Cost effective methodologies for the treatment of acid water in effluent treatment plant

Challenge Details

The effluent treatment plant (ETP) of a wire manufacturing industry handles 18,000 m³/month of effluent, collected from various units as represented in Figure 1. The constituents of the overall effluent are represented in Table 1. The overall process flow is represented in Figure 2.

Table 1: Constituents of the incoming effluent

The treatment process utilizes Lime for the neutralization of effluents. The current consumption rate of lime is 5.5kg/m³ of effluent. The use of lime results in 2 subsequent problems:

1. High Hardness (>2500 ppm) of the treated water - The desired hardness of treated water is 200 ppm. High hardness impacts the performance of the downstream reverse osmosis (RO) plant. For the reduction of hardness, Soda ash treatment is required, which increases the operational cost significantly.
2. Higher quantities of Red sludge generation (>200 MT/month) - Red sludge (Figure 3) consists mainly of iron, calcium, and magnesium. The sludge contains around 75% to 85% moisture, which increases the sludge disposal cost. The desired moisture content in Red sludge is < 30%.

We are seeking cost-effective treatment methodologies in the effluent treatment plant which can meet the following requirements:

• The alternative treatment methodology should be able to neutralize the acidic effluent.
• The hardness of treated water should be < 200 ppm.
• Moisture content in red sludge should be < 30%.
• The sludge generation should be reduced by 50%.
• The overall operational cost of the effluent treatment plant should be reduced.