Cleaning is often essential on farms, when it’s all change in the cattle shed, for example, at the end of milking or when dirty machines need cleaning. Using pressure washers is a standard procedure, but new findings have come to light on whether hot water or cleaning agents and disinfectants should be used.
ECo-friendly and resource-saving use of cleaning agents and disinfectants plays an increasingly important role in cleaning processes, especially in food production. Maintaining healthy livestock is of critical significance in the manufacture of animal products. Production in conditions of global competition calls for continuous further development and optimisation of cleanliness and of pathogen eradication. The main focus is on minimising the resulting residues in the environment, and, above all, in the products themselves.
The Thuringian State Office for Agriculture (TLL) carried out cleaning tests to compare the use of hot and cold water. The research goal was to test the cleaning effect and above all the pathogen eradication effect achieved by pressure washers with improved technical features that eject water at temperatures of 80°C and more, at different water flow rates, working pressures and exposure times. All tests were conducted without the addition of cleaning agents and disinfectants.
They were performed as practical tests at the Thuringian Teaching, Testing and Research Farm in Buttelstedt and at Rhönland e.G. in Dermbach. The areas cleaned were evaluated in a laboratory. Swabs were tested after breeding for staphylococci, streptococci, gram-positive farm bacteria, spore formers and coli bacteria. In addition, the laboratory of the Animal Diseases Fund in Jena facilitated photographic representation of the incubated Petri dishes, as shown in the tables.
Detailed tests were undertaken of the effect of using hot-water machines for cleaning:
– Animal transport vehicles,
– Heavily soiled manure spreaders,
– Calf huts and
– The stalls of a pig-breeding plant.
Hot-water cleaning machines were used for all tests, and a pair-wise comparison was made between cold-water and hot-water cleaning. The technical parameters water flow rate, exposure time, working pressure, nozzles used and high-pressure lance were always the same. Temperatures were set on the machine, read off and checked with measuring devices.
The hotter the water, the better the outcome
An animal transport vehicle and a manure spreader were cleaned on the washing station with cold and, for comparison purposes, with hot water at 60°C. It should be noted that the main aim of cleaning the manure spreader was dirt removal. Bacteria eradication was not so important.
In the case of animal transport vehicles, both in internal transport and, most importantly, when transporting animals for slaughter or transferring them to other establishments, minimisation of pathogens plays a major role. The German Animal Transport Ordinance regulates c leaning and pathogen minimisation.
The analysis of cleaning results shown in Table 1 shows how the cleaning and pathogen reduction goals were achieved. This is particularly clear in the image documentation. In the case of the heavily soiled manure spreader, the visual impression of cold-water cleaning compared with hot-water cleaning were especially convincing (see table below). If pathogen reduction is not a priority, cleaning with warm water at approximately 60°C is adequate. For example, one could use warm water directly from a biogas plant.
The cleaning of calf huts places more stringent demands as regards the pathogen status of the huts after cleaning. When the next calf is placed in the hut it should not be confronted with bacteria from the previous inhabitant. Prolonged periods of vacancy make additional interim disinfection necessary.
For the purpose of testing, huts were cleaned with cold water, warm water at 60°C, hot water at 80°C and in each case swabs were taken after drying. There were clear differences in effectiveness. Cleaning with water at 60°C did not eradicate or minimise some types of pathogen. Cleaning with hot water at 80°C and with steam produced a very good effect. The huts and the floor were almost bacteria-free. After cleaning one must always wait until the cleaned surface has dried.
Final cleaning with steam always requires pre-cleaning both hut and floor with a high-pressure water jet because excrement, urine and straw residues must be removed after mucking out. Thus, if the object cleaned is required to be almost bacteria-free, steam cleaning always involves two operations, whereas pressure washing with hot water at 80°C (in the test at a water flow rate of 1,300 litres per hour and 200 bars pressure) requires only one operation. That saves a considera ble amount of time, also because less time is spent changing equip ment.
