Introduction

As a crucial supporting industry for manufacturing, the electroplating sector has always faced challenges in environmental management due to the presence of heavy metals like chromium and nickel in its wastewater. Previously, we shared other successful electroplating wastewater ceramic membrane retrofit projects. Recently, a deep filtration system for electroplating wastewater in an industrial park in Chongqing was implemented. Anticipating the increased pollution concentration in the influent after the park's expansion, Jianmo also selected silicon carbide tubular ceramic membranes as the final-line treatment. This article details the implementation logic and application value of this process, based on the actual project conditions.

Project Basic Information

Wastewater Type: Chromium-containing rinsing wastewater, Nickel-containing rinsing wastewater

Applied Products: Integrated silicon carbide tubular ceramic membrane filtration system

Application Type: End-of-pipe deep filtration unit for wastewater, removing suspended heavy metals

Treatment Requirements: Stable production water meeting Chongqing local electroplating standards; proactive adaptation to future enterprise expansion and influent pollutant rise conditions; establishing a stable heavy metal compliance barrier in the workshop

Core Pain Points Solved: The clear water tank contains residual colloidal trace heavy metals; the heavy metal load in the influent will increase significantly due to future expansion of the enterprise; conventional filter media are not resistant to the acidic and alkaline water quality of electroplating and have a short service life.

Project Background

I. Strict Environmental Control Constraints

1. Article 45 of the *Water Pollution Prevention and Control Law of the People's Republic of China* (2017 Amendment): Toxic and hazardous industrial wastewater must be treated according to its classification and quality, and dilution and discharge are strictly prohibited;

2. The *Electroplating Pollutant Discharge Standard* (GB21900-2008) clearly defines chromium and nickel as Class I heavy metals, with monitoring points located at the workshop effluent outlets. Water bodies that do not meet the standards cannot be discharged into the general wastewater system;

3. Chongqing implements the *Chongqing Municipal Voluntary Discharge Standard for Wastewater Pollutants in the Electroplating Industry* (T/CQSES02-2017), with local standards exceeding national standards.

II. Urgent Need for Industrial Park Treatment

The industrial park has already established a complete pretreatment system for chromium and nickel-containing wastewater. Wastewater undergoes integrated treatment including reduction, neutralization, coagulation, sedimentation, and flotation before being discharged into the chromium and nickel clear water tanks. According to long-term water quality monitoring data from the clear water tank, trace amounts of colloidal heavy metals remain in the water, posing a potential risk of fluctuations in these levels.

In accordance with the regional industrial park's management requirements, the continued expansion of surface processing enterprises will significantly increase the concentration of heavy metal pollutants in their wastewater in the long term. Therefore, this project adds an independent deep filtration unit downstream of the existing clear water tank, using the increased water quality under enhanced load as the design boundary to proactively establish a stable heavy metal control line and ensure the stable operation of the downstream integrated biological treatment system.

Process Flow Description

This project is divided into two sections: the existing pretreatment system and the newly built silicon carbide ceramic membrane deep treatment system. Chromium/nickel-containing wastewater undergoes homogenization and equalization in the equalization tank and emergency tank, sequentially completing acid reduction, alkali neutralization, coagulation and flocculation, sedimentation, and flotation treatment. The effluent from the integrated equipment flows into the chromium/nickel clear water tank, serving as the influent source for the new membrane system.

The newly constructed silicon carbide ceramic membrane deep treatment system uses silicon carbide ceramic membrane filtration equipment as its core. After effluent from the chromium/nickel clear water tank, it first undergoes the addition of acids, alkalis, heavy metal scavengers, and PAC/PFS coagulants to further dissociate colloidal heavy metals from the water. Following coagulation and sedimentation, the water is then pumped into a silicon carbide tubular ceramic ultrafiltration unit. The silicon carbide ceramic membrane uses nano-sieving to trap colloids and fine heavy metal flocs in the water. The treated water enters an online heavy metal monitoring point. Water that passes the monitoring is directly sent to the park's integrated wastewater treatment system; unqualified water is automatically diverted to a resin ion exchange unit for further treatment until it meets standards. The membrane system performs automatic backwashing and periodic acid-alkali chemical regeneration at regular intervals. Backwash concentrate and circulating concentrate are all returned to the front-end coagulation sedimentation tank for closed-loop volume reduction treatment.

The selection logic and technical advantages of the silicon carbide ceramic membrane

This project adds a quality improvement unit to the end of the existing water treatment facility. The design needs to consider both the current trace heavy metal trapping in the clear water tank and the high-load influent conditions of future expansion. While organic ultrafiltration and sand filtration technologies can adapt to the current low-concentration water quality in the short term, their corrosion resistance and long-term retention stability cannot meet the demands of rising water quality in the long term. The project team, considering factors such as alternating acid and alkalinity in electroplating water, regulatory requirements, and the overall cost of equipment maintenance, determined that silicon carbide ceramic membranes offer the best long-term adaptability and comprehensive economic benefits, making them the core deep filtration technology for this project.

The core advantages of the silicon carbide ceramic membrane:

1. Adaptable to high long-term loads, with stable and controllable effluent indicators: Nanoscale sieving provides excellent retention of fine heavy metal flocs. Even with increased industrial activity, higher influent pollutant levels, or fluctuations in front-end sedimentation conditions, the turbidity and heavy metal levels in the effluent remain stable, mitigating the environmental risks associated with online exceedances.

2. Resistant to repeated acid and alkali cleaning, ensuring high equipment durability. The pure inorganic silicon carbide substrate has a wide pH adaptability range, allowing for long-term online regeneration under strong acids, alkalis, and oxidants. It avoids the problems of organic membrane swelling, fiber breakage, and short-term failure, perfectly adapting to the variable acidity and alkalinity of electroplating water.

3. Integrated skid-mounted structure for simple and efficient on-site installation. The membrane module, pump set, chemical tank, and electrical control system are integrated with a standardized operating platform. On-site installation only requires connection to water and electricity, and inlet/outlet water pipelines, significantly shortening the installation and commissioning cycle.

4. Extended service life, reducing long-term maintenance costs. The membrane element is designed for a long service life and excellent fouling resistance, significantly reducing the frequency of cleaning agent and filter media replacements. Equipped with a variable frequency energy-saving circulating pump, it reduces continuous operating costs over many years from multiple dimensions, including consumables, energy consumption, and labor, resulting in outstanding long-term economic efficiency.

On-site photos