An automatic water sampler collects samples from a water source without requiring human intervention each time a sample is needed. Samplers can be programmed to collect samples at different intervals for different durations. The collected water samples can be evaluated immediately onsite, or they can be stored and transported to a facility's laboratory for analysis.
Facilities in many industries use automatic water samplers to help meet their required water quality standards. These facilities have seen a trend in recent years toward more heavily regulated water quality governance, more detailed permit requirements, and more thorough water sampling documentation.
Automatic water samplers provide facilities with detailed sampling data that is reportable and defensible. In addition, facilities have discovered several other benefits of using automatic water samplers:
By efficiently collecting and preserving water samples, automatic water samplers help provide accurate water quality data. This data aids facilities in making more informed decisions. Ultimately, these decisions can affect the safety and health of humans and other organisms that depend on water as a vital resource.
Before reviewing the different types of automatic water samplers, it may be helpful to first understand how automatic water sampling is different from manual water sampling.
Manual sampling, sometimes referred to as performing a "manual grab," requires minimal equipment. Low-tech manual sampling is done by simply placing a sample container into a water source, or its flow, and collecting a sample. Manual sampling can be a cost-effective solution for a facility with short-term monitoring programs or very infrequent sampling.
Facilities that conduct frequent sampling in multiple, distant locations often find manual sampling to be inconvenient. Manual sampling requires trained sampling personnel to be available to collect samples. In addition, some site environments pose safety concerns to sampling personnel. In these situations, facilities often prefer automatic sampling.
Automatic sampling uses a preprogrammed powered water sampler to collect water samples on a time-based or event-triggered schedule. For example, a water sampler can be programmed to collect water samples every day at 6 a.m. and 6 p.m. (time based), or a sampler can be programmed to start sampling every time rain begins to fall (event triggered).
Because of the ability to program the sampling and the convenience offered, automatic sampling is often preferred to manual sampling. Automatic sampling offers the convenience of unattended, long-term monitoring, thereby reducing the time and cost associated with frequent manual sampling. In addition, automatic sampling minimizes the possibility of human error in sample collection.
Automatic water samplers vary considerably in their technology and application, but they share the same components. These components are briefly described in the following sections.
The controller, or "brain" of the water sampler, is used to program and control the sampler. The controller usually has a keypad for programming the sampler and an LCD for providing status feedback.
The pump system moves fluid from the water source into the water sampler to collect the samples. Water samplers commonly use either a peristaltic or vacuum pump.
Sample containers hold water samples until they are evaluated or analyzed. A water sampler may deposit samples into a single sample container (composite sampling) or into individual sample containers (discrete sampling).
If samples must be chilled, a portable sampler's cooling chamber or a stationary sampler's refrigerator is used.
The following water sampler types and characteristics, as well as their advantages and disadvantages, are described in these sections:
Automatic water samplers use either peristaltic pump or vacuum pump technology. Both pump technologies move fluid from the water source into the water sampler so that the fluid can be collected.
In a peristaltic pump, the flexible tubing is squeezed to make the fluid flow through the tubing. The following are the steps used to measure and collect a water sample using peristaltic pump technology:
In a vacuum pump, negative pressure creates a vacuum that makes the fluid flow. The following are the steps used to measure and collect a sample using vacuum pump technology:
Automatic water samplers can collect either composite or discrete samples over time. In composite sampling, individual sample volumes are deposited into a single large sample container. In discrete sampling, individual sample volumes are deposited into individual small sample containers.
Composite sampling can provide a representative water sample for a certain period. Over time, a composite sampler deposits individual sample volumes into a single large sample container. The size of the sample container can vary. For example, a composite sampler could be used with a single 9 L container or a single 20 L container.
Discrete sampling is used to acquire multiple, distinct water samples over time. A discrete sampler deposits each sample volume into its own separate sample container. A stepper with distributor arm rotates among the sample containers and fills them one at a time.
The sample containers used in a discrete sampler are available in a variety of sizes, but a discrete sampler typically contains a set of sample containers that are uniform in size. For example, a discrete sampler could use a set of 0.5 L containers, a set of 1 L containers, or a set of 2 L containers. Because the space to hold the sample containers is finite, either many smaller containers or fewer larger containers can be used.
