Municipal Sludge Transfer — Replaced Submersible Pumps Across Multiple Sites

HERA Group — Municipal Wastewater Sludge Transfer

The Challenge

HERA (the Italian municipal utility group, operating across multiple cities) needed reliable sludge transfer at wastewater treatment plants. Municipal wastewater sludge presents a combination of challenges that eliminates most pump types: it contains solids and grit that plug centrifugal pumps, can foam heavily, requires self-priming from negative suction depths of 2–3 meters, and the pump must run dry without damage when the sump empties between cycles.

Submersible pumps were in use at some sites but suffered from clogging, inability to run dry, and difficulty inspecting and servicing equipment that is submerged in sewage.

The Solution

KECO specified Rotho M Series pumps (MS1, MS2, and MS2 D models depending on flow requirements) across multiple HERA sites. The peristaltic design self-primes reliably from -2 to -3 m suction depth without foot valves or priming systems. The pump can run completely dry without damage — an essential feature when intermittent sump level control means the pump may run empty at end of each cycle.

The HERA Forlì installation (2005) uses an MS2 on biological sludge at density 0.8, 3,000 L/h, -3 m suction. The tube had not required replacement at the time of the case documentation — an indicator of the low wear rate on low-density biological sludge.

"Hera Company choose our pumps because they are self priming and able to handle sludges with solid parts inside and foams with no contact with mechanical parts."

HERA Results

HOLCIM-BETON — Cement Washwater at 10–12 Bar

The Challenge

HOLCIM-BETON, the concrete division of HOLCIM (one of the world's largest cement companies), needed to filter the washwater from concrete mixer trucks at their France facility. The process involves pumping cement and sand slurry from the washwater pit up to an elevated filter press against 10–12 bar back-pressure, with -2 m suction and 8 h continuous daily operation.

The cement/sand mixture is highly abrasive and deposits rapidly. Without the filter press, the washwater requires treatment by specialized external cleaning contractors — a significant recurring cost.

Solution and Results

KECO specified a Rotho MS3 (M Series) with natural rubber tube, inverter-driven for variable flow control up to 15,000 L/h at 38 RPM. The MS3 generates enough pressure to pump against the 10–12 bar filter press back-pressure reliably.

Additional Water Treatment Installations

AGAC — Lime Slurry Dosing and Wastewater Sludge

AGAC (municipal utility, Reggio Emilia, Italy) operates multiple Rotho pumps. For lime slurry dosing — an abrasive and chemically aggressive product requiring negative suction — a Rotho PSF1 (S Series) handles 1,000 L/h at 2 bar with -2 m suction. Tube life: 4–5 months.

For wastewater sludge with gravels and solids, AGAC uses both the MS2 and the rare MS2 D (double-tube special variant) that enables pumping in two directions or two liquids simultaneously. Tube life: 6 months.

A.S.M. Mortara — 24-Hour Lime Slurry Dosing

A.S.M. Mortara (utility company, Pavia, Italy) runs Rotho MS1 and PSF1 pumps 24 h/day on lime slurry at density 1.2. The MS1 handles 1,000–4,000 L/h; the PSF1 handles 200–2,000 L/h. Both deliver very low maintenance on abrasive/aggressive product even at continuous heavy-duty cycle. Tube life: 6–7 months.

Early Adoption — HERA Cesena (1993)

One of the earliest documented Rotho installations is the HERA (then AMGA) wastewater facility in Cesena, Italy — dating to 1993. The MS2 has been pumping waste water and sludge over a 200 m pipeline (80 mm diameter) with -2 m suction since that installation, with 6-month tube replacement intervals. Over three decades of documented service in the same application is the strongest proof of long-term reliability available.