Hosur WTP Rehabilitation NEERI Feb 2011

Resurrection of an abandoned 23 MLD Sewage Infested Surface Water Treatment

Plant (WTP) by Disinfection at High Lime and Neutralization by CO2 at Hosur, India

Er. Dr. S. Saktheeswaran, (Ph. D, UK), MRSPH (London)[email protected]

NEERI-Nagpur-India-February-9-2011

The Bangalore Metropolis, India

The Pennaiar River for surplus sewage of Bangalore Water and the Dam

The Pennaiar River for surplus sewage of Bangalore Water and the Dam

Statement of The Problem

• Water source to the WTP is a river water impoundment• The river water has flows only in July-September • Upstream population discharges non point untreated sewage• The benthos of impoundment bears the brunt of this pollution• In summer months of March-June, the pollution is heightenedand exceeds the self purification limit

• The result is aquatic organisms became devoid of aerobic state in the upper layers and algae started decaying and water stinking.

• The 23.5 MLD capacity WTP was not designed to handle this

• To add to the woes, the ground water availability at the site was at nearly 200 m depth and the public could not afford drawing it be deep wells on a domestic scale. It resulted in exodus.

Appearance Greenish Sodium as ‘Na’ 85 to 95

Appearance after 24 hours

Greenish Potassium as ‘K’ 7 to 10

Odour Algal Total Dissolved Solids 630 to 670

Odour after 24 hours Foul stench Iron total as ‘Fe’ 0.24 to 0.52

Turbidity, NTU 13 to 20 Manganese as ‘Mn’ Nil to trace

Total hardness as ‘CaCO3’

320 to 350Oxygen absorbed, 4 Hours

5.6 to 6.8

Calcium as ‘CaCO3’ 180 to 210 BOD 14 to 18

Magnesium as “CaCO3’ 81 to 85 COD 48 to 65

Iron total as ‘Fe’ 0.24 to 0.50 Chloride as Cl 150 to 170

Manganese as ‘Mn’ Nil to trace Sulphate as SO4 40 to 52

Alkalinity Phe / total CaCo3

0 / 380 - 450 Fecal coliform / 100 ml40000 to

80000

The Raw Water Quality in the Dam in High Summer Times

Treatment Options – Chosen Option

The options considered were

1 Heavy pre-chlorination, SMBS, lime clariflocculation-rapid sand filtration, post chlorination,

2 Copper sulphate use in the impoundment,

3 Micro strainers for algae filtration and existing treatment,

4 DAF followed by existing treatment,

5 Upstream spin klin disc filters & UF membranes,

6 High Lime followed by ammonia stripping and carbonation.

No. Technology Advantages Disadvantages Choice

1

Heavy prechlorintion, SMBS, lime clariflocculation-rapid sand filtration, post chlorination

1.Prechlorintion combined with ammonia can result in chloramines 2.Chloramines result in lower concentrations of disinfection byproducts3.Chloramines do not tend to react with organic compounds and less of taste and odor complaints

1. Chlorination of decaying organisms implies potential THM formations and carcinogens.

2. Precise control of chlorine dosages is negated in this outskirts of the city

3. Leaks of chlorine gas may affect the effort by public who are already upset

No

2

Copper sulphate use in the impoundment

1.Elimination of fresh growth of algae2.Ease of application by dosing from a boat 3.Saving at least the future impoundment

1. If Cu concentrations appear in raw water, there is no way of removal in the WTP

2. The dosing will not be precise & exceed

No.


3

Micro strainers for algae filtration and existing treatment

1.Micro strainers can eliminate algae2.The downstream treatment can be easier3.Toxicity from chemical dosages is avoided

1. Micro strainers may not deal with algal lysis

2. Decaying algal stench cannot be removed

3. Basic problem of foul odour remains

No


4

DAF followed by existing treatment

1.DAF can be effective in floating out algae2.Algal scum can be put through filter press3.Resulting cake can be composted

1. Decaying algal stench cannot be removed

2. No guarantee of complete algal removal

3. Dependence on prechlorintion continues

No


5

High lime, CO2, and rapid sand filter and post chlorination

1. High ph disinfects microbes & microbes

2. It removes colour, stench, NH4 and PO4

3. No danger of THMs due to prechlorintion

1. Sludge from high lime has to be addressed

2. Need to store and use CO2 in containers

3. Ambient levels of ammonia to be monitored

Yes


6

Spin klin filters, UF membranes, existing treatment

1.Spin klin filters & UF can eliminate algae2.Avoiding dosing of chemicals

1.Dependence on the single vendor for ever2.Basic problem of foul odour remains

Next best.


