DEVELOPING A PILOT SCALE CONSTRUCTED WETLAND FOR

TREATMENT OF DOMESTIC SEWAGE

Nischay.N B.E.(CIVIL)., M.Tech. ,IGBC-AP.

,

What is a Wetland???• A wetland is a land area that is saturated  with water , either

permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem .

• The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation

of aquatic plants , adapted to the unique hydric soil.

Wetland

Natural

Constructed

.

Natural Wetland • Natural wetland systems have often been described as the

“earth’s kidneys” because they filter pollutants from water that flows through on its way to receiving lakes , streams and oceans.

Constructed Wetlands• Constructed wetlands are artificial wastewater treatment

systems consisting of shallow (usually less than 1 m deep) ponds or channels which have been planted with aquatic plants, and which rely upon natural microbial, biological, physical and chemical processes to treat wastewater.

• They typically have impervious clay or synthetic liners, and engineered structures to control the flow direction, liquid detention time and water level

LOCATION : JAKKUR LAKE

Constructed Wetland• By various such process chemicals are considerably

removed or settled and clean water is drawn. These chemicals include Nitrogen, Ammonia, Phosphorous and pathogens.

• Constructed wetlands are most economical as compared to conventional treatment units which needs more energy for its process and this method require cheaper materials.

LOCATION: NARSIPURA

TYPES

Constructed Wetland

Surface Flow

Sub Surface Flow

Vertical Flow

Up Flow

Down Flow

Horizontal Flow

Objectives• Generally the waste water generated in the houses is released to

the waste water carriage system. However, it is very difficult to treat the waste water generated in a centralised way in Bangalore city.

• Hence, there is a necessity of decentralised waste water treatment facilities at household level.Necessity of constructed wetlands is to achieve the following

1.To treat domestic waste water generated in the houses at household level using constructed wetland

2. To test the quality of treated waste by using constructed wetlands for other beneficial uses (recycling of treated waste water).

Removal mechanism

• Organic matter : Aerobic microbial degradation Anaerobic microbial degradation

• Suspended solids: Sedimentation Filtration

• Pathogens : Sedimentation Filtration Natural die-off Predation UV radiation

Removal mechanism

• Nitrogen : Nitrification and denitrification Plant uptake Matrix adsorption

• Phosphorus : Matrix absorption Plant uptake

• Metals : Adsorption and cation exchange Complexation Precipitation

Plant uptake Microbial oxidation/reduction

Practical Approach

• Construction of “Horizontal subsurface flow constructed wetland”.

Methodology• In this experimental set up of buckets with different sizes and

dimensions will be used. • The vertical buckets as holding tank (Inlet) will be used to hold the waste water The water storing capacity of tank will be 50 litres.• A rectangular tub of size 62 cm length and height 35 cm having suitable outlet.

Methodology

• The vertical pipe will be placed above the tub for distribution of water . Plastic cans will be used for the collection of treated water.

• Treated water samples will be collected and analyzed in laboratory.

• The Angular Horizontal Subsurface Flow constructed wetland will be prepared as follows:Three layers of support bed in constructed wetland will be prepared with coarse aggregate , Sand and Garden soil.

Methodology• Coarse aggregate of 20 kg total weight will be used for

making bottom layer of 10 cm height • Followed by medium sized sand amounting total to 15 kg will

be added to form a middle layer of 10 cm height and small size, sieved 6 kg of soil to form upper layer of 10 cm height will be used in construction of bed.

• Selective healthy, small, young, locally available plant will be transplanted into the bed .

• The rectangular tub with plant bed will be provided with 10 degree slope and kept in the slanting position.

• Inlet flow and outlet flow of wastewater will be adjusted to maintain Hydraulic retention Time (HRT) of 7 days

Work done as per schedule

PROJECT LOCATION : MALLATHALLI

STARTED ON: 12th MARCH

STEP:1 PROVIDING SLOPE

Slope :1:10

Layer 1: Coarse Aggregates

1st layer : Gravel stones Size between >20mm & <40mm

Depth of layer: 100mm

Layer 2: Fine Aggregates

2nd layer: Sand10cm sand, the layer consists of 2 layers of fine sand , each layer is 50mm.

Layer 3: Soil

3rd layer: SoilRed soil or which is locally available and suitable for plant growth is filled at the top layer of about 100mm depth

Testing for flow of water

Plant location

Plant : Colocasia esculenta.Location: Herohalli Raj Kaluve.

