The sludge transfer is a complex operation which can be managed by PEMO pumps. It involves several sectors such as mining and quarrying one, stone, marble and granite processing, ceramic and paper industry, treatment of the organic fraction of urban solid waste and water purification.
All Perissinotto’s PEMO's range is indicated for this transfer procedure. In fact, for each of these sectors, the company offers models which are customizable according to the customer’s needs and that are well suited to the suction and transfer of dense, abrasive, acidic or purification sludge.
Slurry is nothing more than a mixture of a fluid (usually water) and some pulverized solid material. It is a heavy material, which may also contain volatile, abrasive or corrosive substances.
According to the solids it contains, the sludge is:
- sedimented, which contains coarse particles that make the mixture unstable;
- not sedimented, that is made up of fine particles that do not cause particular wear.
Regardless of the type of slurries, the choice of a sludge transfer pump must take into account the required flow rate and power. Furthermore, the possible erosion caused by physical friction or chemical reaction must also be taken into consideration, in the event that the handled mixture contains particularly abrasive or acidic particles.
Which pumps to use?
All the basic models of PEMO range can be adapted in vertical, horizontal, submerged or multistage versions. This gives rise to more than three thousand different possible configurations, so to handle any activity and need for sludge transfer.
Shafts, crankcases and bearings are oversized to increase mechanical life. However, thanks to a quality industrial design, the overall dimensions remain compact.
The open type impellers can be rubberized or metal: in the latter case they are usually made of Hardalloy PEMO (750-800 HB), AISI or Hastelloy C.
According to the customer’s needs, they can also be made in other metals or alloys.
The bodies are built in two separable parts and are mainly cast iron elements. However, some models are already available in PEMO Hardalloy and stainless steel, hastelloy or other metals, upon request.
The AO / AB and AO / AB / DC series horizontal models with side suction are particularly suitable for the transfer of concentrated or thickened sludge. In fact, they are able to control the pressure on the sealing elements, by keeping it lower than that of the incoming fluid. This reduces the wear of the seals and extends their life, improving the reliability of the product.
High pressure pumps for filter presses are particularly suitable for sewage sludge transfer. PEMO offers over 40 models, in one, two or three-stage versions, with flow rates up to 1,100 m3 / hour and pressures up to 21 bar.
Sludge transfer: operations
The sludge transfer is a procedure that may differ depending on the industry in which it takes place.
The water purification sector is perhaps the one that gives us a more precise idea of the operations required during the transfer of sludge. Once the wastewater reaches a treatment plant, it has to go through several processes, some of which produce large quantities of sludge.
These sludge is distinguishable in:
Primary sludge are the deposits that form during the primary treatment. This happens after the wastewater passes into a clarifier or settling tank. It is held back until the larger and heavier solid particles settle to the bottom and the oil, fat and lighter solids remain on the surface.
Then the primary sludge is removed from the tanks with mechanical scrapers and pumps, so to be transported to the destination where they will be treated and/or reused.
Secondary sludge is generated by further treatment. In fact, the primary one removes only about 60% of the suspended solid particles.
Secondary treatment involves the removal of biological material and soluble materials that require oxygen for decay from the wastewater and the removal of any additional suspended solids. One of the most common methods of carrying out this treatment is the activated sludge process.
During this process, the wastewater and biological sludge are pumped into an aeration tank and mixed. Air is then injected into the mixture to help break down the biological material. Finally the mixture flows into a second clarifier or settling tank, where the activated sludge settles and it is pumped out.
Generally around 35% of the sludge is returned to the aeration tank, to help maintain a high population of microbes and break down the organic material. This sludge is commonly called active return sludge.
Since more activated sludge is produced than it is needed for the return sludge, any excess activated sludge is destined for disposal.
What kind of sludge can we transfer with the pumps?
Any Perissinotto’s PEMO pump facilitates the transfer of different kind of sludge, such as those:
- concentrated or thickened;
- abrasives or acidic.
The former are the main residue of the mechanical, chemical or biological purification treatments to which the wastewater is subjected before being returned to nature, so as not to damage the ecosystem.
This type of sludge is assimilated to waste, because the pollutants which are removed from the waste water are concentrated in it. In order to eliminate any possible sanitation problem, they must be treated before their use or disposal.
For handling this sludge, high pressure types for filter presses are particularly suitable. PEMO has developed over 40 models for this purpose and they are always customizable according to the customer’s needs.
The processes in the aggregates sector produce particularly dense sludge. Also in this case, PEMO's range of pumps is able to offer the optimal solution for moving them when they are concentrated in lagooning and feeding the hydrocyclones.
For the transfer of concentrated or thickened sludge, the horizontal PEMO's models AO / AB and AO / AB / DC series are used with lateral suction, which is able to control the maximum pressure acting on the sealing elements and reduce their wear, so to protect the durability and reliability of the pump.
The transfer of abrasive or acidic slurries subjects the pump to a particularly strenuous process. Since PEMO aims to limit wear and reduce the need for maintenance, our entire range maximizes the quality of impeller and body coatings.
Among PEMO products, the submersible ones are ideal for working with highly abrasive slurries. Equipped with a thermal probe for monitoring the engine temperature and an oil level probe, which is able to detect any infiltrations in the oil chamber, they also have a device capable of analyzing the signals coming from the probes.