Tech ical Bu I let PDF Shell Chemical Company

1 Technical BuIletin f?&ra 93- 3b7J-67 - PDF. 88. Shell Chemical Company Activated Sludge Treatment of Ethoxylate Surfactants at High Industrial Use Concentrations by J. P. Salanitro, G. C. Langston, P. B. Dorn, and L. Kravetz Shell Development Company , Westhollow Research Center P. 0. Box 1380, Houston, Texas 77251-1380. Presented at the International Conference on Water & Wastewater Microbiology, Newport Beach, California, February 8-1 1, 1988, Vol. 1, Paper No. 21, Pages 1-6..". I '. Abstract and intact surfactant removal, nitrification, sludge The primary degradation of a linear alcohol ethox- floc characteristics and effluent toxicity (fish and ylate (AE) and a branched nonylphenol ethoxylate Daphnia) were followed during the adaptation (NPE) was investigated in bench-scale activated phases.

2 Sludge units treating a synthetic sewage feed. Bio- treaters were gradually adapted to 10-100 mg/J Experimental surfactant and effluents monitored for loss of non- Bench-scale biotreaters ionic ethoxylate, foaming, feed BOD removal, nitri- Three continuous bench biotreaters were seeded fication and biosolids growth. Both surfactants with mixed liquor suspended solids (MLSS) ob- were degraded at influent doses of 10-40 mg/L tained from a small domestic sewage treatment Substantial BOD breakthrough, loss of nitrification, plant in Harris County, Houston, Texas. These aerator foaming and incomplete removal of the units, described previously (Salanitro et a/.)

3 , 1983). NPE surfactant occurred when fed at 80 and 100 consisted of a three liter stirred, air-sparged aera- mg//while the unit treating AE was unaffected by tor and a one liter clarifier. Feed vessels and efflu- high surfactant levels. Comparative aquatic toxicity ent receivers were maintained at refrigerated tem- of the biotreated waste at high surfactant levels in- peratures. Units were operated at a feed rate of dicated that the NPE effluent was acutely toxic 88day, 15-20 day sludge residence time, aerator (EC50, 7-15% effluent) to the fathead minnow and MLSS of 2000-3000 mg/4 pH , dissolved oxy- Daphnia while that of the AE unit was non-toxic gen 2-4 mg//and a temperature of 23-25 C.

4 The (EC50, >lOOo/~ effluent) to these same species. OECD/EEC synthetic sewage (peptone, beef ex- These studies indicate that the treatment of wastes tract, urea and minerals) were similar to that de- containing high levels of NPE may adversely im- scribed by Painter and King (1978) except that pep- pact an activated sludge process in incomplete tone and beef extract were doubled. This feed degradation and foaming, impaired BOD removal, contained approximately 230-300 mg/L TOC, loss in nitrification and the formation of toxic efflu- 150-200 mg/! BOD, 400 mg/L COD, 65-80 mg//. ents. AE surfactants, however, undergo extensive Kjeldahl nitrogen (TKN), mg// NH3 and microbial degradation and cause little or no impact 20-30 mg/J PO4+.

5 Detergent addition to the bio- on the activated sludge treatment process. treaters was accomplished by pumping (Gilson Minipuls* 2 peristaltic metering pump) concentrat- Keywords ed filter-sterilized solutions through Won* and Ethoxylate surfactants; high use levels; activated Teflon* tubing at a constant flow (50 &/day). Fig- sludge treatment; BOD removal; effluent toxicity. ure 1 gives the general structures and molecular weights of the surfactants tested. The alcohol Introduction ethoxylate was commercial grade material and con- Studies on the biodegradation of nonionic tained a range of C,2-C,5 carbon atoms in the line- ethoxylate-type surfactants by activated sludge ar alkyl chain with an average polyoxyethylene microorganisms have demonstrated that linear al- chain length of 7 (NEODOLB 25-7, Shell Chemical cohol ethoxylates (AE) are rapidly and more com- Co.)