•Colocasia esculenta is a tropical plant•The selected plant Colocasia esculenta belongs to: • Kingdom - plantae • Order - Alismatales • Family - Araceae •Subfamily - Aroideae •Tribe - Colocasiodeae • Genus - Colocasia and • Species - C. esculenta .• The plant is locally known as kesaradantu in Karnataka

1

Planting to setup

Project final setup

Location of sewage sample: Mallathalli

Collection of sewage sample

•For the treatment of sewage, the grab samples were collected from Mallathalli lake located near Nagarbhavi Ring road, Bangalore.

•Collected sewage is a combination of grey water and black water.

Detention time: 7days

By providing a detention time of seven days ,the plant absorbs maximum amount of impurities present in sewage water.

RESULTS AND DISCUSSION FOLLOWING PARAMETERS WERE TESTED :-

• PH • EC• TP• TDS • TSS• SULPHATE• NITRATE• BOD • COD

Results: Sewage and Treated water

PARAMETER RESULT ( sewage

water)In Mg/l

RESULT (treated water)In Mg/l

PROTOCOL StandardLimits as

KSPCB

Phosphorus as PO4, mg/l

0.09 0.03 IS-3025 0.1

Dissolved solids, mg/l 700 885 IS-3025 part-16 2100

Total suspended solid 20 NIL IS-3025 part-17 30

BOD(5days at 20 c)⁰ 28.5 9.85 IS-3025 part-44 10

COD 220 100 IS-3025 part-58 250

Nitrate as NO3 10.5 8 IS-3025 part-34 45

Sulphates as SO4 160 238 IS-3025 part-24 1000

RESULTS: SOILPARAMETER LIMITS RESULTS before

treatment in %RESULTS

after treatment in %

pH 6 - 8.5 7.85 7.15

Electrical Conductivity ........ 0.35 MicroOhms/cm 0.28

Organic Carbon (Nitrogen) >0.51 – 0.75% 0.6 (MEDIUM) 0.88

Available phosphorous as P >10 – 25 kg/acre 12 (MEDIUM) 16

Available potassium as K >60 – 120kg/acre 85 (MEDIUM) 110Zinc >0.65ppm 0.66(SUFFICIENT) 0.7

Iron >4.5ppm 3.8 (SUFFICIENT) 4.3

Copper >0.21ppm 0.8(SUFFICIENT) 0.83

Manganese >2ppm 1.0 (SUFFICIENT) 1.5

Sulphate 28 30 20

Removal Efficiency

Parameter Removal Efficiency (%)Phosphorus as PO4, mg/l 66.66

Total Dissolved solids, mg/l …..

Total suspended solid 83.35

BOD(5days at 20 c)⁰ 71.23

COD 61.36

Nitrate as NO3 24.7

Sulphate as SO4 …..

Conclusion

• The treatment efficiency of the Angular Horizontal Subsurface Flow Constructed Wetland unit was examined by wastewater quality parameters such as pH, EC, TSS, TDS, TS, BOD, COD, Nitrate, Phosphate and Sulphate respectively, in the inlet and outlet of wastewater .

• The results in the set of Colocasia esculenta reveal that the maximum pollution reduction efficiency was observed in 70% sewage concentration.

• Angular Horizontal Subsurface Flow Constructed wetland through phytoremediation is an effective green technology for the treatment of sewage.

• The proper selection of locally adaptive aquatic plant is more trust worthy and insured technology for better treatment of sewage in local environment.

Field implementation in Bangalore LOCATION : JAKKUR LAKE• The project works like this. Out of the 49.63-hectare span of

Jakkur Lake, 4.63 hectares have been set aside adjoining the BWSSB's existing sewage treatment plant (STP) to create a man-made wetland integrated with an algal pond.

• First, sewage is treated at the plant using the regular process.

• In the second stage, the treated water is let out into the man-made wetland where aquatic plants and algae remove contaminants. In the final stage, wind and sunlight do another round of cleaning before it's released into the lake proper.

Field implementation in Bangalore • T V Ramachandra, Coordinator, Energy and Wetlands

Research Group at IISc, gives us the scientific perspective.• "The STP cannot fully remove the nutrients (nitrogen and

phosphorous) from the sewage. Hence it has to be purified in a natural way using wetlands and the water flows into the main lake spanning over 45 hectares.“

• Sounds elegant, but does it work?• For the past eight months, a team of six scientists led by

Ramachandra, have been trying to find out exactly that. They fanned out into groups to monitor and analyse the water quality. 

JAKKUR LAKE

• "At about nine locations within the lake we used to collect water samples twice at 45-day intervals

• To put it in simple words, the team found that while the STP and the man-made wetland remove 70 percent of the contaminants in about 4-5 days, wind, sunlight, and plankton in the lake proper do the rest of the cleaning.

• The team will soon submit a report to both the state and union governments to replicate the model in other lakes as well

Click icon to add picture

THANK YOU.