|Ph.D Student||Lerner Mark|
|Subject||Wastewater Reuse for the Minimization of Fresh Water|
Consumption in Paper Production
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Emeritus Noah Galil (Deceased)|
|Full Thesis text|
In this research an innovative and advanced closure strategy approach for minimizing fresh water consumption for paper mills (PM) with multiple papermaking lines was developed. The proposed approach examines phenomenon of PM water loop closure strategy and offers effective and competitive solution for reduction of fresh water consumption taking into consideration process configuration and runnability, economic, and environmental aspects.
In the study Water Pinch Analysis was used in order to determine the achievable paper mill potential for water reuse. The possibility of reusing paper mill water streams from white paper into brown paper productions, and vice versa, was investigated by means of the "Water Design" computer program on the base of comparison of water quality parameters as COD, TDS, Ca Hardness and Color. It was found that Brown PM wastewater was not appropriate for reuse in White PM because of high concentrations of COD, TDS, Ca, and liquid color. In addition, the results of the computer program running showed that reuse of White PM wastewater into Brown PM without proper organic matter (COD) removal would be very problematic. Thus, treatment/regeneration of both brown and white PM wastewaters before their reuse was required.
The research examined such wastewater treatment alternatives as anaerobic-aerobic treatment with sand filter post-treatment, membrane bioreactor (MBR), activated carbon filter, softening and reverse osmosis on the base of many years' statistical measurements, full scale wastewater treatment systems experience, comparisons and cross-evaluations between the effluent and process quality, technical, economic, and environmental aspects.
The use of Water Pinch analysis and investigation of different wastewater treatment options show that optimal closure scheme for paper mill with brown and white paper producing lines should contain combination of anaerobic-aerobic treatment with softening, sand filtration and RO unit. The method proposes maximum fresh water reduction by 67.5% (i.e. new fresh water consumption is 2.6 m3/ton paper). In order to obtain such reduction of fresh water use, 25% of effluent must be reused into brown PM after softening and SF. The rest 56.5% of effluent must be treated by RO system for adjustment of the effluent quality for white and brown PM high requirements. After RO unit 20% of liquid can be used in brown PM and 22.5% in white PM.
Maximization of effluent reuse after softening stage, decreasing the quantity of liquid for RO treatment and lowering of RO brine formation allow achieving high economic savings with minimal negative environmental influences.