Don't Send Money Down the Drain

A versatile system meets Federal standards while minimizing VOCs in wastewater

By Terrence T. Virnig, P.E., C.H.M.M., Synthetech Inc., and John A. Meidl

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Newly mandated pharmaceutical pretreatment standards imposed by U.S. EPA and adopted by the city of Albany, Ore., have led Synthetech Inc. to install a wastewater treatment system. The new system not only enables the company to meet Federal and local pharmaceutical pretreatment standards, but also has saved it more than $18,000 per month in off-site disposal costs, sewer charges and local "site development charges."

 

Synthetech produces peptide building blocks and specialty amino acids that are distributed globally to major pharmaceutical companies. Synthetech offers more than 300 novel amino acids, alcohols, esters and amides for clinical development and commercial use. To help synthesize the products, chemicals are batch-manufactured in different quantities. This generates highly variable amounts of waste (Table 1), which are often challenging to treat safely and reliably.

Synthetech discharges its treated wastewater to Albany's publicly owned treatment works (POTW). The city has incorporated Federal Pharmaceutical Pretreatment Standards, which include the regulation of 23 volatile organic compounds (VOCs), pH and ammonia nitrogen into local codes. In addition to a limit on the amount of contaminants discharged, the city levies a site development charge (SDC) on manufacturers who send increased biochemical oxygen demand (BOD) and total suspended solids (TSS) loading to the POTW. The BOD loading for Synthetech was determined to be 195 lb/day, an amount that would significantly increase the manufacturer's SDC.

 

 

 

 

Initial development and testing
After the company implemented waste minimization measures and found them to be inadequate, Synthetech began an evaluation of several wastewater treatment methods, including UV/oxidation, granular activated carbon (GAC), evaporation and biological treatment alternatives. The company selected USFilter Zimpro Systems' Powdered Activated Carbon Treatment (PACT) system because of its ability to handle the highly variable types and concentrations of contaminants in wastewater streams.

To assess the performance of the proposed system and to gain insight into the challenges of treating the wastewater stream, USFilter and Synthetech bench-scale tested the system on an equal mixture of process and non-process (dilute) wastewaters. Testing results indicated that the PACT system could treat the VOCs, remove BOD and chemical oxygen demand (COD) and assimilate nitrogen (in biomass production) when treating the combined wastewater streams (Table 2). However, the effluent stream did not meet the 29 mg/L ammonia nitrogen limit due to the presence of components in the wastewater that would not allow biological nitrification to occur in the PACT system.

Since the ammonia could not be biologically nitrified to meet the required pretreatment standard, Synthetech and USFilter evaluated a number of treatment alternatives. These alternatives included the use of breakpoint chlorination of the PACT effluent to remove ammonia; the elimination of inhibitory components from wastewater within the production process; and the use of membranes and/or evaporation to remove total dissolved solids (TDS) from the wastewater. USFilter and Synthetech decided to use a small skid-mounted, factory-built evaporation unit that could eliminate TDS and control ammonia without fouling the evaporator (Table 3).

 

Figure 1. The system makes use of new and existing equipment to successfully treat the combined wastewater streams.

 The implementation
A full-scale system was designed and configured to treat Synthetech's combined wastewater streams. Installed in September 2001, it includes an evaporator to treat the process stream and a PACT system to treat the evaporator distillate and the non-process wastewater.

The process wastewaters are sent to the evaporator where high levels of TDS and problematic nitrogen compounds are eliminated (Figure 1). This makes removal of the remaining contaminants in the downstream PACT system more efficient. Initially, the pH of the concentrated waste was kept low to retain the ammonia in the evaporator concentrate, but this resulted in corrosion of the evaporator. Consequently, the pH of the feed was raised. In spite of increased ammonia levels in the feed to the PACT system, effluent concentrations remain at acceptable levels.

The evaporator combines vacuum and heat pump technology to accomplish low temperature distillation. The heat pump supplies heat to evaporate the wastewater and cooling to condense it. Heat is transferred to the unit through multiple shell and tube heat exchangers. Finned air exchangers and variable-speed fans dissipate the heat of compression.

The PACT system comprises the heart of the treatment process. The system combines powdered activated carbon and live microorganisms to treat the wastewater. The activated carbon initially adsorbs the VOCs and other organics. Most of these contaminants become the substrate upon which the microorganisms live. Air is diffused into the system to ensure the mixture remains homogeneous and to provide sufficient oxygen to the microorganisms. With opportunistic access to the contaminants, microorganisms more efficiently oxidize, or destroy, the adsorbed organics.

  

Synthetech's PACT system is a factory-built, sequencing batch reactor unit consisting of an aeration/settling tank, aeration blower, air distribution system and delivery systems for other inputs. Designed to handle a waste stream of about 3,500 gpd of non-process water and 3,500 gpd of evaporator condensate from the process water, the PACT system measures 14 ft. x 12 ft. x 60 ft. and is outfitted with a cover, pH probe and continuous pH adjustment system. It has feed lines for adding wastewater, liquid polymer (aids in fines agglomeration) and microorganism nutrients, a pump for removing sludge and a decantation system for removing treated wastewater. Activated carbon is charged through a port at the top of the system.

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