Liquid autosampler

waterwastewaterautomatic

Overview
Automatic autosamplers collect representative wastewater samples for laboratory quality testing. Collection modes include time-proportional, sample-volume proportional and flow-proportional sampling. Units are available as stationary (mains-powered) or portable models with different feeder and pump configurations.

Applicable regulations

• Regulation on substances particularly harmful to the aquatic environment and conditions for discharge of sewage and rainwater (example national regulatory references)
• Regulation on substances requiring water permits when introduced in industrial sewage (example national regulatory references)
• Regulation on obligations of industrial sewage suppliers and conditions for introducing sewage into sewage facilities (example national regulatory references)

Sample dosing – direct and indirect
Samples must remain representative and unmixed. Common feeder types are wheel feeders (often requiring an intermediate tray) and XY feeders. Wheel feeders are simpler but may need tray changes when bottle size changes. XY feeders place bottles without intermediate trays and offer greater flexibility at higher cost. Circular feeders with trays require regular cleaning and increase the risk of cross-mixing samples.

Pump type
Two pump families are used:

• Peristaltic pumps – allow direct collection proportional to flow by counting revolutions; sensitive to solids and contaminants that can block tubing, which may cause inaccurate sampling. Best for treated effluent.
• Vacuum pumps – measure volume via sensors corresponding to actual flow, more resistant to contamination and suitable for inlet and intake-station sampling; generally more expensive.

Sample storage temperature – active and passive cooling
Samples should be kept approximately 0 °C to 4 °C during collection. Stationary units typically use active 24 h refrigeration. Portable units require robust cooling, insulation and high-capacity batteries; many portable solutions use passive cartridge cooling, which can fail at elevated ambient temperatures and risk non-compliance with accredited measurement protocols.

Construction

• Durable stainless-steel housing – preferred for outdoor durability under sun, rain and temperature cycles; plastic housings are cheaper but age faster under UV and low temperatures.
• Separation of sampling chamber and electronics – recommended to position the control/electronics compartment above the sampling chamber to avoid flood damage.

Application place – stationary and portable models
Stationary autosamplers are typically installed at treatment-plant inlets/outlets or at pumping stations. Portable autosamplers are used for temporary monitoring and offer different feeder configurations; they face greater challenges for reliable active cooling and power supply.

Additional information
A technical selection guide (PDF) and checklist for purchase are typically provided to assist specification and procurement.

Technical specifications

• Sample collection modes: time-proportional, sample-volume proportional, flow-proportional
• Feeder types: wheel feeder (may require intermediate tray), wheel feeder with intermediate tray, XY feeder
• Pump types: peristaltic (counts revolutions, sensitive to solids), vacuum (volume sensor, more contamination-resistant)
• Recommended sample storage temperature: approx. 0 °C to 4 °C
• Cooling: active 24 h refrigeration recommended; passive cartridge cooling may be insufficient for extended high ambient temperatures
• Housing: stainless steel preferred for outdoor durability; plastic housings are less durable but cheaper
• Design best practice: separation of sampling chamber and electronics (electronics above sampling chamber)
• Deployment: stationary (mains-powered) and portable (requires batteries, insulation, effective cooling)