Common Effluent Treatment Plants

Common Effluent Treatment Plants


INTRODUCTION
Urbanisation and need for better living has incessantly generated requirement of consumer goods and infrastructural inputs. With market potential and easy finance available, the mushrooming rise in the number of small scale industries can be seen in any Indian city. Besides being a resource for market economy and production of large number of consumer items, it is generally observed that, either due to their economies of scale coupled with their unplanned growth and dearth of affordable and cost- effective treatment technology, efforts by small scale units in achieving the environmental compliance have not been effective. Their large number and diverse trade has further aggravated the problem. Under these constraints, setting-up of individual full-fledged treatment device is no longer feasible. Hence the desirable option is of the shared or combined treatment, wherein, managerial and operational aspects are collectively addressed and the cost of treatment , becomes affordable as enunciated in the scheme of the common effluent treatment plants, which are proving to be a boon especially for small entrepreneurs, given the methodical planning, regular operation and equitable contribution of member units. Such common facilities also facilitate proper management of effluent and compliance of the effluent quality standards.

CONCEPT OF COMMON TREATMENT
• The concept of effluent treatment, by means, of a collective effort, has assumed reasonable gravity by being especially purposeful for cluster of small scale industrial units. Common effluent treatment plant (CETP) not only help the industries in easier control of pollution, but also act as a step towards cleaner environment and service to the society at large. Small scale industries, by their very nature of job cannot benefit much from economies of scale and therefore the burden of installing pollution- control equipment, falls heavy on them. Realising this practical problem, under the policy statement for abatement of pollution the Govt. felt to extend the scheme for promoting combined facilities for treatment of effluent and management of solid waste for clusters of small scale industria l units and also to provide technical support to them. Accordingly, Ministry of Environment & Forests, Govt. of India, had instructed various State Pollution Control Boards, to examine the possibilities of establishing CETPs in various Industrial estates in the respective states.
The concerted approach of joint or common effluent treatment provisions has many advantages. Wastewater of individual industries often contain significant concentration of pollutants; and to reduce them by individual treatment upto the desired concentration, become techno-economically difficult The combined treatment provides a better and economical option because of the equalization and neutralization taking place in the CETP.
Other important issues for the merit of common treatment include, scarcity of land at the industry's level and a comparatively easier availability of professional and trained staff for the operation of CETP, which can otherwise be difficult, at the individual industry level. For the regulatory authorities also, common treatment facility offers a comparatively easier means of ensuring compliance of stipulated norms. The handling and disposal of solid- waste also becomes increasingly easier as the infrastructure is created in the project itself. The concept of common treatment, based on feasibility, should be part of the new industrial estates as essential component of infrastructure, In fact, the location of industries should always be such that units with compatible nature of activity are located in a cluster which in-turn can facilitate in providing common treatment .

Measures for optimum efficiency
Operation of CETP being a participatory mechanism, the primary requirement is hence to define the ultimate responsibility for the proper functioning of the plant after it is commissioned. The important issues which merit consideration are :
Aspect of Ownership
Various ownership alternatives include- the plant owned by government, consortium of industries or by an independent body. Whatever be the case, the primary emphasis should be on responsiveness in terms of effective and optimal operation of the plant and accountability. The member industries should also be made to realise that they are equally responsible for the sustenance of the plant.
Conveyance System

Different from the discharge characteristics of an integrated ( big) industrial unit, small scale units usually generate higher proportion of floating or suspended particles in their effluent streams. At times their job operation result in high corrosive effluent. In either of these cases , to effectively convey their effluent to the CETP , it becomes necessary for individual units to set-up a ‘pre - treatment’ device. It is also necessary that the conveyance network be so designed as to ensure their periodic de-sludging. Care should also be taken to minimise on cost of operation by facilitating conveyance through gravity flow, instead of multistage pumping. In fact the location of CETP should be selected after a careful topographical survey of the drainage area to keep the conveyance route as short as possible. The chances of flooding in monsoon and accidental surface run-off into the conveyance route should also be looked into. Conveyance by tankers is another option, provided the chances of leakage are effectively checked and their transit is strictly monitored in accordance to a properly laid down system.
Cost of Treatment

The cost effective treatment supported with a system of regular collection / payment of treatment charges by each member unit, while maintaining its effluent quality within acceptable norms are some of the prerequisites. The system of payment should be legally supported to provide a check for non-payment of dues and to take steps against defaulters.

Criteria for Cost
The cost sharing should be decided in such a way that volume of effluent becomes an important norm, but its share in the total cost should not be such as to encourage by-passing of dilute streams and conveying highly toxic / non-biodegradable waste to CETP. The treatability factor should also be given due consideration in cost estimation. An effort by the industry to segregate toxic, highly acidic / highly basic, or toxic metal bearing waste be made to explore the possibility to de-toxify / neutralize or to attempt the recovery of metals by installing recovery plants, which are feasible and economically viable on account of their pay-back potentials.

Plant Design
The approach to provide treatment at low cost, an important factor in common treatment, depends on appropriate design of CETP. In keeping with the diverse nature and scale of operations, typical of small scale units, low capital investment and lower operation and maintenance cost incurred on treatment is a prime factor. In such a situation mechanical and chemical processes are advantageous over bio-logical systems. And the least preferred are conventional anaerobic processes on account of huge space requirements and least flexibility. Though,, the advanced UASB technique with less hydraulic retention and space requirement being significantly low, anaerobic system is also a possible option. In order to obviate the need of excessive civil work at CETP in making huge equalization and settling units, the member units should also provide settling and neutralization of their individual waste.

In order to minimize on the electrical cost, the possibility of substituting bio-energy should be explored to the extent possible. Proper management of sludge with its nutritive value would mobilize resources to substitute the operational cost.
While designing the plant it would be of additional advantage to keep manpower requirement as low as possible but high in technical skills to reduce down-time for maintenance.




Advantages of Common Treatment

o Saving in Capital and operating cost of treatment plant. Combined treatment is always cheaper than small scattered treatment units.
o Availability of land which is difficult to be ensured by all individual units in the event they go for individual treatment plants. This is particularly important in case of existing old industries which simply do not have any space.
o Contribution of nutrient and diluting potential, making the complex industrial waste more amenable to degradation.
o The neutralization and equalisation of heterogeneous waste makes its treatment techno-economically viable.
o Professional and trained staff can be made available for operation of CETP which is not possible in case of individual plants.
o Disposal of treated wastewater & sludge becomes more organised.
o Reduced burden of various regulatory authorities in ensuring pollution control requirement.