver and commission projects across Europe and handle export projects beyond it. All enquiries are handled in writing by email so that every technical request is documented and reaches the right process engineer directly.

Frequently asked questions

Technology selection

Cloth filtration

Sludge dewatering

Flotation and chemicals

Biological treatment

Rental and pilot testing

Engineering, materials and documentation

Service and spare parts

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