Developments in wastewater purification

Polymer-based spherical adsorbents (Saratech) for water and wastewater treatment.
Polymer-based spherical adsorbents (Saratech) for water and wastewater treatment.
The Saratech adsorbents show high purity, low ash content and negligible dust formation.
The Saratech adsorbents show high purity, low ash content and negligible dust formation.

One company has developed an adsorbent material that could provide numerous advantages over conventional AC.

The supply of clean water is not only essential, but also ambitious. Looking towards the future, simply treating water is not going to be enough. However, generating water in high quality while saving resources, health and the environment is a challenge.

The polymer-based spherical AC, seen in Figure 1, derives from a synthetic resource, ensuring a consistent and reproducible quality. Blücher‘s patented production process creates an adjustable pore system, high pore volumes and inner surfaces of up to 2,100 m²/g. The inner surface of only a few grams is equal to the surface of a football stadium of 10,000 m². Its chemical resistance, hydrophobic surface and bacterial-inhibiting effects offer further advantages in water and liquid treatment. These characteristics enable the application of Saratech adsorbents in various application fields. Undesirable substances can be removed from water as well as valuable substances can be recovered.

The most commonly used applications are the removal of micro pollutants (e.g. pharmaceuticals and pesticides), polar organic substances, volatile organic compounds (VOC) or total organic carbon (TOC) traces, chlorine and disinfection by-products as well as radionuclides like Cesium, Strontium and Iodine. Saratech adsorbents are also used in the recovery and enrichment of substances (e.g. caffeine) and in analytical determinations.

To gain an understanding of how Saratech adsorbents serve in water purification, the following sections present a closer look into selected projects.

Wastewater treatment from pharmaceutical productions

In the pharmaceutical industry a broad range of products and varying market demands require flexible production processes. For changing processes, frequent and thorough cleaning of vessels and equipment are necessary, generating high amounts of contaminated water and high disposal costs for the manufacturer.

Recently, Blücher realized a project in cooperation with a pharmaceutical manufacturer at a production site in Germany to reduce these disposal costs. The manufacturer uses a cleaning-in-place (CIP) operation to rinse the vessels and equipment after each batch or after process and product changes. The wastewater from the CIP operation is contaminated with tensides and pharmaceutical residues in varying amounts and with varying concentrations. Due to the manufacturer’s self-imposed obligations, the wastewater is not released into a municipal wastewater plant, as these contaminants can cause health and environmental hazards. In previous times, large streams of wastewater were thus incinerated, leading to an extensive energy demand and high disposal costs. In the collaborative project by the pharmaceutical manufacturer and Blücher, a sustainable solution to minimize the hazards and the costs involved was found.

In the first phase of the project, Blücher implemented a pilot plant on the production site and investigated the adsorption of tensides and pharmaceutical residues from the CIP wastewater. The pilot plant consisted of an ultrafiltration membrane followed by an adsorptive treatment step with Saratech adsorbents. Additionally to pharmaceutical residues, important sum parameters like TOC, CSB and AOX were monitored by sampling analysis. Two types of Saratech adsorbents were tested; one of them was selected due to higher performance.

The AOX curve shows a typical breakthrough process, exceeding the AOX limit value after 1.2 m³/kg (limit concentration: 1,000 mg/L). The CSB and TOC curves fluctuate, the CSB curve exceeds the limit value after approximately 0.7 m³/kg (limit concentration: 1,400 mg/L). For TOC, no specific limit value exists; however, the TOC is proportional to the CSB. The TOC curve is the first to show the breakthrough of all curves, and therefore, indicates the need to exchange the adsorbents. As the sampling analysis is a time- and cost-consuming procedure, an online TOC measuring system was installed to continuously monitor the concentration and hence, register a breakthrough.

The pilot plant successfully treated more than 300 m³ wastewater remaining contamination concentrations under limit values. Calculations on disposal costs revealed savings of up to 20%. These results paved the way for the scale-up of the wastewater treatment with the use of Saratech adsorbents.Since spring 2017, the second phase of the project has been running. A full-scale wastewater treatment plant on site is in operation and treats 1 m³ wastewater per day that is subsequently released into the municipal wastewater treatment. The adsorption results from the pilot plant trials could successfully be transferred to the full-scale application.  

Blücher accompanied the pharmaceutical manufacturer through the entire project, from start until today; including engineering, execution of pilot trials, full-scale installation and support and maintenance with adsorbent changes and continuous monitoring and evaluation of data. The reduction of the disposal costs using Blücher’s solution, creates a ‘win-win’ situation for both parties.  

UPW for the electronics semiconductor industry

Besides wastewater purification, the adsorbents are applied in the generation of ultra-pure water (UPW). Many products and processes require water in a quality that exceeds drinking water quality. By definition, UPW contains only H2O-molecules as well as H³O+ and OH- ions in equilibrium. In the electronics semiconductor industry, the increasing miniaturization obliges UPW for production processes. This challenges a water purification polishing method that does not only provide excellent adsorption performance but also ensures no abrasion or dissolution of material into the treated water. The Saratech adsorbents meet these criteria, combining the reliable removal of organic traces from water with the mechanical stability and the absence of water extractable substances.  

This second project was implemented together with a prime contractor and took place at a semiconductor production facility. Blücher was able to meet the strict requirements for UPW production by implementing its adsorbents in the process. The main challenge was decreasing TOC concentration from 250 ppb to extremely low concentration (< 10 ppb).

At the beginning of the project, Blücher selected adequate adsorbents and executed static batch experiments for the process design. The following diagram (Figure 3) presents the results of the experiments. The loading of TOC on the adsorbent material is plotted against increasing inlet concentrations for different material types. Except for Saratech type 4, all adsorbent materials show continuously increasing loadings for increasing inlet concentrations; therefore, type 4 was excluded from further investigations. While the competing product and Saratech type 1 show similar behavior, type 2 and 3 show significantly higher loadings and therefore, better performance for the removal of TOC from water.

Since 2017, a full-scale water treatment plant for the purification of UPW-recyclate using the adsorbents is running, meeting the quality requirements (< 10 ppb) and purifying UPW-recyclate for the production of semiconductors.