MANAGEMENT OF WATER IN DAIRY PLANTS
content:
- Introduction
- Water Uses and Sources
- Areas of Water Loss
- Water Use Economization
- Water Reuse
- Epilogue
- News Section
1. INTRODUCTION
- Dairy Farmers in Lidcombe (Australia) joined the Sydney Water
‘Every Drop Counts’ water minimization business partnership. The company installed 27 water meters across the site and worked on developing an accurate understanding of water flow to each area. A water assessment was undertaken over a number of months, identifying savings by preventing cooling tower overflow; re-circulating homogenizer water, crate wash water; reducing water for cleaning; repairing leaks; and reviewing truck washing practices. The assessment identified total savings in water costs of US $ 3 lakh (Rs. 1.5 crore approx.) per year with an initial cost of US $ 1.5 lakh (Rs. 75 lakh approx.) and ongoing cost of US $ 26,000 (Rs. 13 lakh approx.) per year (1).
- A dairy in UK, processing around 25 lakh litres per day, recovers all condensate from its evaporators, which is then treated by reverse osmosis and disinfected to provide cleaning water. The amount of water evaporated is in the order of 20 lakh litres per day. Approximately 10% of incoming flow is rejected and sent to effluent treatment. This means that the requirement of fresh water is reduced by a whopping 18 lakh litres per day. The company aims to have zero potable water input to the site(2).
- Hard cheese manufacturer TNUVA (Israel) used to drain all spent caustic solutions – average volumes of 2 tonnes of 48% caustic and
50,000 litres of hot water per day. The company installed a nanofiltration regeneration unit to continuously regenerate caustic CIP solution thereby only draining the retente of the membrane filtration. The consumption of chemicals for the caustic CIP system was reduced to 50 kg of 48% NaOH and 1250 litres of hot water per day. The annual net savings were in the order of US $ 1 lakh (Rs. 50 lakh approx.) with a simple pay-back time of less than two years(2).
These are a few examples of water management practices employed in some dairy plants which amply demonstrate the benefits of water management (conservation) in dairy processing.
1
We all know that water is an important utility for dairy plants as it governs the hygiene of plants. In the past, abundant and inexpensive sources of water were taken for granted in the dairy processing industry and not much thought was given to economize its use. But, in recent times we have witnessed acute water scarcity and drought conditions in various parts of particularly Karnataka, Tamil Nadu, Andhra Pradesh, Maharashtra, Gujarat and Rajasthan. With the available water sources becoming scarce, many dairy plants, located in such areas, find it difficult to operate or otherwise expand their operations. Besides, indiscriminate use of water also results in excessive wastewater generation, which becomes a burden for the dairy in terms of treatment and disposal costs.
Dairy processors, therefore, are aggressively challenged to conserve water necessitating the need for not only reducing water consumption but also to employ measures for recovery and recycling of process water without compromising on the hygienic quality and safety of the products.
2. WATER USES AND SOURCES
2.1 Water usage areas: Water used in a dairy processing establishment could be broadly classified into the following major categories:
i. Process water: Water used for direct preparation of products, cleaning purposes and various technical purposes. Examples are: washing / cleaning of equipment, transport of product, dissolution of ingredients, water remaining in the final product etc. A characteristic of process water is that it comes into contact with product directly or indirectly. Therefore, process water should meet drinking water quality.
ii. Cooling water: Cooling water is the water used for removal of heat from process streams and products. The quality requirements for cooling water used in plate heat exchangers to cool milk is critical,
2
since with this type of equipment there is a risk of failure and leakage of cooling water to product. In such situations cooling water should be of drinking water quality.
iii. Boiler feed water: Boiler fed water is required for steam production.
The main quality requirements are low hardness and low air and carbon dioxide content.
iv. Miscellaneous: Other uses of water in a dairy plant are for ancillary purposes such as amenities and gardens, and extraordinary incidents (e.g. fire protection).
