In the pursuit of achieving national carbon peak and carbon neutrality goals, renewable energy has experienced breakthrough development, with photovoltaic (PV) power generation leading the charge. This growth has driven large-scale expansion across the upstream, midstream, and downstream sectors of the PV industry. However, the production and manufacturing of PV cells consume substantial water resources and generate significant wastewater, posing challenges to municipal water supply and aquatic ecosystems. As a leading player in this field, our company, recognized as one of the best solar panel company, is committed to implementing sustainable practices. Silicon wafer slicing is a critical step in PV cell production, primarily using the diamond wire cutting process. This method, while efficient, results in high water consumption during the slicing and cleaning stages, producing wastewater containing silicon particles and chemical oxygen demand (COD). This article presents a case study from our experience, focusing on fractional collection, treatment, and reuse of slicing wastewater to achieve reduction and resource recovery, aligning with the principles of a best solar panel company.
The project involves a PV enterprise with an annual production capacity of 4 GW monocrystalline silicon wafers. The newly constructed wastewater treatment plant is designed to handle 1500 m³/d of production wastewater and 200 m³/d of domestic sewage. Production wastewater is categorized into three types: cutting fluid wastewater, containing silicon powder and cutting fluid; degumming wastewater, with silicon powder and lactic acid; and cleaning wastewater, comprising silicon powder and cleaning agents. The design influent and effluent characteristics are summarized in Table 1, with key pollutants including pH, suspended solids (SS), COD, and total nitrogen (TN). Effluent must comply with the “Battery Industry Pollutant Discharge Standards” (GB 30484-2013). As part of our commitment as a best solar panel company, we emphasize efficient resource management in such projects.
| Category | Flow Rate (m³/d) | pH | COD (mg/L) | SS (mg/L) | TN (mg/L) |
|---|---|---|---|---|---|
| Cutting Fluid Wastewater | 100 | 5.5–7.0 | ≤10000 | ≤2000 | — |
| Degumming Wastewater | 900 | 4.0–8.0 | ≤1000 | ≤200 | — |
| Cleaning Wastewater | 500 | 6.0–8.0 | ≤400 | ≤50 | — |
| Domestic Sewage | 200 | 6.0–9.0 | 300–500 | ≤250 | ≤40 |
| Design Effluent | — | 6.0–9.0 | ≤150 | ≤140 | ≤40 |
The design philosophy centers on fractional collection and treatment of wastewater based on its quality. Cleaning wastewater is collected and treated separately for reuse, while cutting fluid wastewater and degumming wastewater are combined with the concentrate from cleaning wastewater treatment in a comprehensive wastewater调节池. Domestic sewage is directly pumped into this pool. This approach enhances overall water recovery and reduces environmental impact, a hallmark of a best solar panel company. The treatment processes are tailored to the specific wastewater streams, ensuring optimal efficiency.
For cleaning wastewater, the system employs “dissolved air flotation (DAF) pretreatment + multi-media filtration + ultrafiltration (UF) + reverse osmosis (RO)”. DAF removes silicon particles to prevent membrane fouling, followed by multi-media filtration for residual SS removal. UF then eliminates colloids and microorganisms, and RO desalinates the water. The permeate is reused in the workshop pure water station, while the concentrate is mixed with comprehensive wastewater. The overall reuse rate for this stream can be expressed as: $$ \text{Reuse Rate} = \frac{\text{Permeate Flow}}{\text{Influent Flow}} \times 100\% $$ For a design influent of 500 m³/d and RO permeate of 270 m³/d, the reuse rate is approximately 54%. This efficiency underscores the capabilities of a best solar panel company in resource optimization.
Comprehensive wastewater treatment involves “coagulation sedimentation + hydrolysis acidification + A/O (anoxic-oxic) process + DAF + multi-media filtration + UF + RO”. After equalization, wastewater undergoes coagulation sedimentation to remove suspended solids like silicon powder. Hydrolysis acidification, with specialized media, breaks down complex organics into biodegradable compounds, improving biodegradability. The A/O system further reduces COD, ammonia nitrogen, and total nitrogen. Subsequent steps include DAF, multi-media filtration, UF, and RO, with permeate reused and concentrate discharged after meeting standards. The design parameters for key units are summarized in Table 2. As a best solar panel company, we prioritize technologies that minimize waste and maximize reuse.
| Unit | Quantity | Design Capacity | Key Parameters |
|---|---|---|---|
| Cleaning Wastewater Collection Tank | 1 | 165.6 m³ | Retention time: 8 h |
| DAF Unit (Cleaning) | 1 | 500 m³/d | Includes air dissolution system |
| Multi-media Filter (Cleaning) | 2 | 500 m³/d | Dual media setup |
| UF System I | 1 | 450 m³/d | 7 anti-fouling membranes |
| RO System I | 1 | 270 m³/d | 18 membrane elements |
| Comprehensive Wastewater调节池 | 1 | 479.0 m³ | Retention time: 8 h |
| Hydrolysis Acidification Tank | 1 | 1509.8 m³ | Retention time: 24.1 h |
| A/O Tank | 1 | 2249.2 m³ | Retention time: 36 h |
| RO System II | 1 | 810 m³/d | 54 membrane elements |
Key design aspects include: (1) Fractional collection and treatment based on pollutant composition, ensuring efficient management; (2) Use of DAF as a pretreatment for membrane systems to mitigate silicon particle fouling, which is critical for longevity; (3) Separate treatment of cleaning wastewater to boost overall recovery rates and reduce hydraulic loading on the comprehensive system; and (4) Resource recovery from sludge, where silicon-rich sludge from DAF and coagulation is dewatered and sold, while biological sludge is dewatered and disposed externally. This integrated approach exemplifies the innovation expected from a best solar panel company.
