Waste treatment and disposal aspects to development of California's pulp and paper resources ... : a cooperative study.

  • California. State Water Quality Control Board.
Date:
1957
Catalogue details

Licence: Public Domain Mark

Credit: Waste treatment and disposal aspects to development of California's pulp and paper resources ... : a cooperative study. Source: Wellcome Collection.

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    merely stored during periods of low flow and dis- charged when the rate of flow is high enough to render discharge harmless to the stream. Since the pH of this waste is essentially neutral, odor problems sometimes develop due to anaerobic decomposition during the storage period. This prob- lem may be overcome by concentrating the waste to 15% solids by evaporation prior to lagooning. The waste at this concentration manifests a bacteriostatic action, thus eliminating the odors. Land disposal by spray irrigation has been success- fully employed at a number of mills. The black liquor has been successfully used as a road binder for traffic- bound macadam surfaces. In some instances, the black liquor is concentrated and burned without accom- panying recovery of chemicals. Biological treatment employing a somewhat modified version of the basic high-rate activated sludge principle is also employed. BOD removals of 80% to 90% are obtained by this method. The most recent development in neutral sulfite semi- chemical waste abatement is the successful applica- tion of the recovery system, which has already been described. It is interesting to note that the recovery system provides pollution reductions comparable to those obtained by any of the above-mentioned treat- ments or effluent disposal schemes. In addition, it eliminates most of the color, which is not affected by biological treatment. It is realized that in some cases reductions of greater than 90% may be required. In such cases, treatment of the weak plant effluent after recovery of chemicals may be accomplished using the above-mentioned disposal plans or treatments. (b) Kraft—Kraft effluents are weak in comparison to those of other chemical pulping techniques since the recovery system which is always included in the process reduces the BOD, solids, and color to small fractions of the original concentrations. Where kraft mills are located on critical streams, oxidation ponds have often been successfully employed. These are large, shallow ponds (approximately 3 feet deep) which are seeded with bacteria, protozoa, and algae. The shallowness and large surface area accelerate the transfer of oxygen to the waste, which is necessary for aerobic metabolism. It is often found necessary to add nitrogen and phosphorus in proportions neces- sary to satisfy the inorganic nutritional requirements of the microflora in the pond. BOD removals of 75% to 98% have been obtained by this highly successful treatment. It can be truly stated that where land area is available and soil conditions do not endanger ground water supplies, this treatment method is by far the most economical and successful of all methods used to date. At sites where sufficient land area is not available, accelerated biological treatment has proven successful. Modifications of the activated sludge process have been installed yielding BOD reductions of 75% to 90%. 58 In a few instances, crop irrigation has been em- ployed as a disposal method. After a short storage period, the effluent is used to water such crops as corn, beans, alfalfa, ete. The results in increased crop yields have been extremely encouraging. The use of this method of disposal depends on the proximity of prod- uce farms. It has not yet been tested with a sufficient number of different types of crops, but its develop- ment shows promise. It has been noted previously that tastes and odors imparted to the receiving stream may be of concern, depending upon the mill location and the beneficial uses of the stream. Experimentation has shown that sulfides and mercaptans are the most probable source of tastes and odors, and that chlorination can effect satisfactory removal. (c) Sulfite—Sulfite waste liquor disposal has for many years been subject to intensive investigation directed toward the development of methods of treat- ment and by-products recovery. Much progress has been made, but to date there has been found no one solution applicable throughout the industry. Base chemical recovery, which has been discussed previously, would seem to be the ultimate solution, and the major effort of future research should be directed toward the solution of the remaining prob- lems in this process. Biological treatment of spent sulfite liquor has proved somewhat successful in small- scale semipilot plant research. BOD reductions of 70% to 85% have been obtained after 24 hours aera- tion. However, it has yet to be shown that these removals can be reproduced and sustained in a large- scale operation. The techniques of biological treatment used for domestic sewage are not directly applicable to industrial wastes—this is particularly true of spent sulfite liquor. Satisfaction of the air requirements and foaming problems encountered offer formidable hur- dles yet to be overcome. The tremendous size of the treatment plant required to treat this waste and the large amounts of biological solids produced, make it mandatory that a means be devised to market the by- products of treatment, which are essentially the bac- terial cells and the desugared lignin of the effluent. TABLE 28 DEBARKING EFFLUENT CHARACTERISTICS * Characteristic Quantity BODM5-day) s,s o- 58 soso ceee oe eee 5-20 lb/ton Total ‘solidss22ot teats err ee 0.1% of effluent (by weight) a. Total suspended solids__________ 30-50 lb/ton T=Mineral 2? 4. = eee 10% of suspended solids De Wissolved Bolids. 2 52-50 ae oes 50% of total solids de Mineral 224). 2 ee 50% of dissolved solids * Debarking effluent characteristics given represent effluents from aqueous debarking processes. As the water requirement decreases, the characteristics above will de- crease in magnitude. The figures above, therefore, are representative of the upper limits of debarking effluent characteristics.