Blackwater is water that has been mixed with waste from the toilet. Because of the potential for contamination by pathogens and grease, water from kitchens and dishwashers should be excluded from grey water and considered as blackwater. Each wastewater type must be treated differently and can be used in various ways. Blackwater requires biological or chemical treatment and disinfection before reuse.

Objective :

  1. To check the effect of bio-beds for treatment of black water.
  2. To compare the three systems used for treatment –
    • Flood and drain system
    • System with bubbler
    • system without bubbler

06/04/2022 – 07/04/2022

Collection of blackwater and selection of plants

fig.1 Collected blackwater and selected plants

Determination of COD (Chemical Oxygen Demand)

Reagents –

  1. Potassium dichromate (K2Cr2O7).
  2. Mercuric sulphate (HgSO4)
  3. Sulfuric acid (H2SO4)
  4. Ferrous ammonium sulphate (FAS)
  5. Ferron indicator
  6. Potassium hydrogen phosphate (KHP)
  7. 250 ml Erlenmeyer flask
  8. Reflux condenser
  9. COD tubes
  10. Measuring cylinder
  11. Analytical balance
  12. COD tube stands

Procedure –

  1. Take 0.4 gm. HgSo4 (mercuric sulphate) in COD tubes.
  2. Add 20 ml sample in each COD tube (20 ml water sample, 20 ml KHP solution).
  3. Add 20 ml distilled water in each COD tube.
  4. Add stones (crush on beads) 1 or 2 pieces.
  5. Add 10 ml (0.25 N) K2Cr2O7 Potassium dichromate solutions.
  6. Add 30 ml conc sulfuric acid slowly along with swirling.
  7. If the solution turns green add more known quantities of K2Cr2O7 solution.
  8. Kept COD tubes in COD apparatus to digest the sample.
  9. Attach condenser & set 150 Degree Celsius temperature.
  10. Kept for 2 hours filled COD tubes in COD apparatus for 150 degree Celsius.
  11. After 2 hours switch off & remove COD tubes & cooled sample for room temperature.
  12. Take the above sample in a conical flask. Add 150 ml distilled water.
  13. Titration: – Titrate above solution with 0.1 N FAS (ferrous ammonium sulphate) solution by using Ferron indicator (add 3-4 drops). The end point of this titration is blue green to reddish brown.

fig. 2- Determination of COD

Formula of COD

COD = {(a-b) X N X 8000}/ml of sample solution
Where,

  1. A-Reading blank solution.
  2. B-Reading with sample solutions
  3. N- Normality of FAS solution

Dilution factor = ( ml of sample + distilled water )/ ml of sample

Calculation of COD

SampleReadingsCOD (mg/lit)
Blank10.4–
KPH4.6529
Black water8.12340
Grey water8.9612
Table no. 1 Calculation of COD

SampleReadingsCOD (mg/lit)
Blank10.1–
Tap water9.561.2
Blackwater8.51632
Greywater9.4714
Table no. 2 calculation of COD

06/04/2022-10/04/2022

Collection of material

The material required for setup of systems for treatment of black water is as follows:

  1. Buckets
  2. Bubbler
  3. Stand
  4. Lateral
  5. T-joint
  6. Elbow
  7. Grommet
  8. wires
  9. Timer
  10. Sub-mersible pump 18 watt
  11. ARDUINO

11/04/2022-25/04/2022

Bill of material

Bill-of-material-BWSDownload

The set-up of two systems i.e. bubbling and without bubbling is done.

  • Bubbling system : In bubbling system, two buckets are used in which 17 litres of black water is filled. In first bucket, water hyacinth is planted and in second indian shot is planted. bubblers are used for aeration.
  • Without bubbling system: This system is same as bubbling system. Only difference is bubblers are not used.
Fig. 3 Set-up of bubbling and without bubbling systems
Fig. 4 Process flowchart for setup of Bubbling and without Bubbling system

Flood and drain system: In this system, two buckets and two reservoirs are used. Buckets are to be placed on stand and reservoir will be under the stand.The bucket in which Indian shot is to be planted is connected with drip pipe at bottom. Hence, the black water will drain out from bottom. And the bucket in which water hyacinth is to be planted is connected with drip pipe at a height of 5 cm from side. This drip pipes are connected with submersible pumps. A timer is to be used for this system. Both pumps will operate on 1 timer.

Fig. 5Set-up of flood and drain system
Fig. 6 Process flowchart for setup of Flood and drain system.

