Water Conservation in a Dairy Plant

Water has diverse uses in a dairy processing plant. It is used for heating, cooling,washing and cleaning. The consumption of water in these operations generally ranges from three to four liters for processing one liter of milk. However, there are examples where plants has reduced the consumption to one liter water for processing one liter of milk. Water conservation in a dairy processing plant gives dual benefits.

It lowers the water and energy bill of the plant. It also helps to reduce the effluent treatment cost as all the water from the plant reaches the effluent treatment facility before its disposal. With growing awareness, there will be pressures on industries to conserve water. This is being thought as environment friendly and it will partly pave way to sustainable development.For successful implementation of the water conservation measures, the commitment of management is required. Once the management decides to adopt water conservation, it should try to change the mind set of all the people involved. The management should evolve strategies to train and motivate plant personnel to achieve the goals of water conservation. The people involved in it should consider the water as a raw material with a cost and the management should encourage people to innovate.

Every plant should map water usage and decide where water can be moved from one process and used in another process. In some cases, water can be reused without any treatment. In other operations, water might require treatment before it can be used some where else. All water for reuse should be screened to reduce solid buildup. Chlorination is recommended for all reused water, and the residual chlorine level should be increased to 4 mg/l twice a month to make sure that organisms that could harbor in the organic rich environments are killed.

The following water conservation tips can be applied in dairy plant:

•  Use automatic shut off devices on water hoses on steam and water mixing systems.
•  High pressure jets for cleaning cans, tankers and silos will require less water.
•  Install water meters and read them after each shift to identify people who are conserving water.
•  Wherever possible, try to reuse water where possible. For example, hot water used for rinsing after cleaning in a cleaning in place (CIP) cycle could be used for prerinsing in next CIP cycle. Use level controllers to control the pumps. This will avoid overflow from tanks.
•  Frequency of cleaning can be reduced by adopting continuous processes in place of batch processes. Especially in dairy plants producing traditional Indian dairy products, the introduction of continuous machines will lead to greater
• hygiene and less frequent cleaning.
•  Use optical sensors for automatic shut off valves in wash rooms and urinals.
•  Avoid spillage of products and raw materials. Clean the spills before washing with water. Don’t use water jets to sweep the spilled materials in to drain. This is the usual practice in many diary plants.
•  Automation of operations leads to low water consumption. Hence, automate CIP cleaning and other processing operations.

Materials of Construction of Rain Water Harvesting System

Various materials can be used for different components of a rainwater harvesting system. These are given below:

Roof: The Rainwater can be collected from the roof made of clay tiles or cement plastered surface. Metal roofing can also be used. We can paint the roof material to reduce its porosity. Avoid using lead based paint, as it will provide chance for leaching of lead into harvested rainwater. Other roofing materials such as composite asphalt, asbestos and concrete tiles which might leach chemicals that affect the quality of water harvested.Gutters and connecting pipes: Gutters are generally made up of seamless extruded aluminum. The Galvanized iron or PVC are commonly used for connecting pipes.

Leaf Screens: Leaf screens are wire mesh of suitable thickness with metal or plastic frame.

Graded filter: The structure for filter could be masonry, concrete or plastic. This structure will be filled.

Tank or Storage structure: Masonry, concrete, plastic, steel and fiberglass are the generally recommended materials for storage structure. The material should be inert and durable. Depending on the intended use, like water for gardening, we can use open ponds lined with polythene sheets. Such innovations will greatly reduce the cost.

Water Treatment System: For non potable uses, simple cartridge filters are sufficient. If the rainwater is used for drinking purposes, a tank for chlorination or a zone of UV light for disinfection of water should installed.

Distribution System: The distribution piping is generally made of galvanized iron.

How Much Water Can We Collect?

Rainwater harvesting systems generally have the following main components. These components are listed here:

•  Roof/catchment area
•  Gutters and connecting pipes
•  Leaf screens and first flush diverters and graded filter filled with coarse sand, gravel and pebbles
•  Storage Tank
•  Water Treatment system
•  Water distribution system

Though in some domestic rainwater harvesting systems you may not find the graded filter. In some large-scale rainwater harvesting systems, it may be advantageous to have a sedimentation tank before graded filter to settle the dust particles. Main components of a domestic rainwater harvesting system shown in Figure

i. The Roof / Catchment Area

Rainwater can be collected from any inert roofing, that is, it won’t leach out any chemicals into rainwater. It is important that no lead is used as roof flashing or gutter solder, as the slightly acidic quality of rain can dissolve the lead and contaminate the water supply. Be aware that some composite asphalt, asbestos, concrete tiles and lead based paints can leach pollutants and affect the quality, colour and taste.Therefore we need to pay special attention to roofing, if we are going for rainwater harvesting. We may paint the roof with non-toxic paints to make the roof less porous and increase the collection efficiency.

