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Removal of Nutrients from Wastewater using Biochar. Tao Xie a , Krishna R. Reddy b , Chengwen Wang a a School of Environment, Tsinghua University, Beijing (100084), China b Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA. Outline.

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removal of nutrients from wastewater using biochar

Removal of Nutrients from Wastewater using Biochar

Tao Xiea, Krishna R. Reddyb, Chengwen Wanga

a School of Environment, Tsinghua University, Beijing (100084), China

b Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA

outline
Outline
  • 1. Introduction
  • 2. Objective
  • 3. Materials and Methods
  • 4. Preliminary Results
  • 5. Conclusions

School of Environment, Tsinghua Univ.

1 1 urine separating system
1.1 Urine separating system

Urine separation

  • Collection of wastewater in segregated streams is one of the new concepts in wastewater treatment.
  • One such stream is yellow water which is mainly human urine (Beler-Baykal et al. 2009).
  • About 80 % of the nitrogen, 50 % of the phosphorus and 50 - 60 % of the potassium from domestic wastewater come from the urine (Ban and Dave 2004).
  • Relieve the burden of WWTPs.
  • Reduce eutrophication in freshwater.
  • Nutrients reuse in agricultural fields.

Fig. 1. Sketch of source separation and nutrient recovery system

School of Environment, Tsinghua Univ.

1 1 urine separating system1
1.1 Urine separating system

Application

  • Urine separating system in Beijing Olympic Forest Park

School of Environment, Tsinghua Univ.

1 2 nutrients recovery from the separated urine
1.2 Nutrients recovery from the separated urine

Obstacles for using urine directly

  • The main problem is the storage, transport and spreading of large amounts of urine (Ganrot et al. 2007).
  • Its salinity is too high for agricultural and landscape purposes (Beler-Baykal et al. 2011).
  • The loss of nitrogen through ammonia evaporation is significant during storage and spreading (Ban and Dave 2004).

Indirect use

  • Struvite precipitation
  • Adsorption/ion exchange
  • Can also be combined together
  • Freezing-thawing

School of Environment, Tsinghua Univ.

1 2 nutrients recovery from the separated urine1
1.2 Nutrients recovery from the separated urine

(MAP)(MgNH4PO4·6H2O)

  • Struvite precipitation
  • Adsorption/ion exchange

Fig. SEM photo of struvite

  • The ion exchange properties of zeolites, especially of the NH4+ specific clinoptilolite are well documented, which can be used for nitrogen recovery (Ban and Dave 2004; Leung et al. 2007).
  • Freezing-thawing
  • It has a positive effect on N reduction (Ganrot et al. 2007).

Ying Jin et al, Water Research, 2009, 43: 3493-3502.

School of Environment, Tsinghua Univ.

1 3 application of biochar as adsorbent
1.3 Application of biochar as adsorbent
  • Struvite crystallization and zeolite adsorption are usually combined to achieve better recovery efficiency (Ban and Dave 2004).
  • However, the main problem is the application after crystallization and adsorption, which required ammonium to be released from exhausted zeolite through desorption (Beler-Baykal et al. 2011).
  • The lower recovery efficiency of desorption can affect the final recovery efficiency (Beler-Baykal et al. 2004).
  • Biochar can be considered to replace the zeolite as nutrient adsorbent since it can be used directly in agricultural soils without desorption process.

School of Environment, Tsinghua Univ.

outline1
Outline
  • 1. Introduction
  • 2. Objective
  • 3. Materials and Methods
  • 4. Preliminary Results
  • 5. Conclusions

School of Environment, Tsinghua Univ.

2 objective
2. Objective

1

2

3

  • To test the potential of biochar as an adsorbent for nutrients including nitrogen, phosphorus and potassium.
  • To optimize the recovery of P and N from artificial urine through struvite precipitation via MgO addition and NH4+ and K+ adsorption by biochar.
  • To determine the fertilizing effect of the struvite and exhausted biochar on agricultural soil and plant.

School of Environment, Tsinghua Univ.

outline2
Outline
  • 1. Introduction
  • 2. Objective
  • 3. Materials and Methods
  • 4. Preliminary Results
  • 5. Conclusions

School of Environment, Tsinghua Univ.

3 1 materials
3.1 Materials
  • Artificial urine

Table 1 Properties of fresh and stored human urine(Beler-Baykal et al. 2009)

Table 2 Composition of artificial urine solution in deionised water (Udert, 2003)

School of Environment, Tsinghua Univ.

