This program is supported by Award Number P42ES017198 from the National Institute of

Environmental Health Sciences.

northeastern.edu/protect

The preterm birth rate in Puerto Rico is 17.7% of live births. At 50% above the U.S. average, it is the highest rate of any U.S. jurisdiction, below only Malawi (18.1%) globally, a discrepancy that is not explained by other socio-cultural factors. Our investigations suggest that the higher preterm birth rates in Puerto Rico cannot be explained by changes in obstetric practices, and that there is compelling preliminary evidence that exposure to hazardous chemicals contributes to preterm birth. Puerto Rico has 16 active Superfund sites and 200+ hazardous waste sites. Risk of exposure to contamination is high as many of these sites are unlined landfills that overlie karst aquifers which present highly susceptible pathways for exposure to contamination. PROTECT is testing the hypothesis that exposure to hazardous chemicals contributes to the high rate of preterm birth in Puerto Rico. The Center brings together multidisciplinary researchers to study the transport, exposure, health impact and remediation of contaminants, with particular attention to chlorinated solvents and phthalates commonly found at Superfund sites, as both suspect and model agents in the high preterm birth rates in Puerto Rico.

PROTECT SIGNIFICANCE AND APPROACH

As part of the PROTECT Center, Project 5 is developing solar-powered technologies to treat a variety of contaminants, focusing particularly on trichloroethylene (TCE), a common Superfund contaminant in groundwater for groundwater treatment use solar panels to generate a low-level direct current (DC) through electrodes in wells which enables manipulation of groundwater chemistry through electrolysis to create conditions favorable for either reduction or oxidation of the contaminants. Development of an electrochemical reactor within the aquifer for the sustained, solar-powered electrolysis is the first step in development of solar-powered electrochemical technologies.

PRF (cycles h-1) ON/OFF intervals duration (min) Removal rate (%)

6 5/5 50.3 10 3/3 56.3 15 2/2 69.0

30 1/1 34.7 90 0.3/0.3 23.4

TCE removal efficacy was calculated as: where C0 is the initial TCE concentration (mg L-1) and Ct is TCE concentration at defined time during treatment (mg L-1).

Current intensity: 60 mA; Flow velocity: 3 mL/min; Inter-electrode distance: 2.5 cm; Solution: 0.172 g/L CaSO4; 0.413 g/L NaHCO3; 5.3 mg/L TCE. Treatment duration: 60 min Electrodes type: Ti/MMO (Ti/IrO2–Ta2O5) Pd catalyst: 2 g Pd/alumina

ELECTROCHEMICAL REMOVAL OF TRICHLOROETHYLENE FROM GROUNDWATER: POLARITY REVERSAL FOR SUSTAINABLE TREATMENT

Ljiljana Rajic, Noushin Fallahpour, Ali Ciblak, Akram Alshawabkeh

Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, MA 02115, United States

The overall TCE removal rate is given in Table. TCE removal up to 69% is achieved by optimizing the polarity reversal frequency (15 cycles h-1). It was found that no H2O2 is produced in Pd vicinity. ORP and pH value of the effluent changed negligibly during experiments with polarity reversal. The removal mechanism is not supported by Pd catalyst. The interval duration during polarity reversal influences: the processes involved in removal (oxidation or reduction); the amount of charge evolved in the reaction; time for the reaction and the amount of target specie that interacts with the electrode.

RESULTS

Polarity reversal was calculated as: where PRF is polarity reversal frequency (cycles h-1), t0 is duration of the original electrode polarity (min) and tr is duration of the reversed electrode polarity (min).

Here we present the possibility of electrode polarity reversal application for electrochemical treatment of TCE contaminated groundwater from limestone aquifer. We used flow-through system with two electrodes in the presence of Pd catalyst. Pd can catalyze the composition of H2O2 and its decomposition in weak acidic conditions to a strong oxidizing •OH radical. pH profile can be controlled by the optimization of electrode original and reversed polarity duration. Both H2 and O2 could generate in the Pd catalyst vicinity when changing the electrode polarity.

Proposed MECHANISM

Cat

hode

Anode

TCE

H2O

H2O

H2

O2 Pd

H

H

Reduction Products

H2O2

•OH

Fe2+

TCE

CO2

•OH

CO2

0 10 20 40 60

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

C/Co

Time (min)

Control 6 10 15 30 90

PROTECT: Puerto Rico Testsite for Exploring Contamination Threats – NIEHS SRP P42 Center