Rainwater Harvesting System

ii. Gutters and Pipes

These are the conduits from the collection surface to storage tank. Size and slope of these will affect collection efficiency of the rainwater harvesting system. We need bigger size to avoid spillage and overflow during most intensive rainfall anticipated. But increasing size will increase the cost of installation, which is will give added advantage only during heavy rains. So we need to optimize the size.During off-season, rodents might make these pipes as their homes. So check gutters and pipes periodically for rodent infestation.

iii. Leaf Screens, First Flush Diverters And Graded Filters

The function of leaf screens is to prevent leaves and other debris from entering the rainwater collection system. Primary leaf screening devices may have a 6mm wire mesh in a metal or plastic frame installed on the top of gutter. The rainwater entering gutter will pass through the screen and leaves and rags etc. will be retained by the screens. If there are trees nearby and leaves pose a problem, a leaf screen may be installed along the entire length of the gutter.The first part of the rainfall picks up most of the dirt, bird droppings and debris.This initial rainwater needs to be diverted. First flush diverters are the devices used for removal of this dirt and debris (shown in the Figure 20.2). The first flush diversion devices are nothing but a short pipe/ small chamber near the entrance of gutter where rainwater from roof is collected. As the rain fall starts, the initial water carrying dust and debris will fill this pipe or chamber. After that the rest of rain water find its way to graded filter and storage tank. The small chamber/pipe has a valve in the base that allows it to empty before the next rainfall. Typically 40 liters of water for every 100 square meters of roof area is diverted.Graded filters are structures used for removal fine suspended particles. These are filled with coarse sand, gravel and pebbles sequentially to make a filter bed. The size of particles in each layer and depth of layer will influence the in efficiency of particle removal and head loss or pressure difference across the bed. Higher efficiencies can be achieved by use of small size of particles with increased depth. But this will lead to more head loss in the bed. These filters are prone to clogging. So you need to clean it or have provision for backwashing. In backwashing, pressurized water enters from bottom and leaves through top layer. This operation will remove particle adhered to pebble, gravel and sand.

iv. Storage Tanks

The characteristics of a good storage tank include durability, leak proof, opaque exterior and a clean, smooth interior. The tank should be located near a cool place where less light falls. This will inhibit the growth of algae. If tanks are not opaque and if lot of sunlight is there, the algae growth will be prevalent. We can construct the tank from many materials such as plastic, steel, concrete and fiberglass. Tank should be covered properly to prevent evaporation, mosquito breeding and to keep insects, rodents, birds, and children out of reach. Provide a manhole for tank cleaning and suitable overflow outlet for excess water removal. The elevation of tank can be above ground, below ground, or at the ground level. It could be wall mounted just under the gutter. It is best to locate the tank in a cool place, out of sunlight to inhibit the algae growth.We need sufficient storage capacity of the tank to store the water. It depends on many factors. The quantity of water needed, the amount and pattern of rainfall and the surface area of catchment area are the criteria used in deciding the size of storage tank.

v. Water Treatment
The treatment operation depends upon the intended uses of rain water. Treatments for non-drinking purposes include simple filters, addition of chemical coagulants for flocculation and sedimentation. Fine filters and microbiological disinfection are only necessary for potable use, i.e. for drinking water. The disinfection can be achieved either by addition of chlorine or exposure of water to ultraviolet (UV) light.Chlorination is more commonly used. The fine filters need regular cleaning and maintenance.

In spite of installation of leaf screens and first flush diverters, dirt, rust, scale, bird and rodent droppings and airborne bacteria may still reach the storage tank.Therefore, even for non drinking purposes, it may be a good idea to have gravity settling of solids and filtration of dispersed solids. Optionally, fine filters may be installed prior to the end use.Consult with experts before adopting different water treatment methods. Have water tested by an approved laboratory periodically to monitor the water quality.

vi. The Distribution System for the Treated Rainwater

The treated water needs to be conveyed to the point of use. Proper distribution system is needed for this. If the tank is installed at higher elevation than the taps, the water will flow by gravity. Otherwise, we need to install a pump in distribution system. Effective plumbing is important for efficient rainwater collection and distribution.

Advantages of Rain Water

Collecting rainwater is not only water conserving, it is also energy conserving since the energy input required to treat and pump water is avoided. It also prevents soil erosion and flooding caused by runoff. It increases the availability of water. The quality of rainwater is better than other sources such as surface water or groundwater. Salts and minerals are picked up by water from soil and rocks on its way to surface water bodies such as lakes/rivers. Groundwater is contaminated by many pollutants due to indiscriminate use of pesticides and incomplete treatment of effluents by industries. In this way rainwater is better than these two types of water sources.

However, rainwater harvesting is location specific. Thus, rainwater falling in non-industrialized areas can be more pure compared to the rainwater in industrial areas where pollutant emissions are prevalent, or in agricultural regions where intensive use of pesticides and insecticides is prevalent. Rainwater is generally soft and can significantly reduce the need of water softening treatment.

Rain Water Harvesting

Rainwater harvesting is very old technique of water conservation in many parts of the world. We can find examples of rainwater harvesting systems in the history of great civilizations. As the name itself suggests, it involves collecting the rainwater and storing it. The technology can be as simple or as complex as required. The collected rainwater can be stored in metal or plastic tanks, which can be used for domestic or industrial purposes or it can be used to recharge the ground water.

