Nalco organic chemical program improves process efficiency, reduces costs by US $36,000 at Indian glass manufacturing plant |Â A major glass manufacturer in India needed to improve the wastewater treatment of its silica processing unit. The customer processed the raw sand acquired from mining, based on the quality requirement (size and colour) of production. Raw sand needed to be crushed, washed by water, and segregated, based on the particle size requirement, before being used as the raw material to manufacture glass of various kinds. This silica-processing unit had a wastewater treatment plant with a capacity of 400m3/hour.
The customer wanted to improve the sand-settling characteristics by reducing the silica particles in the water, so that water could be recycled for sand washing, which was ultimately aimed at getting the appropriate type and quality of sand for glass manufacture. After sand washing, the sand particles used to go through a primary clarifier, so the water could be recycled to the silica-sand washing unit for further processing. However, due to improper settling, fine sand particles used to flow into the primary clarifier.
The treatment by a local competitor of using alum, lime, etc., resulted in contamination of the sand. The turbidity of the outlet water was in the range of 25-60 NTU, as it failed to settle fine sand particles. Apart from high turbidity in the recycled water, huge manpower and energy costs were incurred to make the solution of the treatment chemical, in each shift. Further, the plant also had to incur a high cost on electricity to drive the stirrer to mix alum, lime and polymer.
Naturally, the customer sought an effective solution to improve the efficiency of the wastewater treatment process in his plant, through better sand-settling characteristics and optimised chemical consumption, so that the water could be recycled for sand washing without introducing any contaminants. In the meantime, the total cost of operation could be reduced by decreased energy and manpower costs.
In order to meet the client’s challenges, Nalco conducted several bench-scale trials. An all-organic coagulant and flocculant treatment program was introduced to replace the former inorganic products (alum, lime and polymer), with the suggested dosages. This was done to improve the treated effluent quality of the clarifier overflow water in terms of turbidity and total suspended solid (TSS) reduction.
Based on the bench scale trials, conducted onsite, Nalco recommended the following chemical products and dosages:
- Â Coagulant program: Nalco 8100 at 0.7 PPM
- Â Flocculant program: Nalco 7763 at 0.3 PPM
As an all-organic program, which is totally water soluble, the proposed treatment was not going to add any additional contaminants to the settled sludge, thus fulfilling the key requirements of the customer. Nalco’s treatment program which involved using coagulant (N 8100 @ 0.7 ppm) and flocculant (N 7763 @ 0.3 ppm) resulted in the following benefits to the customer:
- Â Effluent water quality improvement
After Nalco treatment, the water turbidity was significantly lowered from 25-60 NTU to 5-20 NTU, which was down by nearly 60%. The total dissolved solids of the recovered water was reduced by 70%. As the effluent water quality was improved, more water could be recycled for sand washing. Besides, the water consumption for batch preparation was reduced from 12 m3 to 6m3 per day, thereby saving the money spent, annually, by half.
- Electricity saving
The application of Nalco organic chemical products reduced the stirrer’s running time from 24 hours/day to only 1.5 hours/day, contributing to an annual saving of US $12,455.
- Â Chemical reduction
The inorganic products which were used, previously, were totally eliminated, bringing alum consumption from 43,800 kg/year to 0, lime consumption from 21,900 kg/year to 0, and polymer consumption from 16,425 kg/year to 0, thereby achieving a total annualised saving on chemical use of US $23,240.
- Â Manpower cost saving
The labour operation time taken to mix the alum and lime was reduced significantly, saving manpower costs by nearly 50%. The organic chemical program of Nalco, combined with its onsite expertise and application knowledge, delivered significant improvements that were required by the customer. The improvement in process efficiency, and the overall reduction in the total cost of operations, convinced the customer of the capability of Nalco to provide them with a sustainable solution, which was in keeping with their long standing expectations.
Sanjay Patil
Account Manager WPS, India
Nalco