Depending upon product mix, dairy processing plants can use substantial volumes of water for cleaning, cooling towers, boilers and other processes. Figure 1 shows typical water use in dairy processing plant producing market milk(1).
A study(1) of some dairy plants in Australia revealed water-to-milk intake ratio (litre / litre) for different products as under:
|
Products |
|||
|
Milk and flavoured milk (excluding UHT milk) |
1.05 |
2.21 |
1.44 |
|
Powdered products |
0.07 |
2.70 |
1.52 |
|
Cheese and whey products |
0.64 |
2.90 |
1.64 |
As is seen from the results of the study, water consumption in some plants is less than a litre per litre of milk processed.
2.2 Sources of water: Water supply to dairy processing plants varies according to location, but may be from town water, bore wells, wells, river, dams or irrigation channels.
3. AREAS OF WATER LOSS
Some common reasons for excessive water usage and loss are as listed below:
|
RMRD:
|
|
Process Section:
|
|
Milk Filling Section:
|
|
Butter and Ghee Section:
|
|
Evaporating and Drying Sections:
|
|
CIP Systems:
|
Refrigeration Sections:
- Draining of chilled water or leakages in chilled water system
- Evaporation losses in atmospheric condensers
Other general areas:
- Inadvertent use of water at wash points
- Frequent and excessive floor cleaning by high pressure discharge points
- Draining of pump seal water
4. WATER USE ECONOMIZATION
Significant drivers for water conservation are:
- Increasing water costs
- High water consumption is making availability critical in some cases
- Future regulations may require water conservation
- Increased costs for treatment and disposal for excessive wastewater generated due to indiscriminate use of water
Thus, there are gains to be made by the dairy processors in minimizing water consumption within factories. A study (3) on water management in a couple of dairy plants in Gujarat, suggesting potential areas for water conservation and potential cost benefits, indicated the following:
|
|
Average milk handling per day (Ltrs.) |
Likely water savings per day (Ltrs.) |
Potential monetary savings per year* (Rs.) |
|
Dairy Plant I: Lean Flush |
5,15,000 9,20,000 |
5,92,705 8,24,130 |
11,88,469 |
|
Dairy Plant II: Lean Flush |
45,000 1,15,000 |
1,02,880 1,29,842 |
49,762 |
|
* Estimated on the basis of savings in power (operation of raw water bore well pumps, soft water pumps), salt (regeneration of softner) and fuel (heating of fresh water). |
|||
In dairy production, there are various possibilities for increasing water use efficiency and promoting water reuse. Dairies’ water conservation agenda could be based on some of the following important pillars(4):
- Think of water as a raw material with a cost.
- Make water conservation a management priority.
- Set specific water conservation goals for your plant.
- Reuse water where possible.
- Train employees how to use water efficiently.
- Establish a recognition and reward program for employees and teams who do an outstanding job.
A UNEP publication(5) reports that due to higher costs of water and effluent disposal that have now been imposed in some countries to reflect environmental costs, considerable reduction in water consumption has been achieved over the past few decades in the dairy processing industry. For example, in medium consumption category, the consumption has been decreased from 3.25 litres water / litre of milk in 1973 to 1.3-2.5 in
1990.
Strategies for reducing water consumption involve examining cleaning procedures, operator practices and also involving technological solutions for equipment upgrade. By doing so, water consumption can be reduced to as little as around 1 litre of water per litre of milk intake.
4.1 Water wastage control(1, 6): To implement an effective water control programme, it is essential that adequate water metering facilities are installed at the dairy plant. This should include a meter at each of the points of entry of water into the dairy plant, and meters on the supply to individual departments or equipment with major usage of water. Money invested in such meters is useful.
Some specific opportunities for dairy industry to decrease water use, primarily by controlling losses, are shown below:
Manual cleaning:
- Review cleaning practices, adopt dry cleaning, where possible
- Use high pressure low volume cleaners for cleaning surfaces
- Use automatic shut-off nozzles on all water hoses.