菌落：超过1,000 =原始细菌数量或无效减少，100至1,000 =细菌少量减少，30至100 =成功清洁和减少细菌，0至30 =细菌急剧减少，0 =无菌
菌落：超过1,000 =原始细菌数量或无效减少，100至1,000 =细菌少量减少，30至100 =成功清洁和减少细菌，0至30 =细菌急剧减少，0 =无菌
Economic evaluation of the various high-pressure cleaning systems must be based on the individual enterprise. Apart from power to drive the high-pressure pump, cold-water machines require no further energy input.
As the experiments showed, even water at 60°C reduces pathogens. If pressure washers are designed for inflow temperatures of up to 60°C or, better still, higher, heated water, for example from the thermal power station of a biogas plant, can be used. It is important to pay attention to the structural design of the high-pressure gun. It should be designed so that no hot water is passed through the handle. That type of design places too much thermal strain on the operator’s hand and prevents extended operation.
Hot-water pressure washers that can heat the intake water automatically to the steam setting require additional energy for this process, as much as 6 to 10 litres of diesel or heating oil per hour. In this case, water is taken from the existing cold-water pipe system. This higher energy consumption should be offset against the savings in working time, which can be reduced by half when cleaning calf huts, for example. Considerable further savings can be achieved because there is no longer any need for disinfecting measures in low-pathogen areas where specified and monitored cleaning management is practiced.
Heated pressure washers justify higher procurement costs because of their quality and performance. One should only buy machines that maintain the set temperature continuously, although a maximum deviation of 3% is tolerable. It should be made clear to manufacturers that these settings are required. In modern hot-water pressure washers, an eco setting is extremely useful. On this setting the instantaneous water heater always heats the water to 60°C regardless whether a different temperature or other parameters are set. The machine then achieves a perfect balance between cleaning performance and energy consumed.
A worthwhile aim for manufacturers of heated pressure washers should be to develop model versions that enable hot water from, say, milk refrigeration, biogas plant or biomass heating systems to be connected directly to the device and used. With incoming water at different temperatures, the device needs only to offset the difference in temperature between the incoming water and the setting, in this case 80°C.
Recommendations for use
Thorough and time-efficient cleaning and disinfection in all areas of agricultural production can only be achieved by using hot-water pressure washers. Cold-water models can achieve a certain basic degree of cleaning by means of high pressure and a large amount of water.
As soon as higher levels of fat removal or, indeed, bacteria reduction are required, they are largely ineffective, however. Using chemical cleaning agents to assist in the cleaning process with cold water is inappropriate.
The test series showed that hot-water pressure washers can achieve a drastic reduction in bacteria levels even without using cleaning agents and disinfectant solutions. In many cases, disinfectant usage can be reduced or the disinfection cycle protracted. This saving and the reduction in working time required usually more than offset the cost of using hot water. Buildings and equipment are also less subjected to chemical contamination. The risk of residues in agricultural products and the environment is minimised.
Compliance with statutory requirements such as for disinfection of animal transporters is of course essential, and operatives must work precisely as a precondition for success in cleaning and bacteria reduction.
Given the low impact pressure and energy density of steam, cleaning with the full amount of water, the highest possible pressure and at 80°C, is usually to be preferred. The energy density per unit of surface area, in other words the impact pressure and temperature, ensure swift and thorough cleaning and secure bacteria reduction.
There is thus a greater process reliability combined with a saving of up to two work operations. A minimum hot-water pressure washer requirement is a water throughput of 1,000 l/h and a jet pressure of 180 bar. Less will not ensure reliable results.
考虑到蒸汽的冲击压力和能量密度较低，通常优选是用足量的水、最高可能压力和80°C水温进行清洁。单位表面积的能量密度，也就是冲击压力和温度，是快速彻底清洗和并减少细菌的保证。因此，工艺可靠性更高，同时最多可减少两个工作操作。热水压力清洗机的最低要求是1000 l/h的水流量和180 bar的喷射压力。低于此则不能保证可靠的结果。
原文作者/Dr. Günter Beyersdorfer（郭琳根州农业办公室）