HBI-94-011-01
Pub. 10/31/94
The amount of pollutants and waste generated by industrial facilities has become an increasingly costly problem for manufacturers and a significant stress on the environment. Companies, therefore, are looking for ways to reduce pollution at the source as a way of avoiding costly treatment and reducing environmental liability and compliance costs.
The United States Agency for International Development (USAID) is sponsoring the Environmental Pollution Prevention Project (EP3) to establish sustainable programs in developing countries, transfer urban and industrial pollution prevention expertise and information pollution prevention expertise and information, and support efforts to improve environmental quality. These objectives are achieved through technical assistance to industry and urban institutions, development and delivery of training and outreach programs, and operation of an information clearinghouse.
EP3 pollution prevention diagnostic assessments consist of three phases: pre-assessment, assessment, and post-assessment. During pre-assessment, EP3 in-country representatives determine a facility's suitability for a pollution prevention assessment, sign memoranda of agreement with each facility selected, and collect preliminary data. During assessment, a team comprised of U.S. and in-country experts in both pollution prevention and the facility's industrial processes gathers more detailed information on the sources of pollution, and identifies and analyzes opportunities for reducing this pollution. Finally, the team prepares a report for the facility's management detailing its findings and recommendations (including cost savings, implementation costs, and payback times). During post-assessment, the EP3 in-country representative works with the facility to implement the actions recommended in the report.
This assessment evaluated a textile dyeing facility. The objective of the assessment was to propose a program of pollution prevention that would:
The assessment was performed by an EP3 team comprised of an expert in textile dyeing and a pollution prevention specialist.
This facility is an integrated textile mill. Starting with polyester and rayon viscose fibers, the facility produces dyed yarn and fabric and an average content of 65 percent polyester and 35 percent rayon. The facility employs 270 workers who work 296 days per year. In 1993, production volume was 1,134,059 kg of material dyed, with an additional 1,227,974 kg of fabric finished but not dyed.
Textile dyeing at this facility involves a number of steps that must be carried out in proper sequence and under optimal conditions. In general, the process involves filling tanks containing fabrics with water, and sequentially:
EP3 is sponsored by the U.S. Agency for International Development.
At the time of the assessment, there were a number of pollution problems at the facility, including:
The assessment identified eight pollution prevention opportunities that could address the problems identified above, with significant environmental and economic benefits to the facility. Table 1 lists the opportunities recommended for the facility, and presents the environmental benefits and implementation costs for each.
| Unit Operation | Pollution Prevention Action and Environmental/Product Quality Benefit | Cost | Financial Benefit | Payback Period |
|---|---|---|---|---|
| Recycling of dye cooling water | Install piping and valves - conserves water. | $750 | $400 per year | 20 months |
| Recycling of air conditioning system water | Install piping and a tank - conserves water and chemicals. | $6,700 | $4,900 per year | 14 months |
| Softener system | Install a digital hardness monitor - conserves water and chemicals. | $3,500 | $1,700 per year | 24 months |
| Solids in effluent | Install screens in drain line - reduces pollutant level in wastewater. | $600 | To be determined | To be determined |
| Operator work system | Deliver training - reduces power and water consumption. | To be determined | To be determined | To be determined |
| Steam traps | Implement maintenance plan - reduces VOCs. | To be determined | To be determined | To be determined |
| Bleaching | Recycle rinse water - reduces use of water and chemicals. | $2,200 | To be determined | To be determined |
| Boilers | Install a digital monitoring system - reduces emissions. | $1,000 | To be determined | To be determined |
| Power Consumption | Install a peak load generator. | To be determined | To be determined | To be determined |
| TOTALS: | $14,750 | $7,000 opportunity. | ||
Of the opportunities identified, three were studied in enough detail to quantify potential savings. For an investment of just under $11,000, the facility can reduce its water and salt consumption and save about $7,000 per year. The average payback period for these actions is approximately 20 months. Additional savings from bleach rinse recycling, steam trap repair, and boiler consumption efficiency changes were not quantified.
Well water with a hardness of approximately 600 ppm is pumped to a tank with a capacity of 60 cubic meters. From there, it is sent through a softener that reduces hardness to 3-5 ppm. This softened water is used for most factory processes. The cone-dyeing operation uses soft water for non-contact cooling in two places. The dye bath is cooled by passing soft water through the jacket of the dye tank. Non-contact cooling water is also used to cool the dye bath recirculating pump packing gland. Recycling these two streams is an opportunity and could be accomplished by sending the water back to the soft water pool that at the present time receives the cooling water from the jet dryers.
The air conditioner systems for the spinning and weaving rooms use soft water evaporation for cooling. The water currently used is taken from the softeners that serve the dye room. Fifty percent of this water is lost to evaporation, while the rest is dumped into the sewer system. This water use has caused problems in the dye room by causing shortages of soft water. The plant has purchased, but not installed, new softeners solely to produce water for the air conditioner system. When the new softeners are installed, the nonevaporated air conditioning system water should be recycled back to the new softener system.
The current dye room softener system has three softeners, each of which treat well water. In the wash, regeneration, and rinse steps, the operators calculate the water hardness using a colorimetric method. The wash time is excessive and the point at which the softeners are regenerated is chosen solely on the basis of time since the last regeneration, resulting in the loss of soft water. A digital system should be installed to determine the rinsing and service hardness end points, allowing operators to determine the exact end point for the wash period and the maximal supply capacity of each softener.
Five screens should be installed in dye room drains with the objective of reducing suspended solids in the effluent. The screens should be designed and installed to allow easy periodic cleaning. It is possible that in the near future the plant will need to install an industrial waste water treatment system; any decrease in loading now will allow a reduction in waste water treatment plant initial investment and running cost.
Operators of the dye machines have different methods for operating each machine, even though a procedure sheet is supposedly followed. At each shift change, the new operator switched to a different method, e.g., increasing the number of rinsing steps or changing the timing for the different processes. Because of this lack of process standardization, there are energy, water, and chemical losses. Training courses in standard operating procedures should be conducted.
Heat transfer losses caused by leaking steam traps amounts to about 10-15 percent of energy costs. Using leaking steam traps not only wastes energy, but also results in inefficient dye bath heating and the cost of damage to steam lines, valves, fittings, and other equipment. A training course for workers in the operation of ultrasonic equipment should be established and a preventive plan for maintenance of steam traps should be developed.
There is an opportunity to recycle rinse waters from the bleaching process by installing a 25 cubic meter tank to store the rinse water of one batch and use it for the one that follows. Thirty-six tons of product would need to be bleached to recover the initial $2,200 investment.
The combustion efficiency of the oil-fired boiler is not monitored continuously, but measured by an outside contractor four timer a year. Installation of a digital monitoring system will allow the efficiency of the combustion to be determined whenever parameters change, such as when a new lot of oil is received. This change will result in reductions in fuel use and particulate matter emissions. Payback time will depend on the amount of combustible efficiency improvement.
During 1993, the factory paid a total of $105,600 in maximum and peak demand power charges. Installation of a peaking generator could yield substantial reductions in net power costs, although net emissions effects will be negligible. If a natural gas generator is chosen and bio-gas from the local landfill is used, there may be a small net positive effect on emissions. While the size, and therefore cost, of the needed generator cannot be calculated, other textile plants have indicated a payback time of approximately 1 months.
For further information on this assessment or other activities sponsored by EP3, call the EP3 Clearinghouse at (703) 351-4004, send a fax to (703) 351-6166, or on Internet apenderg@habaco.com.