- Pre-soak floors and equipment to loosen dirt before final clean
|
|
CIP systems:
|
|
Processing:
|
|
Auxiliary use:
|
|
Cooling towers:
|
|
Miscellaneous:
|
The above details are not exhaustive, but provide a brief insight of common focal points.
- WATER REUSE
Besides preventing loss of water, optimization of water use in a dairy plant could also be effected by water reuse, as appropriate, for specific applications. This can reduce the demand on water supply and also reduce volumes of wastewater, the treatment and disposal of which is expensive.
A proposed draft document(7) on guidelines for hygienic reuse of processing water in food plants is under consideration of the Codex
Committee on Food Hygiene (CCFH). The next two sections (5.1 and
5.2) are based on the information provided in this partially developed document.
5.1 Reuse water: Water that is considered suitable for reuse is the one that has been recovered from a processing step, including from the food components, and that after subsequent reconditioning treatment(s), as necessary, is intended to be re(used) in the same, prior, or subsequent food processing operation. Reuse water includes:
- Recirculated water: Water reused in a closed loop for the same processing operation (e.g. chilled water, condenser cooling water in circulation, pasteurizer cooling water in circulation etc.)
- Reclaimed water: Water that was originally a constituent of food, has been removed from the food by a process step, and is intended to be
subsequently reused in food processing operation (e.g. condensates
from milk evaporators).
- Recycled water: Water, other than the first use or reclaimed water, that has been obtained from a food processing operation (e.g. permeate from reverse osmosis plant, CIP final rinse water etc.)
5.2 Requirements for hygienic reuse of process water: Some important requirements for hygienic reuse of processing water in dairy plants are:
- Reuse water shall be safe for its intended use and shall not jeopardise the safety of the product through the introduction of chemical, microbiological or physical contaminants in amounts that represent a health risk to consumer.
- Reuse water should be introduced into a processing system such that it will not add to microbiological or chemical burden of the product. Such water shall at least meet the microbiological and, as deemed necessary, chemical specifications for potable water. In certain cases physical specifications may be appropriate.
- Reuse water should not adversely affect the quality and suitability of the product.
- Reuse water shall be subjected to ongoing monitoring and testing to ensure safety and quality. The frequency of monitoring and testing are dictated by the source of water or its prior condition and the intended reuse of water; more critical applications normally require greater levels of reconditioning than less critical uses.
- Unless reconditioned to potable water quality, distribution of reuse
water should be in clearly marked (e.g. different colours) systems, including piping and outlets, that are separate from the distribution lines for potable water. Cross-contamination by backflow, back- siphonage, or cross connections from reuse water should be prevented.
- Reuse water storage vessels, if used, should be properly constructed of material(s) that will not contaminate the water and should allow for periodic cleaning and sanitizing where appropriate.
- Proper maintenance of water reconditioning system is critical to avoid having the systems become source of contamination. For example, filter systems can become sources of bacteria and their metabolites if bacteria are allowed to grow on entrained organic materials removed from the incoming water; proper maintenance and testing is needed to ensure absence of this situation.
5.3 Treatments of reuse-water: To achieve sustainable water management in a dairy factory, both the quantity and quality of water need to be considered. Generally speaking, two scenarios can be distinguished for water reuse:
- Water not in contact with raw, intermediate or final product: Typical reuse applications are for cooling purposes and for generation of
‘non-food steam’.
- Water in contact with the products (e.g. water used for cleaning of equipment, reconstitution, washing of products such as butter, cheese and paneer, moisture adjustment in products such as butter, etc.).
In some case water can be reused without pre-treatment (e.g. the use of condensates as washing water). However, in most cases, water that is recycled or reused will need to be treated to improve its quality particularly when it comes into contact with food or is used to clean surfaces that will come in contact with the products.