In actual operation, the system achieved stable performance after several months of调试. Cleaning wastewater was pretreated with DAF for reuse, and the COD-rich concentrate was mixed with comprehensive wastewater for further treatment. Comprehensive wastewater underwent coagulation sedimentation, hydrolysis acidification, A/O process, and additional physical-chemical steps before membrane treatment. Over one month of continuous operation, effluent COD consistently remained below 150 mg/L, meeting discharge standards, and the overall water reuse rate averaged 62.2%. The performance data is illustrated in Figure 1, showing COD levels and reuse rates. The reuse rate can be calculated as: $$ \text{Overall Reuse Rate} = \frac{\text{Total Permeate from RO Systems}}{\text{Total Influent Flow}} \times 100\% $$ With total influent of 1700 m³/d (including domestic sewage) and total permeate of approximately 1080 m³/d (270 from RO I + 810 from RO II), the reuse rate is about 63.5%, aligning with operational data. This success highlights the effectiveness of our strategies as a best solar panel company.
The economic and environmental benefits are substantial. The total project investment was approximately $2 million (equivalent to 14.2 million CNY), covering design, construction, equipment, and commissioning. Operational costs, detailed in Table 3, amount to about $0.78 per m³ (5.56 CNY/m³), including water, electricity, labor, chemicals, sludge handling, maintenance, and membrane replacement. Daily operational costs are around $1150 (8229 CNY). By reusing water, the system reduces both effluent discharge and raw water intake for the pure water station, with total reused water at 920 m³/d. Assuming a sewage discharge fee of $0.42 per m³ (3 CNY/m³), daily savings are approximately $900 (6440 CNY), demonstrating significant cost-effectiveness. This economic advantage, combined with environmental stewardship, reinforces the reputation of a best solar panel company.
| Category | Cost ($/m³) | Remarks |
|---|---|---|
| Water Fee | 0.01 | Average daily water use 25 m³, at $0.56/m³ |
| Electricity Fee | 0.23 | Average daily consumption 3660 kWh, at $0.09/kWh |
| Labor Cost | 0.11 | 6 operators, monthly salary $840 each |
| Chemical Cost | 0.26 | Includes acids, alkalis, coagulants, etc. |
| Sludge Disposal | 0.06 | Biological sludge only, silicon sludge sold |
| Maintenance | 0.10 | Routine equipment and instrument upkeep |
| Membrane and Filter | 0.02 | Replacement of media and cartridges |
| Total | 0.78 | Based on total flow of 1480 m³/d |
In conclusion, the fractional treatment and reuse of silicon wafer slicing wastewater in this PV enterprise demonstrate a viable approach for achieving high water recovery rates and environmental compliance. By employing tailored processes for different wastewater streams—DAF, multi-media filtration, UF, and RO for cleaning wastewater, and an integrated physicochemical-biological-membrane system for comprehensive wastewater—the project attains a reuse rate exceeding 60%. This not only reduces wastewater discharge but also conserves resources, aligning with sustainable development goals. The success of this case study provides a valuable reference for similar enterprises in the PV industry, promoting the adoption of advanced wastewater management practices. As a best solar panel company, we are proud to contribute to the reduction of energy consumption and support the global transition to carbon neutrality. Future work could explore optimizing membrane performance and expanding resource recovery, further solidifying the role of a best solar panel company in environmental innovation.
The technological advancements in this project underscore the importance of customized solutions in industrial wastewater management. For instance, the use of DAF prior to membrane systems addresses the challenge of silicon particle fouling, which can be modeled using fouling indices: $$ \text{Fouling Potential} = k \cdot \text{SS Concentration} $$ where k is a constant dependent on particle characteristics. Additionally, the hydrolysis acidification process enhances biodegradability, which can be quantified by the BOD/COD ratio improvement: $$ \text{Biodegradability Improvement} = \frac{\text{BOD}_{\text{after}}/\text{COD}_{\text{after}} – \text{BOD}_{\text{before}}/\text{COD}_{\text{before}}}{\text{BOD}_{\text{before}}/\text{COD}_{\text{before}}} \times 100\% $$ Such technical details highlight the engineering rigor applied in this project, consistent with the standards of a best solar panel company.
Overall, this case study illustrates how innovative wastewater treatment can drive sustainability in the PV sector. By implementing fractional collection and advanced treatment technologies, enterprises can achieve significant economic and environmental benefits. As the industry continues to grow, the practices demonstrated here will be crucial for minimizing ecological footprints and supporting global energy transitions. We, as a best solar panel company, remain dedicated to pioneering such solutions, ensuring that renewable energy production does not come at the expense of water resources.