3D CAD Designing of blackwater system

3D Design of blackwater system

19/04/2022 – 24/04/2022

ARDUINO set-up of blackwater system:

Block diagram:

Fig. 7 Block diagram for connection of pump
Fig.8 Connection diagram for pump

ARDUINO CODE of blackwater system :

aurdinoDownload

25/04/2022

Determined COD

without bubblerwith bubblerflood and drain
Initial COD (day 1) (mg/lit)234023402340
Initial COD (day 1) (mg/lit)163216321632
After 17 days (mg/lit)183021421326
Table no. 3 COD Readings

COD is decreased in every system. But maximum decrease in COD is found in flood and drain system compared to others.

Fig. 9 Plants in black water system

30/04/2022

Re-setup of black water system

The three systems of black water were setup on different times and the results cannot be compared effectively. So, the systems are set again at same time. For this, the black water in previous systems is mixed and used.

29/04/2022

Determined COD:

Without bubblerWith bubblerFlood and drain
Initial COD (mg/lit)918918918
Table no.4 COD readings

29/04/2022 – 03/05/2022

Determined COD

Without bubbler
(Water hyacinth)		Without bubbler
(Indian shot)		With bubbler
(Water hyacinth)		With bubbler
(Indian shot)		Flood and drain
(Water hyacinth)		Flood and drain
(Indian shot)
Initial COD (mg/lit)
30/04/2022		918918918918918918
03/05/2022714714714510510306
Table no.5 COD readings

Percentage losses in COD

Without bubbler
(Water hyacinth)		Without bubbler
(Indian shot)		With bubbler
(Water hyacinth)		With bubbler
(Indian shot)		Flood and drain
(Water hyacinth)		Flood and drain
(Indian shot)
03/05/202222.2%22.2%22.2%44.4%44.4%66.6%
06/05/202233.3%44.4%44.4%55.5%66.6%77.7%
Table no. 6 % losses in COD

From above table, it is seen that flood and drain system with Indian shot gives highest decrease in COD comparing with all systems.

10/05/2022

Trial 2nd

The three systems of black water were setup on different times and the results cannot be compared effectively. So, the systems are set again at same time. For this, the black water in previous systems is mixed and used.

Determined COD

29/04/2022 – 31/05/2022

Without bubbler
(Water hyacinth)		Without bubbler
(Indian shot)		With bubbler
(Water hyacinth)		With bubbler
(Indian shot)		Flood and drain
(Water hyacinth)		Flood and drain
(Indian shot)
Initial COD (mg/lit)
30/04/2022		918918918918918918
03/05/2022714714714510510306
06/05/2022612510510408306204
Table no.4 COD readings of 2nd trial

For 3rd trial, black water is collected again and distributed in system on 10/05/2022. The COD of this water is 2244 mg/lit.

Without bubbler
(Water hyacinth)		Without bubbler
(Canna Indica)		With bubbler
(Water hyacinth)		With bubbler
(Canna Indica)		Flood and drain
(Water hyacinth)		Flood and drain
(Canna Indica)
Initial COD (mg/lit)
11/05/2022		224422442244224422442244
14/05/2022219321932193214220401836
17/05/2022204018361785142815301224
20/05/202219381632142811221122918
23/05/2022183613261224918816408
26/05/202217851122918612510204
Table no. 6 COD readings of 3rd trial

From the observations of trial taken, it is seen that the sustainability of water hyacinth is less in black water. It starts to wilt in 4-5 days. So in 4th trial, it is decided to dilute the black water with tap water. For dilution following calculation is done:

Fig. 10 Calculation for dilution
Without bubbler
(Water hyacinth)		Without bubbler
(Canna Indica)		With bubbler
(Water hyacinth)		With bubbler
(Canna Indica)		Flood and drain
(Water hyacinth)		Flood and drain
(Water hyacinth)
28/05/2022224422442244224422442244
31/05/202217851122918612510204
Table no. 6 COD readings of 4th trial
Fig 11 Plants in 1) Flood and drain & 2) with bubbling and 3)without bubbling

Result

Without bubbler
(Water Hyacinth)		Without bubbler
(Canna Indica)		With bubbler
(Water Hyacinth)		With bubbler
(Canna Indica)		Flood and drain
(Water Hyacinth)		Flood and drain
(Canna Indica)
% losses in COD IN 15 days20%50%59%72%77%90%
Table no. 7

Conclusion

  1. In black water, water hyacinth was sustaining in starting period but after 4-5 days it started to wilt which can be seen from the figure 18. The growth of Canna Indica is better than water hyacinth. The roots were growing 
  2. COD is decreased in every system. But maximum decrease in COD is found in flood and drain system compared to others.
  3. The system with Canna Indica plants shows better results. The COD reduces more in system with Canna Indica.