Advanced water treatment technologies make it possible to treat water to very high degree, significantly reducing potential health risks associated with water reuse. It is even possible to treat wastewater to such a high degree that it can be safely used as a supplement to potable drinking water supplies(8). However, treating water to a high degree is expensive. The quality of water, and the degree of treatment required, should correspond to the intended water use.
The table below provides a broad idea about the possible reuse of water and appropriate treatment requirements:
|
Water quality requirements in a dairy(2) |
||||
|
Water → Source |
Used CIP cleaning solution |
CIP final rinse |
Condensate |
Permeat e from RO plant |
|
Application ↓ |
||||
|
Vehicle washing |
1 |
1 |
1 |
1 |
|
Crate washing |
2 |
1 |
1 |
1 |
|
Manual cleaning of equipment |
3 |
3 |
2 |
1 |
|
CIP pre-rinse |
1 |
1 |
1 |
1 |
|
CIP- main wash supply |
2 |
3 |
2/3 |
1 |
|
CIP final rinse |
3 |
3 |
3 |
1 |
|
Water purge of product lines |
3 |
3 |
3 |
1 |
|
1: Direct reuse 2: Reuse after screening of solids 3: Reuse after suitable membrane separation |
||||
While deciding on the type of water treatment system for use, it is important to consider the following points:
- Reconditioning of water should be undertaken with the knowledge of the types of contaminants the water may have acquired from its previous use. E.g. UV disinfection may have limited effectiveness for inactivating protozoan cysts, helminths or viruses. Similarly, the use of chlorine or ozone on organically enriched water may result in the formation of hazardous organic compounds.
- The water treatment system(s) chosen should be such that it will provide the level of reconditioning appropriate for the intended water reuse. E.g. UV disinfection as the sole treatment is not appropriate for water that is turbid or contains particulates because the organisms in the shadow of particles or entrained within particles are protected from lethal effects of the irradiation.
- Extremely large volumes of reuse water may justify the use of an advanced wastewater treatment system. Such systems, depending upon the prior state of the water, may require the use of one or more processes such as filtration, de-nitrification, phosphorus removal, coagulation-sedimentation, and disinfection.
Overall, matching water quality requirements with the type of water use requires analysis of the critical control points and an evaluation of the potential for contamination of food products. Therefore, in addition to developing a framework for water reuse in food production / processing, where possible water reuse in the factory should be integrated into existing HACCP programme.
5.4 Some possible uses of condensate and reverse osmosis permeate(9): Possible uses for recovered vapour condensate or reverse osmosis permeate could be divided into 3 broad classes.
- Vapour condensate as a heat source:
- As boiler feed water
- For melting butter in a jacketed tanks
- For preheating (through heat exchanger) milk prior to entering evaporator
- For preheating (through heat exchanger) drying air for spray dryers.
ii.Vapour condensate and reverse osmosis permeate for product washing and product uses:
- As a cheese curd wash water
- As casein wash water
- Water for reconstitution of powdered products.
- Recirculation water for evaporator on failure of product feed
- Diafiltration water in ultrafiltration installations
However, utilization of vapour condensate and RO permeate for product uses needs strict collection and treatment practices for food safety and economic reasons. In particular, their bacteriological, chemical and organoleptic characteristics require close monitoring.
iii.Vapour condensate and reverse osmosis permeate as water and heat source:
- For CIP, pre and intermediate rinsing instead of potable water use
- For preparation of CIP solutions
- For cleaning of floors and walls of the building
- For external cleaning of milk transport vehicles
- For use after cooling, as pump seal water.
6. EPILOGUE
Shortage of water is currently the most urgent environmental problem facing countries, and dairy industry is not insulated either. Sources of water supply are inadequate and have a limited capacity for replenishment. To achieve sustainable water management, industry needs to focus on low cost solutions for reduction in water consumption i.e. employing efficient practices. Subsequently, the scope can expand, bringing around infrastructural improvements such as equipment upgrades, efficient water treatment systems etc.