Excessive tapping of ground water through numerous tube wells has led to a fall in water table in many parts of our country. To avoid the alarming fall of ground water table, the aquifer must be recharged by collecting every drop of rainwater,since that is the only source of ground water.

In India, traditionally we used to store the rainwater in ponds, which were used as surface water sources for drinking, irrigation and other purposes. However loss of water by evaporation is more in these. With increasing population, there is growing\ need of land for housing. These ponds are fast disappearing even in small towns due to this growing need of land for housing. This is leading to change in thinking.Now we have two options for better use of rainwater. In first option, the rainwater can be harvested and stored in a storage tank for latter use. The second option involves recharging the ground water with harvested rainwater. Various recharge structures are available to recharge the rainwater into ground. These are outlined here:

Pits : Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders,gravels and coarse sand.

Trenches: These are constructed when the permeable stream is available at shallow depth. Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m.long depending up availability of water. These are back filled with filter materials.

Dug wells: Existing dug wells may be utilized as recharge structure and water should pass through a graded filter or other filter media before putting into dug well.

Hand pumps: The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.

Recharge wells: Recharge wells of 10 to 30 cm diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells.

Recharge Shafts: For recharging the shallow aquifer which is located below clayey surface, recharge shafts are used. The size of recharge shaft is 0.5 to 3 m diameter and 10 to 15 m deep. After digging, these are back filled with boulders,gravels and coarse sand.

Spreading techniques: When permeable strata starts from top then this techniqueis used. Spread the water in streams/canals by making check dams and bunds. A percolation pond may be constructed in low-lying areas.

Watershed and Water Conservation

All of the land, which eventually drains to a common lake or river, is considered to be in the same watershed. Watersheds are defined by topographic divides which separate surface flow between two water system. All the rain that falls in a watershed flows in small streams. These small streams merge into a big stream. All such big streams flow in to a pond or lake or river. Agricultural and industrial activities in a watershed can affect the water quality of both surface water and groundwater. The pollutants find their way to surface water by runoff and to groundwater by infiltration. The human activities combined with natural forces shape the watershed. This combined effect affects the watershed landscape and its water quality. These, in turn, will affect our health and livelihood. Take the example of industrial activity which affects the water quality. The treated wastewater from industries is disposed off into environment. It reaches the water system of watershed and thus the quality of treated wastewater should be of acceptable level as stipulated by local regulatory authorities.

A watershed can be very large (e.g. draining thousands of acres to a major river or lake or the ocean), or very small, such as a 20-acre watershed that drains to a pond. A small watershed that lies inside a larger watershed is sometimes referred to as a sub watershed. The water conservation measures such as construction of check dams (small structures), percolation ponds and recharge wells should be based on topography of watershed. It is the social responsibility of the industries to conserving water to reduce wastewater volume. The water conservation will be economically gainful as well. Industries can recycle the treated wastewater in some cases to reduce the demand of freshwater. In this way watershed forms an ideal unit for management and sustainable development of its natural resources like water, soil, land and vegetation.

The Hydrologic Cycle

The hydrologic cycle describes the perpetual processes of motion, loss and recharge of the earth’s water. The never-ending exchange of water from the atmosphere to the oceans and back again is known as the hydrologic cycle. The processes can be visualized as shown in Figure. This cycle is the source of all forms of precipitation (hail, rain, and snow), and thus of all water.The water from rivers, ponds, ocean and soil evaporates while water stored in plants transpires to form clouds which store the water in the atmosphere. The vapour in the clouds condenses to result in precipitation. Like all other phenomena in nature, this cycle also derives its energy from the sun. Explanations of various terms used in the figure are given below.

i. Evaporation

Solar energy falling on earth heats up the surface water molecules. These energized water molecules break free from water surface to evaporate and rise as invisible vapour in the atmosphere.

Hydrologic Cycle

ii. Transpiration
All the plants emit water vapour through leaves. This process is named as transpiration. Actively growing plants transpire more vigorously. It could be as high as 5 to 10 times the water it can hold. It is physiological requirement of the plant.

iii. Condensation

The water vapours from evaporation and condensation rise. As temperature falls at higher levels, the water vapour cools and eventually condenses with tiny dust particles present in atmosphere as nuclei. These nuclei grow and agglomerate into clouds. These clouds are mobile and are driven by air currents in the atmosphere.

iv. Precipitation

If these clouds further rise in atmosphere, they get supersaturated with water and that water falls down as rain. If the temperature of surrounding is too low, then hail or snow fall results. All these forms of water getting condensed and falling on earth is called precipitation. The rainfall is more near the mountain ranges because they cause the clouds to rise in air.

v. Run off

Excessive precipitation or snowmelt during summer result in flow of water in treams to rivers or ponds. This visible flow of water on land surface depends on topography of watershed and is called run off. We will discuss watershed in next section.

vi. Infiltration

As the land surface is permeable, part of the precipitation or run off will infiltrate through the surface downwards. This infiltration water reaches the groundwater.

vii. Groundwater

Depending on geology of soil below the surface, the infiltration water is stored as ground water. This groundwater is brought to surface by digging wells for our use.Sometimes, the groundwater can flow into streams or into ocean. Groundwater hydrology is the science that studies the storage and dynamic movement of groundwater.