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Perchlorate treatment by MBR

Ion exchange MBR

The removal of perchlorate by IEMB starts in its physical extraction from the contaminated water stream using an anion exchange membrane (AEM) (Figure 3) (Fox et al. 2014). A driving counterion (usually Cl") is continually fed to the bio-compartment to favor the transport of СЮ4 from the feed water to the bio-compartment via Doiman dialysis. Maximized extraction of C104 can be achieved when the CT is added in excess (Matos et al. 2006a). After the perchlorate passes through

Schematic diagram of perchlorate treatment by IEMB. Modified from Matos et al. (2006b)

Figure 3. Schematic diagram of perchlorate treatment by IEMB. Modified from Matos et al. (2006b).

the positively charged membrane, it is then consumed either by the biofihn developed on the membrane bio-compartment side or by the microbes suspended in the feed medium. Biodegradation of perchlorate takes place primarily on the membrane-biofilm interface rather than in the bulk of the bio-compartment (Ricardo et al. 2012).

Only few literatures are available for the treatment of perchlorate by IEMB (Table 1). Matos et al. (2005) successfully reduced the amount of oxy-anions (C104', N03~, and BrO,“) from synthetically prepared polluted water to values below the lowest recommended levels (25 mg/L of N03“ by EU, 4 pg/L of ClOy by US EPA and 25 pg/L of BrOj by WHO). In a separate study, Matos et al. (2006b) performed three independent experiments to study the mechanism of perchlorate and nitrate removal via Donnan dialysis, biological reduction and IEMB processes. Since commercial ion exchange membrane typically used in IEMB was highly expensive, a cheaper AEM (Excellion 1-200 membrane) was evaluated and compared to the usually employed and costly Neosepta ACS membrane (Matos et al. 2008). Along with perchlorate and nitrate, removal of arsenate and ionic mercury was also studied using various commercial ion exchange membranes (i.e., Neosepta ACS, Ionac MA-3475, Nafion 112, Neosepta CMX) (Velizarov et al. 2005). Ricardo et al. (2012) conducted a kinetic study to assess the effects of the presence of nitrate on the bio-reduction of perchlorate. In the same study, the biofihn growth on the membrane surface was also analyzed for possible biofilm stratification. Above mentioned studies used ethanol as the carbon and energy source of the microbial culture in the bio-compartment. In the studies of Fox et al. (2014, 2016), glycerol was used as carbon substrate instead of ethanol for the biodegradation of high concentrations of perchlorate in synthetic groundwater using IEMB.

Table 1. Summary of the literature on perchlorate treatment using IEMB.

Wastewater

Inoculum

e" donor

Membrane

(Manufacturer)

Operational

conditions*

Results

References

Synthetic

WW(100

pg cio4-/l,

60 mg NOf/L)

Primary inoculum of municipal WWTP

Etlianol

Neosepta ACS (Tokuyama Soda, Japan)

V = 500 mL;

T = 23 ±

1»C; HRT„.

= 1.4-8.3 h; HRTb = 5 h; F/A = 3.1-18.5 Lnvh: Driving counter-ion = 5.84 gNaCl/L

  • • 96.5% CIO у and 99.6% NO3 removal efficiencies.
  • • No bacterial and etlianol contamination found in the treated water.

Matos et al. 2006b

Synthetic WW(100 pg CIO4-/L, 60 mg NOf/L and

200 pg

BrOj/L)*

Enriched

microbial

culture

Etlianol

Neosepta ACS; Excellion™ 1-200

(SnowPure,

USA)

T = 23 ± 1»C; HRTb = 5 h; F/A = 3.1-69.9 Lnvh: Driving counter-ion = 3.55 gNaCl/L

Neosepta ACS

  • • 96% ClOy and 99% N03" removal efficiencies.
  • • No bacterial and etlianol contamination found in the treated water.

Excellion™ 1-200

  • • 85% ClOyand 88% NO3- removal efficiencies
  • • Allowed transport of sulfate and phosphate 10ns to water- compartment.
  • • No bacterial and etlianol contamination found in the treated water.

Matos et al. 2008

Synthetic WW(100 pg C10j7L, 60 mg NO3-/L)

Primary inoculum of municipal WWTP

Etlianol

Neosepta ACS

T = 25 ± PC; HRT„. = 8.3 h; F/A = 3.1 L/ m2h; Driving counter-ion = 5.84 gNaCl/L

  • • Final anion cone, m treated water: 7.0 ± 0.8 pg ClOy/L and 2.8 ± 0.5 mg NOj/L.
  • • NOj reduction was unaffected but ClOy reduction rate decreased by 10% under ammonia limitation.

Ricardo et al. 2012

Synthetic GW (250 mg ClOy/L)

Enriched culture from soil sample ofClOj- contanunated site

Glycerol

Neosepta ACS

F/A*, = 0.66 mL/cm2h; F/

Ab = 0.13-0.16 mL/cm2h; HRT„. = 12 h; HRTb = 100- 125 h, T„. = 26-29°C; Tb = 25°C; Driving counter-ion =

5 86 gNaCl/L

  • • Increase in initial ClOy cone, decreased its removal efficiency in the feed water- compartment.
  • • 99% ClOy removal efficiency in the bio- compartment.

Fox et al. 2014

Synthetic GW (1 mM ClOy, 0,1-4 mM NOf)

Enriched culture from soil sample ofClOy contammated site

Glycerol

Neosepta ACS

F/Av = 0.62 mL/cnFh; F/

Ab = 0.13-0.19 mL'cm2h; HRT„. = 15h;HRTb = 125-83 h;Tw = 26-27°C;Tb = 25°C

• Over 99% biodegradation efficiency for both ClOy and NO3 in the bio-compartment.

Fox et al. 2016

# All reactors used are in continuous mode; * Bromate was evaluated only in Donnan dialysis studies and not in IEMB (Y, reactor vol.; HRT, hydraulic retention time; w, water-compartment; b, bio-compartment; T, temperature; F/A, water flow rate per membrane area); GW, groundwater; WW, wastewater; WWTP, wastewater treatment plant.

 
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