REFERENCES
1. Prasad, P. and Pagan, B. (2004), Eco-efficiency and dairy processing, The
Australian Journal of Dairy Technology (Vol. 61, No. 3 – October 2006), pp
231-237
2. Andersen M. and Kristensen G.M. (2004), A generic approach to water minimization and reuse in industry – implications in dairy operations, The Australian Journal of Dairy Technology (Vol. 59, No. 2 – August 2004), pp 73-
3. Sharma, K. and Saxena, R. (1991), Water Management in Dairy Plants (Project
Report), Institute of Rural Management, Anand.
4. Rausch, K.D. and Powell G.M. (1997), Dairy Processing Methods to Reduce Water Use and Liquid Waste Load, Cooperative Extension Service, Kansas State University.
5. COWI Consulting Engineers and Planners(2000), Cleaner Production Assessment in Dairy Processing, United Nations Environmental Programme, Division of Technology, Industry and Economics.
6. Hale, N. et al (2003), Sources of Wastage in Dairy Plants, Bulletin of the
International Dairy Federation No382/2003, IDF, Brussels, pp 7-30
7. Proposed Draft Guidelines for the Hygienic Reuse of Processing Water in Food Plants(CX/FH 01/9 (2001), 34th Session of Codex Committee on Food Hygiene (Bangkok, 2001)
8. Kirby, R.M. (2004), Water – A food processor’s point of view, The Australian
Journal of Dairy Technology (Vol. 59, No. 2 – August 2004), pp 100-106
9. IDF(1988), The Quality, Treatment and Use of Condensate and Reverse Osmosis Permeates, Bulletin of the International Dairy Federation No232/1988, IDF, Brussels
NEWS SECTION Indian Food laws
- Notification GSR 773 (E) of 29 December of the Ministry of Health and Family Welfare: The notification amends Sub-Rule (2) of Rule
57-A pertaining to ‘Crop Contaminants’ by specifying a maximum
limit of aflatoxin M1 in milk as 0.5 µg/kg. The amendment, which is in harmony with the Codex standards, will become applicable from 30
March 2007.
Codex Alimentarius Commission
- The period April - June 2007 features meetings of the following
Codex subsidiary bodies:
- Codex Committee on General Principles (CCGP), 02-06 April, Paris, France
- Codex Committee on Contaminants in Foods (CCCF), 16-20 April, Beijing, China
- Codex Committee on Food Additives (CCFA), 24-28 April, Beijing, China
- Codex Committee on Food Labelling (CCFL), 30 April – 04 May, Ottawa, Canada
- Codex Committee on Pesticide Residues (CCPR), 07-12 May, Beijing, China
International Dairy Federation (IDF)
IDF World Dairy Summit 2007 is being organized during 29 September –
4 October 2007 in Dublin, Ireland. The event features IDF business meetings on 29 and 30 September, an IDF Open Session on 1 October, and technical sessions (3 parallel symposia daily) during 2-4 October
- Some of the areas covered in the symposia include:
- Dairy policy and economics
- Development in dairy science and technology
- Environment
- Nutrition and Health
- Marketing including nutrimarketing
- Milk production and farm management
- Functional foods
Whereas, business meetings are open to invitees only, the IDF Open Session and technical symposia are open to all the delegates who register for the event. Details are provided on the website: www.wds2007.com.
14
Technews Issue No.66 (January-February 2007
|
MANAGEMENT OF WATER IN DAIRY PLANTS |
|
I find this bulletin:
Useful Informative
Only entertaining Boring
I think the format of this bulletin needs/does not need change. I would like information in any subsequent issue on |
|
Please send your letters to:
National Dairy Development Board Post Box No.40 Anand 388001 Gujarat
Fax No. (02692) 260157 Email : nnv@nddb.coop |
|
|