3 1 materials1
3.1 Materials
  • Biochar

For NH4+ adsorption

Table 3 Properties of biochar used in the study

  • Magnesium oxide

For PO43- adsorption and struvite crystallization

School of Environment, Tsinghua Univ.

3 2 methods
3.2 Methods
  • Nutrients adsorption

5g biochar in 100mL artificial urine, stir for 24h

Pass the sample through filter

Test pH and nutrients in the solution

School of Environment, Tsinghua Univ.

3 2 methods1
3.2 Methods
  • Stuvite crystallization and biochar adsorption
  • 5g biochar and 0.5g MgO in 100mL artificial urine, stir for 24h
  • Change the ratio of biochar to MgO and pH to get optimal result

School of Environment, Tsinghua Univ.

outline3
Outline
  • 1. Introduction
  • 2. Objective
  • 3. Materials and Methods
  • 4. Preliminary Results
  • 5. Conclusions

School of Environment, Tsinghua Univ.

4 1 nutrient recovery process
4.1 Nutrient recovery process

The addition of MgO resulted in the rapid formation of small crystals.

Needle-shaped crystals became visible on the surface of biochar.

After filtration, biochar with a fine crystalline white powder was obtained.

Biochar

MgO

Biocahr+MgO

School of Environment, Tsinghua Univ.

4 1 nutrient recovery process1
4.1 Nutrient recovery process

With the addition of biochar, N and P can be removed. The adsorption effects differed with different biochar types, ranged between 17.5 % to 36.4 % of N removal, as well as 4.1 % to 19.7 % of P removal.

With the addition of MgO, mainly P was removed. More than 92.2 % of P and 12.7 % of N was settled.

Biochar

MgO

Biocahr+MgO

With the combination of biochar and MgO, nutrient removal efficiency increased significantly, especially for the P removal, from around 10 % with only biochar increased to more than 98 % with MgO addition.

School of Environment, Tsinghua Univ.

4 2 biochar types
4.2 Biochar types

Fig. 2. Nutrient removal by different types of biochars with MgO addition

BS seemed to show greatest adsorption capacity of N and P, which was 52.9 mg N g-1biochar and 2.52 mg P g-1biochar, separately.

BS had the lowest zeta potential, which indicated that its surface was most negatively charged and more likely to sorb positively charged ions such as ammonium.

4 3 ratio of biochar and mgo
4.3 Ratio of biochar and MgO

Fig. 3. Nutrient removal with different ratio of biochar and MgO additions:

(a) N removal

The maximum reduction of N, from 7.26 g L-1 to 3.82 g L-1, was found with the addition of MgO(1.0 g) and biochar (10 g).

To improve uptake, higher amounts of biochars can be used, but it is also a matter of cost efficiency.

4 3 ratio of biochar and mgo1
4.3 Ratio of biochar and MgO

Fig. 3. Nutrient removal with different ratio of biochar and MgO additions:

(b) P removal

Removal efficiency of 90 % was achieved with the addition of 0.5 g MgO and could be increased to more than 99 % with the addition of 1.0 g.

4 4 ph
4.4 pH

Fig. 4. Nutrient removal at different pH values

Some by-products might be formed in the sediments with pH higher than 10.

The optimum pH was between 8.1 and 9.2, usually near 8.7, as the struvite precipitation potential reached maximum while precipitation of undesired by-products was minimized.

outline4
Outline
  • 1. Introduction
  • 2. Objective
  • 3. Materials and Methods
  • 4. Preliminary Results
  • 5. Conclusions

School of Environment, Tsinghua Univ.

5 conclusions
5. Conclusions

1

2

3

  • Most of the N and P from urine can be recovered as solids through combined adsorption (by biochar addition) and precipitation (by MgO addition).
  • Four types of biochars derived from woody biomass were applied in the batch experiments and the one with lower zeta potential was selected for later studies due to its higher adsorption capacity.
  • The recovery of both N and P from artificial urine was affected by the combination of MgO and biochar and mixing pH conditions.
  • Maximum combined recovery of N and P occurred at addition of 1.0 g MgO and 10 g biochar per 100 mL artificial urine at pH ranged from 8 to 10.

School of Environment, Tsinghua Univ.

5 conclusions1
5. Conclusions

4

  • The results obtained have given positive preliminary indications that recovery of N and P from artificial urine with biochar and MgO could be possible.
  • The mixture of struvite and environmental friendly adsorbent (biochar) has good nutrient qualities and can be used as potential fertilizer.

School of Environment, Tsinghua Univ.

thanks

Thanks!

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