Process Chemistry and Laboratory Analysis

Process Chemistry and Laboratory Analysis
Filter presses with on-demand chlorine dioxide system save disposal expenses, decrease odor

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  Filter presses with on-demand chlorine dioxide system save disposal expenses, decrease odor

Problem
The City of Martinsville, Va., once paid more than $300,000 a year for biosolids handling and $180,000 more for electricity for aerobic digestion and belt press dewatering. Filtered biosolids averaged 17 percent solids. Plant operators wanted a more efficient method that also addressed odor issues.

Solution
Operators installed two  HyPack Filter Presses manufactured by Beckart Environmental, automated with a programmable logic controller to minimize operator time. Each filter press processes 125 cubic feet per day. Beckart also supplied a system to allow operators to make chlorine dioxide on demand to address odors.

Result
The system increased solids content to 33 percent, reducing hauling and handling costs by about 50 percent and saving $160,000 a year. Electricity costs to run two 200 hp blowers associated with the old system of aerobic digestion with belt presses around the clock were nearly eliminated. Operators also reported satisfaction with the odor-control system. 262/656-7680; www.beckart.com.

  Membrane cleaner provides RO-quality water for ethanol distiller

Problem
The City of Fargo (N.D.) Wastewater Treatment Plant has an auxiliary effluent reuse facility (ERF) to produce 1 mgd of reverse-osmosis-quality water for Tharaldson Ethanol, a corn-to-ethanol distiller. Particularly in cold weather, the ERF experienced biological fouling of the PVDF polymer RO membranes and significantly increased trans-membrane pressure (TMP). This condition had to be resolved quickly to ensure a plentiful supply of RO water.

Solution
To determine the optimal membrane cleaning regimen, the Fargo plant team systematically evaluated 20 cleaners and hundreds of combinations and concentrations, including commonly used commodities and many formulated membrane cleaners. They selected International Products Corp.’s MICRO-90 for working effectively without phosphates, silicates and strong alkalis, at a membrane-compatible pH of 9.5 and at a 0.3 percent concentration.

Result
The ERF has used MICRO-90 since October 2010. Some of the original PVDF membranes are still in use and continue to see significant TMP drops after cleaning. The Fargo ERF design engineers have recommended the cleaner to other similar ERFs nationwide. 609/386-8770; www.ipcol.com.

  Solution improves winter sludge settling at treatment plant

Problem
The Wentzville (Mo.) Wastewater Treatment Plant faced increasing problems operating an undersized aerobic digester in the middle of winter, when volatile solids destruction is low and frozen soils do not allow land application of biosolids. The aeration basins were operated at the maximum mixed liquor suspended solids level, the clarifier sludge blankets were maxed out, the drying beds were full and there was no room for waste sludge. Filaments began to grow, foam increased, and effluent BOD and TSS suffered. The operators wanted better settling sludge, increased decant and more space for waste sludge within the existing digesters.

Solution
After six months of trials, plant operators discovered that BIO ENERGIZER from Probiotic Solutions could increase biomass metabolism and destroy sludge, accelerating the bacteria’s rate of endogenous respiration by improving cell wall permeability. 

Result
The percent of volatile solids destruction increased by a total of 43 percent to 85 percent in 27 weeks, and decants were improved. 800/961-1220; www.probiotic.com.

  Plant tests reinforce peracetic acid’s high success rate in wastewater treatment

Problem
A wastewater treatment plant in Steubenville, Ohio, needed a cost-effective disinfection method that would not generate chlorinated byproducts.

Solution
Solvay Chemicals conducted independent plant-scale trials using Proxitane WW-12 peracetic acid (PAA). The tests were completed over a little more than one month. PAA, a rapidly acting disinfectant, does not generate harmful disinfection byproducts even if overdosed. The dosing system can be economically retrofitted or work in series with an existing disinfection system. The plant was operating at 5 to 8 mgd, with a design capacity of 13.5 mgd.

Result
The test was successful. PAA dosage never exceeded 1.5 ppm, and the residual chlorine averaged 0.4 ppm, never exceeding 1 ppm. PAA feed was flow-paced, CBOD remained constant and pathogen control was always within the permit limits. 800/765-8292; www.solvaychemicals.us.



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