## 2 Materials and Methods  
### Pilot System  
The pilot system replicates the core components of AC technology and was designed for a nominal flow rate of 0.5 L/s, with operational flexibility between 0.2 and 0.7 L/s. It includes the following unit processes:  
Figure 1: Comparison between the full-scale AC plant with a 10 L/s flow rate (**left**) and the PF200 (**right**) with a 0.5 L/s flow rate. A scale bar of 1 m scale provided for reference. 1. **Inlet and Coagulant Dosing:** Raw water mixed with coagulant is sourced from the rapid mix chamber of the benchmark facility, ensuring identical physical-chemical characteristics and water characteristics shared between the two systems. Flow is regulated by a PID loop using a 1.5\({}^{\prime\prime}\) motorized control valve and a SITRANS FM MAG 3100 flow meter from Siemens (Plano, TX, USA). The coagulant used is PCH-180 aluminum chloride hydroxide (PACI), with an active aluminum concentration of 5.6% by mass, sourced from the Holland Company (Adams, MA, USA). 2. **Flocculation:** Post-coagulation, water enters a flocculation unit comprising eight vertical 3\({}^{\prime\prime}\) PVC pipes with internal baffles to ensure uniform head loss. The segments are open at the top and include pipe stubs to accommodate the required height of the water column. 3. **Sedimentation**: Flocculated water flows into a clarifier made from 3\({}^{\prime}\) corrugated PVC pipe. This unit mimics the full-scale AC sludge blanket clarifier with \(\sim\)1 m sludge layer, a sludge compaction zone, and narrow-spaced settling plates. Water enters through a 3\({}^{\prime\prime}\) PVC manifold with nozzles for uniform distribution. Waste sludge is continuously drained from the sludge compaction zone via a 3/4\({}^{\prime\prime}\) motorized valve, with flow monitored by an SM6001 flow meter from IFM (Malvern, PA, USA). 4. **Filtration**: Clarified water is directed into a stacked rapid sand filter built from 14\({}^{\prime\prime}\) PVC pipe. The enclosed design enables backwashing via hydraulic siphon, while following the same inlet/outlet tank arrangement as in larger AC filters. The filter is 170 cm tall and includes four inlet and three outlet manifolds spaced 20 cm apart, creating six filtration layers with a total of 130 cm of anthracite media. Head loss is monitored using a liquid level sensor in the inlet tank, calibrated for 0-80 cm. Figure 2 shows a schematic drawing of the tested prototype. Raw water flow rate is measured by the flow gauge _q 1_ and adjusted by the control valve _CV 1_. It is then analyzed by the turbidimeter _NTU 1_, before passing through the rapid mix unit. Water is then fed into a baffled flocculator and subsequently into the bottom of the sludge blanket clarifier. Sludge drain rate is measured by the flow gauge _q 2_ and controlled by the control valve _CV 2_. Clarified water is collected by the manifold at the top of the clarifier tank, and the turbidity is measured by the _NTU 2_. Water is then fed into the filter inlet tank, where the water level is constantly monitored by the pressure gauge _p 1_. When the head loss reaches a tank capacity, the pressure gauge signals to open the control valve _CV 3_, which activates the backwash sequence. Filtered water is collected in the filter outlet manifold, and the turbidity is monitored by the _NTU 3_. A detailed manual, describing the materials, dimensions, and the fabrication process of the presented pilot unit prepared by the AC group, is provided in the Supplementary Materials S1. The pilot system incorporates a Supervisory Control and Data Acquisition (SCADA) setup for automated monitoring and process control. Unlike large-scale AC plants, which avoid electrical components to enhance resilience against power outages, in this study, automation enabled continuous experiments and real-time adjustment of system parameters without constant oversight of the system.