of the available screen in the factory proved to be very efficient in removing most of the particulates and organic matters,as indicated by the percentage removal of TSS (72%), COD (75%) and BOD (65.6%). The screened effluent was subjected then to a plain sedimentation for two hours. Although the results indicated a great improvement in the quality of the primary treated effluent, the residual values of TSS, COD and BOD still did not comply with the National regulatory standards for wastewater discharge into the public sewage network.
Screening followed by chemical coagulation/sedimentation process using the pre-determined optimum doses of alum(130 -150 mg/l), adied with 5 mg/l cationic polymer and at the optimum pH of -6.2+_0.2 resulted a good quality of the treated effluent. However, in some cases, some particulates were floated during the sedimentation process. Accordingly, dissolved air flotation using alum and the cationic polymer has been recommended [8]. Fig. 2 shows the schematic diagram of the proposed treatment train.
3.3 Second approach: implementation of pollution prevention measures
Industrial auditing at the factory revealed that all the processes are operated in an open circuit. To apply the scenario of pollution minimization and waste reduction, most of the open circuit processes have been changed to closed circuit type operation.
The technologies applied for pollution control in the mill were:
- Recovery of fiber.
- Reuse of clarified/unclarified white water at appropriate areas.
- Minimization of fresh water consumtion without affecting runability or quality.
The proposed solutions were already implemented at the factory. The economic return was calculated. Evaluation of the quality of the end-of-pipe ws. pollution prevention was also determined.