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The pulp and paper (P&P) industry worldwide has achieved substantial progress in treating both process water and wastewater, thus limiting the discharge of pollutants to receiving waters. This review covers a variety of wastewater treatment methods, which provide P&P companies with costeffective ways to limit the release of biological or chemical oxygen demand, toxicity, solids, color, and other indicators of pollutant load. Conventional wastewater treatment systems, often comprising primary clarification followed by activated sludge processes, have been widely implemented in the P&P industry. Higher levels of pollutant removal can be achieved by supplementary treatments, which can include anaerobic biological stages, advanced oxidation processes, bioreactors, and membrane filtration technologies. Improvements in the performance of wastewater treatment operations often can be achieved by effective measurement technologies and by strategic addition of agents including coagulants, flocculants, filter aids, and optimized fungal or bacterial cultures. In addition, P&P mills can implement upstream process changes, including dissolved-air-flotation (DAF) systems, filtration save-alls, and kidney-like operations to purify process waters, thus reducing the load of pollutants and the volume of effluent being discharged to end-of-pipe wastewater treatment plants. Keywords: Wastewater treatment; Pulp and paper manufacturing; Advanced oxidation; Membrane technologies; Clarification; Activated sludgeContact information: a: North Carolina State University, Dept. of Forest Biomaterials, Campus Box 8005, Raleigh, NC 29695-8005; b: WestRock Company, Water and Waste Treatment, 600 S 8th St, Fernandina Beach, FL 32034; c: Department of Agricultural and Forestry Engineering, University of Valladolid, Campus Duques de Soria, E-42004 Soria, Spain; d: Complutense University of Madrid, Department of Chemical Engineering, Ingn. Quim, Facultad de Ciencias Químicas, Ciudad Universitaria s/n,S-N, E-28040 Madrid, Spain; e: Concordia University, Dept. Bldg. Civil & Environm. Engn., 1455 Maisonneuve Blvd, West Montreal, PQ H3G 1M8, Canada; f: University of Jyväskylä, Dept. Chem., Box 35, FI-40014 Jyväskylä, Finland; g: Department of Biology, Center for Environmental and Marine Studies, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal; h: Department of Environment and Planning, Center for Environmental and Marine Studies, CESAM, Aveiro & Department of Materials and Ceramics, Institute of Materials, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal; i: FPInnovations, 570 St. Jean Blvd., Pointe Claire, PQ H9R 3J9, Canada; * Corresponding author: hubbe@ncsu.edu Contents of the Article INTRODUCTIONThe pulp and paper (P&P) industry occupies a challenging position with respect to the natural environment. On the positive side, the industry is based on the usage of renewable, photosynthetic resources. On the other hand, the industry discharges huge quantities of aqueous effluents. Large volumes (up to 70 m 3 ) of wastewater ...

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BSTRACT: The conventional anaerobic digestion process, requiring long solids retention times (SRTs) to digest solids, is currently viewed as impractical for the pulp and paper industry because of high capital costs associated with the construction of new digesters. Recent developments in sludge solubilization technology could be promising in reducing digester size, which also allows for the potential use of decommissioned tanks, both of which can reduce the capital cost. Three pretreatment technologies for use with anaerobic digestion were tested on laboratoryscaie to investigate their feasibility. The SRTs in all three digesters systematically decreased from 20 to 3 days. The reference digester was fed waste activated sludge (WAS) to serve as the control at the same SRTs. The other digesters were fed WAS that had been preconditioned using mechanical shearing, sonication, or high-pressure homogenization technology. Anaerobic digestion with high-pressure homogenization produced as much methane at 3-day mean SRT as that from the reference digester operated at 20-day SRT. Therefore, a new digester can theoretically be 85% smaller than a conventional digester. An added benefit of WAS to methane conversion is the recovery of nutrients nitrogen and phosphorus. Water Environ. Res., 84, 497 (2012).

In municipal and industrial practices, wastewater treatment sludges are generally conditioned with organic polymers before dewatering. The dewatering polymers are expensive and contribute significantly to the overall sludge management cost. This paper discusses a preconditioning strategy that holds great promise for enhancing dewatering properties of wastewater treatment sludges, while reducing the cost. In this approach, the waste activated sludge (WAS) is briefly preconditioned with an acid before flocculating with an organic polymer. Experimental results showed that acid preconditioning significantly enhanced dewatering. Separately acidifying WAS and subsequently combining it with primary sludge produced higher presscake solids than acidifying the combined sludge to the same final pH. Acidification exhibited the added benefit of reducing Escherichia coli counts in sludge, thus improving its biological character. This may provide flexibility in choosing a beneficial use application. Water Environ. Res., 79, 168 (2007).