Cascade and Prechlorintion

Lime Polyelectrolyte

Clariflocculation, rapid sand filter & chlorination

Cascade – No prechlorintion

High Lime pH 11 Polyelectrolyte Clariflocculation,

NH3 air stripping

Carbonation Rapid sand filter & chlorination

Existing Treatment Process / Facility

Retrofitted Treatment Process / Facility

The water that was delivered from the WTP - foul odourous & coloured

Rejected by public

Put up with by industry

Silent testimony by nearby Banyon

The Supplied Vs the Desirable The Supplied Vs the Desirable

What was Really Needed

•Learn from USA and Namibia and Singapore •Excess Lime and recarbonation•A pity this was not used for 2 years

Reasons for Abandoning Public Water Supply for 2 years

•Algal stench in treated water•Foul odour upon storage•Knowledge of sewage pollution•The tolerance - basic strength of India

The unused Gantry

Proposed to installa slotted SS tray deck over the tank sidewalls for direct placement of Lime bags

Inlet water line will be elevated to rain the water on pierced Lime bags to drain Lime solution into tanks below

Old agony and present ecstasy

Absence of algal stenchPresence of fresh odourAbsence of algal colourPresence of clarityAbsence of foulness on storageAbsence of colour in boiled riceAbsence of itching on bathingLathering on cloth washing is enhancedAesthetic willingness to drink Silent testimony by nearby Banyon

Parameters

Test Results for sample codes as underDrinking Water Standards of .Raw water

After high lime, NH3 stripping & carbonation

After rapid sand filtration & chlorination

Appearance Greenish Clear and colourless unobjectionable

Odour Algal Pleasant unobjectionable

Turbidity, NTU 13 2 1 1 - 10

Total Dissolved Solids 730 920 950 500 - 2000

pH 7.30 7.31 7.23 6.5 to 9.2

Alkalinity phe. as ‘CaCO3’ 0 0 0 No mention

Alkalinity total as ‘CaCO3’ 400 680 630 200 - 600

Total hardness as ‘CaCO3’ 290 540 515 200 – 600

Calcium as ‘Ca’ 80 210 200 75 - 200

Magnesium as ‘Mg’ 20 4 3 30 - 150

Ammonia as ‘NH3’ 14.96 4.5 nil No mention

Phosphate as ‘PO4’ 5.2 0.07 nil No mention

Oxygen absorbed, 4 Hours 5.6 0.6 0.2 No mention

BOD 7 nil nil No mention

TOC 50.99 14.50 1.50 No mention

Fecal coliform / 100 ml 50,000 2,000 Nil Nil

Sequential Water Quality During Treatment

No Parameters Prechlorintion High Lime - Carbonation

1 Colour Reverses on storage beyond 6 hours Does not reverse even after a week

2 Odour Repulsive decaying odour persists Decaying odour is completely gone

3 Keeping quality Worsens on storage of even a day No deterioration even after a week

4 Fecal coliform 50 mg/l as Cl for elimination 200 mg/l as CaO for elimination

5 TDS No appreciable increase Increases by about 200 mg/l

6 Phosphate No change Is eliminated

7 Magnesium No change Is almost eliminated

8 Calcium No change Increase by about 130 mg/l

9 Handling Hazardous Relatively safer

10 Rejects No solid wastes Sludge with high pH

11 Ambience Disturbing due to chlorine escapes Pleasant and fresh

12 Byproducts Possibility of THM and carcinogens No risk of THM and carcinogen

13 Heavy metals Cannot be removed Can be precipitates as their oxides

Relative Merits / Demerits of Chlorination Vs High Lime Neutralization

Applicability to the Disinfection Aspect of Raw Waters

The fact that raw surface waters are increasingly getting polluted by non point faecal sources as raw sewage, open defecation and disposal of rotting vegetables etc into river courses cannot be denied. It is necessary to refer to the status of pathogens in some major river waters in India

Introspection

Whereas we all accept that raw water sources should be first disinfected to become free of pathogenic coli forms, is it going to be all right to dump chlorine gas at high concentrations as 50 to 100 mg/l in raw waters and compound the issues of chlorine-decaying organics interactions with potentials of formation of THMs and carcinogens ? There is so much being written and debated on disinfection by products especially on chlorination and do we add over 50 mg/l of chlorine gas without ant concerns? Whereas we all agree that sanitation systems need to be enhanced to prevent the ingress of pathogenic & faecal organisms, is it easy to achieve it in such a vast country as India? What are we going to do by continuing to build conventional WTPs of mere prechlorintion, lime clarification, rapid sand filters and post chlorination?

Conclusion

It is high time to recognize that technologies like the high Lime-

carbonation have a significant role to play in our national

programme particularly in surface water sourced WTPs and it is

high time these are standardized by institutions as NEERI and

pollution control Boards under a central grant funding from the

GOI. It is already late considering that tenders for Agra city

WTP was invited with river Yamuna as source with lot of

fanfare but has been quietly hibernating for long.

Documents

Hosur WTP Rehabilitation NEERI Feb 2011