Sand Washing Plant Sludge and Sewage Treatment Case with Polyacrylamide

I. Project Overview

Client: XX Building Materials Sand Washing Plant (Medium Scale)

Project Location: XX Building Materials Industrial Park

Treatment Scale: The daily treatment capacity of sand washing sludge and sewage is 800-1000 m³. The sludge solid content is 15%-20%, and the main pollutants include quartz sand dust, sediment particles and suspended solids (SS). The wastewater is highly turbid, which fails to meet the local environmental protection standards if directly discharged. In addition, the accumulated sludge occupies the site, causing resource waste and environmental hazards.

Client Requirements: To realize the recycling of sand washing sewage, reduce the sludge volume through dehydration, and at the same time reduce the treatment cost and improve the sand washing production efficiency.

II. Project Pain Points

• The wastewater is extremely turbid with SS content reaching 3000-5000 mg/L, which is difficult to settle naturally after standing. Direct discharge will pollute the surrounding soil and rivers, leading to the risk of environmental penalties;
• A large amount of sludge accumulates, occupying the production site, resulting in high manual cleaning costs. Moreover, the sediment cannot be recycled, causing resource waste;
• The original treatment method (only adding lime) has poor flocculation effect, making sludge dehydration difficult. The sewage cannot be recycled, resulting in high water resource consumption;
• The treatment process is required to be simple and easy to operate, suitable for the continuous production rhythm of the sand washing plant without affecting the normal production capacity.

III. Solution (PAM Selection + Treatment Process)

1. PAM Model Selection

Combined with the characteristics of sand washing sludge and sewage (mainly inorganic sediment particles, neutral to alkaline wastewater), after multiple lab tests and pilot tests, Anionic Polyacrylamide (APAM) was selected with a molecular weight of 12-18 million and a degree of ionization of 20%-30%. This type of PAM has excellent flocculation effect on inorganic suspended solids, fast sedimentation speed, and can quickly form large flocs. It also has the advantages of low dosage and low cost, which is suitable for the continuous treatment of sand washing sewage.

2. Overall Treatment Process

A closed-loop process of “Pretreatment → Flocculation Sedimentation → Sludge Dehydration → Clear Water Recycling” is adopted, which is simple in process, high in automation and does not require a lot of manual operation. The specific process is as follows:

1. Pretreatment: Sand washing sewage is collected in a sump, and large-particle impurities (such as stones and debris) are intercepted by a grid to prevent clogging of subsequent equipment;
2. Flocculation Sedimentation: The pretreated sewage is pumped into a reaction tank, and anionic PAM is added in proportion (dosage: 30-50 mg/L), together with Poly Aluminum Chloride (PAC) for auxiliary flocculation. Through full mixing by a stirring device, the sediment particles in the sewage quickly agglomerate to form large flocs, which settle rapidly after entering the sedimentation tank, and the supernatant enters the clear water tank;
3. Sludge Dehydration: The concentrated sludge at the bottom of the sedimentation tank (solid content increased to 30%-40%) is pumped into a plate and frame filter press, and a small amount of cationic PAM is added to assist dehydration. After pressure filtration, dry sludge cakes are formed (solid content ≥ 60%);
4. Clear Water Recycling: After testing, the supernatant of the sedimentation tank meets the standard and is directly reused for sand washing production to realize the recycling of water resources. A small amount of remaining qualified clear water can be directly discharged.

IV. Treatment Effect

After the project was put into operation, the specific data are as follows:

• Sewage Treatment Effect: The SS removal rate is ≥ 98%, the SS of the treated effluent is ≤ 50 mg/L, the turbidity is ≤ 10 NTU, and the pH value is 7.0-8.5, which meets the first-class discharge standard;
• Sludge Treatment Effect: After dehydration, the sludge forms dry cakes, the volume is reduced by more than 70%, and the dry sludge cakes can be recycled for brick making and roadbed filling, realizing the resource utilization of solid waste;
• Water Resource Utilization: The recovery rate of treated clear water is ≥ 85%, saving more than 700 m³ of fresh water per day, which greatly reduces the cost of water resources;
• Environmental Compliance: It completely solves the problem of random discharge of sand washing sewage, avoids environmental penalties, improves the environment of the plant and its surrounding areas, and has been recognized by the local environmental protection department.

V. Client Benefits

1. Cost Savings: It saves the cost of fresh water, sludge cleaning and the risk of environmental fines every day;
2. Efficiency Improvement: The treatment process operates automatically without special personnel on duty, which does not affect the sand washing production rhythm and increases the production capacity by about 10%;
3. Resource Recycling: The dry sludge cakes are recycled, realizing the dual environmental protection of “sewage recycling + solid waste recycling” and improving the green image of the enterprise;
4. Compliant Operation: It completely solves the environmental pain points, meets the local environmental protection policies, and provides a guarantee for the long-term stable production of the enterprise.

VI. Project Summary

For this sand washing plant sludge and sewage treatment project, by accurately selecting anionic PAM and matching with a scientific and reasonable closed-loop treatment process, it not only solves the core pain points of sand washing sewage pollution and sludge accumulation, but also realizes the recycling of water resources and the resource utilization of solid waste, taking into account environmental protection and economy. This case fully reflects the core advantages of PAM in sewage treatment in the sand washing industry – good flocculation effect, low dosage, low cost and easy operation. It is suitable for the sewage treatment needs of sand washing plants of various scales .