A variation on discrete sampling is multi-composite sampling. Multi-composite sampling uses a discrete sampler to deposit multiple sample volumes into a single sample container. The distributor arm then rotates to fill the next container in the same manner.
Automatic water samplers are either portable or stationary. A portable water sampler can be moved easily from one site location to another. A stationary water sampler is designed to remain at a fixed installation. Both types of water samplers can be used to collect either composite or discrete samples.
As the term "portable" implies, a portable sampler is one that can be moved easily from one sampling site to another. (If required, however, a portable sampler can remain at a single site.) Because of their smaller size, portable samplers may also be used at space-restricted locations.
As the term "stationary" implies, a stationary sampler is designed to remain at a particular sampling site for an extended period. Although a stationary sampler is often considered a permanent fixture, it can be moved from a site.
Automatic water samplers may or may not be used to chill their collected water samples. Chilling options are available using either a portable or stationary sampler; however, the samplers' methods for chilling samples are different.
Chilling water samples significantly reduces the rate at which chemical reactions and biological phase changes occur in the samples. Consequently, water samples are more accurate and representative of their water sources.
Stationary samplers typically chill samples using a refrigerator. When a refrigerator, powered by an ac power source, is used in a water sampling system, samples can be kept chilled for months. Water samples are typically kept at a temperature of 4 degrees Celsius (39 degrees Fahrenheit).
Portable samplers typically chill samples using ice placed in a cooling chamber. Many portable samplers are equipped with a cooling chamber in their base. The cooling chamber has an insulated cavity that can be filled with cubed or crushed ice. The use of ice can keep samples chilled for up to 24 hours prior to the samples' collection for analysis.
Stationary samplers without a refrigerator, as well as portable samplers used without ice, do not chill their water samples. Consequently, the water samples may be more susceptible to biological or chemical changes caused by changes in the ambient temperature.
The intention of this section is to provide a general overview of automatic water samplers. The following list provides some additional resources regarding water sampling and automatic water samplers:
Number of FAQs related to Water Samplers: 44
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With some sampler models, the automatic sampling program will automatically resume. With other models, it may be necessary to restart the system. For details on this topic, consult the instruction manual for the particular water sampler.
When a facility uses an automatic water sampler with a datalogger, the facility has more flexibility. For example, a facility can use various sensors to take many different measurements at the same time. These measurements can be analyzed onsite, in a laboratory, or at both locations.
Horizontal and vertical distances should not be considered separately because they work together to affect velocity. As the liquid moves across and up, it must be pumped with enough force to maintain the desired velocity for representative sampling.
To check the external battery’s voltage, connect a metering device to the battery. Keep it connected for several seconds to allow the device to level out. If the voltage is below 12.3 Vdc, it may be necessary to recharge the battery.
Replacing a battery is a quick process that will not cause the sampler to lose its programmed settings and information. The control panel has an internal battery and a small amount of memory that will preserve the information while the battery is replaced.
Automatic water samplers are typically tested at sea level, and their performance varies depending on the altitude at which they are actually used. Higher altitudes decrease the vertical lift capabilities of samplers. For high-altitude needs, consult with a water sampler supplier to build an appropriate system.
If a water sampler is used with a datalogger, the datalogger can be programmed to notify sampling personnel if a water sampler fails to collect a sample. The notification can be made through a variety of methods including an alarm, bell, whistle, light, etc. Additional notification options are available when a communications peripheral is used.
In a situation where a battery must be used, it is important to sustain power to the water sampler—especially when the battery begins losing a significant amount of charge. Sampling personnel need to manually replace depleted batteries with a ready supply of fully charged batteries.
The frequency with which the batteries need to be replaced may be reduced by using solar panels. Solar panels are only a practical option, however, if there is enough available, consistent solar radiation at the sampling site.
If it is difficult to replace the batteries, solar power is not a practical option, or the water sampling system’s power requirements are great, then a deep-cycle rechargeable battery may be a suitable option.
How long the controller’s internal 3.6 Vdc battery lasts depends on how long it remains in disuse, how long it is in use, and the complexity of the running program. Typically, the internal battery should provide several years of continued service.
If water sampling at a particular site has not been conducted before and the facility is unaware of what is in the water source, the facility should collect a water sample and have it tested in a laboratory. This information can be used to select water sampling equipment that is appropriate for the application before beginning a sampling program.