Effluent Treatment Plant For Dairy, Distillery and Sugar Factory

CONCEPT OF TOTAL WATER MANAGEMENT FOR SUGAR FACTORY

While Advising Environmental Management Projects of Sugar and Allied Industries, it is our observance, that an effective balance between Resource Conservation and treatment efficiencies can be grouped under a ‘Concept Working’ of ‘TOTAL WATER MANAGEMENT’.This approach is best planned from ‘Whole to Part’ theme and therefore a comprehensive work out for all the industrial sub-units in the complex, both as individual and as a part of Total Industrial Complex is beneficial, as there is considerable linking in the process applications. The following work areas are therefore envisaged in our concept of ‘Total Water Management’.

TOTAL WATER MANAGEMENT OF SUGAR FACTORY COMPLEX

TREATMENT THEME

Considering the basic philosophy that ‘Waste is a misplaced resource’, a strategy is devised, wherein it is possible to segregate the various wastewater streams and in the first place, try to reuse them as it has for suitable application in processes. If a stream cannot be directly used, applying the ‘Selective treatment’ methodology to have optimum treatment of the same, of course at minimum energy and other resource pending.
This is summarized in the approach leading to:

Reuse of waste, leading to Resource conservation.
Minimization of Energy consumption.
Reduction in Environmental Liability.
Cost effective treatment approach for effective and efficient performance.
Advanced yet simple approach.

The treatment theme therefore is devised on three main planks:

In Plant Control Methods
Pre-Treatments
Treatment Chain - Comprising of
- Secondary Treatment
- Tertiary Treatment

IN PLANT CONTROLS AND PRE-TREATMENT

TREATMENT APPROACH

The sugar factory effluent emanates mainly from washing, cleaning operation thereby entraining organic load and suspended solids load in the form of sugar juice, sugar particles, bagasse etc. in the wash waters leading to effluent generation. The first step that will be taken for prevention of unnecessary hydraulic and organic loading shall be in plant control by minimizing water use and thereby effluent generation, effecting partial recycle of streams like condensates and cooling waters. Segregation and selective treatment of effluent sub-streams shall also be implemented. For example, the streams, which do not contain organic matter, like Boiler Blow-down, shall be segregated, subjected to separate treatments like cooling, settling, filtration, and the water shall be reutilized for Non-Process applications like ash quenching etc.
The Mill House Effluent containing suspension and free oil shall be segregated and subjected to a ‘Primary Treatment’ unit comprising of mechanized screen and mechanized Oil and Grease skimmer. After this, the boiling house effluent shall be joined in to this stream and the combined effluent shall be subjected to Further Treatment.

SCHEMATIC PROCESS FLOW DIAGRAM FOR INPLANT CONTROL SYSTEM FOR SUGAR FACTORY

INPLANT CONTROL SYSTEM FOR SUGAR FACTORY

SEGREGATION AND SELECTIVE TREATMENT – FOR MILL HOUSE EFFLUENT

Mechanized Screen

Auto bagasse removal screen in Mill section helps to remove bagasse from mill house effluent, thereby reducing suspended and organic matter pollution load to Effluent Treatment Plant

Mechanized Oil Skimmer

Presence of oil and grease in the effluent can severely affect the biological mode of treatment. A Mechanized Oil and Grease Removal Mechanism is therefore proposed to separate out the oil and grease content of the effluent before subjection to the biological treatment mode.

Dual Media Filter

To remove trace suspension and organics, a polishing unit of Dual Media Filter consisting of filtration media sand and anthracite charcoal.

VOLUME AND CONCENTRATION REDUCTION

Arrangement for segregation and reutilization of effluent having probability of accidental entrainment of juice or syrup shall be made. Provision of this has proven to result in reduced organic matter concentration in the effluent to be treated.

Observing the characteristics, it is evident that the combined effluent is biodegradable. It is also observed that a Primary anaerobic Phase Biological Treatment imparts two advantages, one, since the phase does not involve mechanical aeration, it reduces organic matter concentration by more than 50% efficiency, without energy input, thereby making the total Energy requirement by more than 50% of Conventional treatment. But, the most important advantage observed in case of Sugar factory effluent is the capacity to absorb shock loading is far better, as compared with that for Aerobic mode. The effluent shall therefore be subjected to Anaerobic phase.
The most effective Aerobic Treatment mode determined for the sugar factory effluent is ‘Extended Aeration’ where the F/M is kept low and MLSS concentration high by optimum sludge recirculation, Two-stage Aeration-Clarification Process is suggested followed by Tertiary Treatment.

Tertiary Treatment

The treated effluent after this treatment shall achieve the stipulated norms for disposal on land for irrigation. In order to further safeguard against minor variations, a tertiary treatment comprising of Multimedia Filter for reducing turbidity and Activated Carbon Filter for reducing trace colour and organic matter is proposed. This will render the treated effluent fit for reuse for non-process applications.
Excess Sludge Drying
For Drying of the excess sludge, in place of the present Sludge Drying Beds, which results in odour nuisance and which is a Manpower intensive process, Filter Press is recommended, which shall result in Drip-free sludge.

Treatment Chain

SCHEMATIC PROCESS FLOW DIAGRAM FOR EFFLUENT TREATMENT PLANT FOR SUGAR FACTORY

COOLING TOWER OR SPRAY POND OVERFLOW TREATMENT FOR SUGAR FACTORY

The overflow from Spraypond or cooling tower in the sugar factory necessarily contains sulphates concentration and trace organics. Mixing of this effluent stream in the ETP for sugar factory, which normally contains first stage anaerobic digestion process and which results in pH destabilization and causes further problems in treatment, since the high sulphate concentration is detrimental to methane formers due to formation of H2S, this affects the biogas quality also.
In order to limit the H2S concentration for the above reason, it is proposed to have a Sulphate conversion to CaSO4, by utilizing the pre-treatment of Reaction Tank, flocculation and Lamella clarifier, and by providing suitable sludge drying mechanism like filter press. The effluent, with reduced sulphate concentration shall be fit for further Anaerobic Digestion Process, which has the advantages like reduced sludge generation, far lower energy consumption, besides better stability against variable loadings.
If organic contents are well within limits, this stream can be directly joined to later stage treatment, even at treated sump.

Technical Note