6 The NPE contained a highly branched alkyl pletely metabolized than nonylphenol ethoxylates chain made from propylene trimer and benzene (NPE) (Kravetz 1983 and Kravetz et a/., 1982). and an average polyoxyethylene chain length of 9. These findings were observed in shake flasks and (Igepal CO-630). Biotreaters were adapted to 0. bench biotreaters containing activated sludge inoc- (control) or 10-100 mg/J AE or NPE ethoxylate ula and treating synthetic or domestic sewage with over a six month period. surfactant levels of 5-20 mg/L Household nonionic Analysis of biotreatment parameters ethoxylates are typically present in untreated do- Influent and effluent samples from each activated mestic sewage at 5 mg/L However, little or no infor- sludge unit were taken once or twice per week and mation is available on the biotreatability of these analyzed for TOC total organic carbon), BOD (bio- compounds at potentially high industrial use con- Chemical oxygen demand, 5 days), ammonia centrations.

7 A comparative study was made, there- (NH4+), nitrate (NO3-), phosphate (P04-3) and fore, of the degradability of AE and NPE surfac- CTAS (cobaltothiocyanateactive substance for in- tants in bench-scale units adapted to 10-100 mg/J. ethoxylate. Operating parameters such as BOD. *Registered trademarks: Gilson Miniplus (Gilson Medical Elec- tronics, Inc.); Viton and Teflon (E. I. du Pont de Nemours &. Co., Inc.). 3. Figure 1/Test surfactants Average Molecular surfactant Structure Weight Nonylphenol CM3 CH3 CH3. Ethoxylate II II I 612. (NPE). Alcohol Ethoxylate (AE) 536. NEODOLs 25-7. tact ethoxylate surfactant ). TOC was determined CTAS were detected in the NPE effluent (up to on a Beckman Model 915 TOC analyzer and 40-55 mgM) during the 150 day period in which NH4+), PO4+, and NO3-) were estimated by NPE was fed continuously at 100 m g P (Figure 3).

8 Dionex* liquid chromatography. BOD, TKN and In contrast, the activated sludge unit treating the aerator MLSS were analyzed according to meth- AE readily adapted to all concentrations of influent ods outlined in Standard Methods (1985). The surfactant (10-100 mg//); effluent CTAS were sim- amount of intact surfactant in effluents (preserved ilar (<1 mgP) to the control. with 1% formalin) was analyzed by the CTAS A comparison of the ultimate biodegradability method (Boyer et a/., 1977). Intact surfactants and (transformation of organic carbon to C02) of AE. effluents from biotreaters degrading 100 mg// and NPE was made in a modified Sturm test ethoxylate were also subjected to aquatic toxicity (Sturm, 1973).

9 Acclimated activated sludge cul- testing using Daphnia pulex, fathead minnows tures from the AE and NPE units were incubated (Pimephales promelas), and Microtox* bacteria with 50 mglysurfactant and the rate of C 0 2 for- (Peltier and Weber, 1985 and Beckman, 1982, and mation measured over 14 days at 25 C. AE was Standard Methods, 1985). rapidly and extensively oxidized to 70-75% of the theoretical C 0 2 yield (Figure 4). Organic carbon Results and discussion from the NPE ethoxylate, however, was metabo- Biotreater effluent characteristics and surfactant lized to 2530% of the theoretical C 0 2 yield during degradation the same period.

10 Sodium benzoate, a positive con- During the detergent adaption period effluent BOD trol substrate, was also mineralized extensively remained <10 mg// in the control and AE units (80-90% of the theoretical yield) in seven days. (Figure 2) indicating that nearly all (>95%) of the These Sturm test data support the biotreatability biodegradable organics in the synthetic feed were observations that AE is biodegraded to C 0 2 more removed. Breakthrough of readily degradable feed completely than the NPE surfactant . constituents appeared in the effluent (BOD, 10-20 Foam height tests on biotreated effluents also mg//) of the NPE unit upon the step-increase to 80 confirmed that significant amounts of undegraded and 100 mgP surfactant .