The District of Columbia Water and Sewer Authority provides drinking water, sewage collection and sewage treatment in Washington, D.C., USA. DC Water also provides wholesale wastewater treatment services to several adjoining municipalities in Maryland and Virginia. In addition, DC Water provides maintenance and repair of more than 9,000 public fire hydrants on behalf of the District of Columbia. DC Water was created in 1996, when the District Government and the U.S. federal government established it as an independent authority of the District government.DC Water provides more than 600,000 residents, 16.6 million annual visitors and 700,000 people who are employed in the District of Columbia with water, sewage and wastewater treatment. DC Water also provides wholesale wastewater treatment for 1.6 million people in Montgomery and Prince George’s counties in Maryland, and Fairfax and Loudoun counties in Virginia.In 2010, under new leadership, the Authority underwent a rebranding effort. The rebranding included a new logo, new color palette, and a new name. Since its inception, the Authority had been doing business as DC Water. The legal name remains the District of Columbia Water and Sewer Authority. Wikipedia.
Fang J.,District of Columbia Water and Sewer Authority |
Deng B.,University of Missouri
Journal of Membrane Science | Year: 2014
Nanofiltration (NF) membranes, DK and DL, were characterized by attenuated total reflection-Fourier transform infrared spectroscopy, surface charge titration, pore size determination and salt rejection. The results showed both membranes have amide I and carbonyl groups on their surfaces, and have the same basic structure of polyamide layer sitting on the top of a polysulfone layer. The DK membrane carries more negative charges in the entire pH range investigated. Arsenate rejections by the NF membranes were evaluated with a crossflow test setup. The effects of pH, ionic strength, operating pressure, arsenate initial concentration on the membrane performance were investigated. Mass transfer coefficients of the membranes were determined experimentally. The Donann Steric Pore Model and concentration polarization film theory were applied to calculate the arsenic rejection rate. The rejection mechanism was interpreted by calculating the contributions of convection, diffusion, and electrostatic migration to arsenic transport through the membranes. The calculated results showed that the contribution of diffusive transport dominated at low flux, and convection and electromigrative transport, especially the latter, play an increasingly important role at a high flux. © 2013 Elsevier B.V.
Bevacqua C.E.,University of Maryland College Park |
Rice C.P.,Beltsville Agricultural Research Center |
Torrents A.,University of Maryland College Park |
Ramirez M.,District of Columbia Water and Sewer Authority
Science of the Total Environment | Year: 2011
Steroid hormones can act as potent endocrine disruptors when released into the environment. The main sources of these chemicals are thought to be wastewater treatment plant discharges and waste from animal feeding operations. While these compounds have frequently been found in wastewater effluents, few studies have investigated biosolids or manure, which are routinely land applied, as potential sources. This study assessed the potential environmental contribution of steroid hormones from biosolids and chicken litter. Hormone concentrations in samples of limed biosolids collected at a waste treatment plant over a four year period ranged from < 2.5 to 21.7. ng/g dry weight for estrone (E1) and < 2.5 to 470. ng/g dry weight for progesterone. Chicken litter from 12 mid-Atlantic farms had averages of 41.4. ng/g dry weight E1, 63.4. ng/g dry weight progesterone, and 19.2. ng/g dry weight E1-sulfate (E1-S). Other analytes studied were 17β-estradiol (E2), estriol (E3), 17β-ethinylestradiol (EE2), testosterone, E2-3-sulfate (E2-3-S), and E2-17-sulfate (E2-17-3). © 2011 Elsevier B.V.
Wu C.,Beijing Forestry University |
Zhang G.,Renmin University of China |
Zhang P.,Beijing Forestry University |
Chang C.-C.,District of Columbia Water and Sewer Authority |
Chang C.-C.,University of Maryland Baltimore County
Chemical Engineering Journal | Year: 2014
Sludge disintegration destroys the sludge floc structure and releases the extracellular polymeric substances (EPS) and cell contents into the liquid phase, to enhance the sludge anaerobic digestion. Potential benefits of potassium permanganate (KMnO4) disintegrating excess sludge were investigated in this paper. Sludge disintegration feasibility was analyzed with soluble chemical oxygen demand (SCOD) increase in supernatant. Sludge disintegration mechanisms were explored with analyzing the change of particle size, EPS, oxidation reduction potential (ORP) and Mn state. Sludge disintegration process was optimized through analyzing disintegration degree (DDCOD). Results showed that KMnO4 effectively disintegrated the excess sludge with a SCOD increase of 3473% and more than 97% of Mn transferred into the solid phase. A slow decrease in particle size was observed. EPS was efficiently released into supernatant, and supernatant proteins and polysaccharides increased by 490% and 141%, respectively. Loosely bound EPS increased by 498%, which was much higher than slime EPS and tightly bound EPS. The main mechanism of sludge disintegration was KMnO4 oxidation. After sludge oxidation, KMnO4 mainly transferred to the sludge solids with the states of MnO2 and Mn3O4, and a state of KxMnO4 also existed in the solids. Optimization experiments showed that suitable reaction time was 30min, and KMnO4/sludge solid mass ratio was the most important factor and its optimal value was 0.1 with a stable DDCOD of about 34%. © 2013 Elsevier B.V.
Andrade N.A.,University of Maryland University College |
Mcconnell L.L.,U.S. Department of Agriculture |
Torrents A.,University of Maryland University College |
Ramirez M.,District of Columbia Water and Sewer Authority
Journal of Agricultural and Food Chemistry | Year: 2010
This study examines polybrominated diphenyl ethers (PBDE) levels, trends in biosolids from a wastewater treatment plant, and evaluates potential factors governing PBDE concentrations and the fate in agricultural soils fertilized by biosolids. The mean concentration of the most abundant PBDE congeners in biosolids (∑BDE-47, BDE-99, and BDE-209) generated by one wastewater treatment plant was 1250 ± 134 μg/kg d.w. with no significant change in concentration over 32 months (n = 15). In surface soil samples from the Mid-Atlantic region, average PBDE concentrations in soil from fields receiving no biosolids (5.01 ± 3.01 μg/kg d.w.) were 3 times lower than fields receiving one application (15.2 ±10.2 μg/kg d.w.) and 10 times lower than fields that had received multiple applications (53.0 ± 41.7 μg/kg d.w.). The cumulative biosolids application rate and soil organic carbon were correlated with concentrations and persistence of PBDEs in soil. A model to predict PBDE concentrations in soil after single or multiple biosolids applications provides estimates which fall within a factor of 2 of observed values. © 2010 American Chemical Society.
Lozano N.,University of Maryland University College |
Rice C.P.,U.S. Department of Agriculture |
Ramirez M.,District of Columbia Water and Sewer Authority |
Torrents A.,University of Maryland University College
Environmental Pollution | Year: 2012
This study investigates the persistence of Triclosan (TCS), and its degradation product, Methyltriclosan (MeTCS), after land application of biosolids to an experimental agricultural plot under both till and no till. Surface soil samples (n = 40) were collected several times over a three years period and sieved to remove biosolids. Concentration of TCS in the soil gradually increased with maximum levels of 63.7 ± 14.1 ng g -1 dry wt., far below the predicted maximum concentration of 307.5 ng g -1 dry wt. TCS disappearance corresponded with MeTCS appearance, suggesting in situ formation. Our results suggest that soil incorporation and degradation processes are taking place simultaneously and that TCS background levels are achieved within two years. TCS half-life (t 0.5) was determined as 104 d and MeTCS t 0.5, which was more persistent than TCS, was estimated at 443 d. © 2011 Elsevier Ltd. All rights reserved.