WSU Tree Fruit Research & Extension Center

Postharvest Information Network

Sunday, March 24, 2019

WSU-TFREC/Postharvest Information Network/Wastewater Sampling Techniques

Wastewater Sampling Techniques


The General Wastewater Discharge Permit for Fresh Fruit Packers is now a part of our business operations. The federal Clean Water Act (CWA) provided an opportunity for utilities receiving water from industrial clients to require the upstream wastewater contributor (pre-discharger) to monitor the quality of wastewater being delivered to the local Public Owned Treatment Works (POTW). The POTW is ultimately responsible for the effluent discharge in to the local rivers and streams and this CWA provision created a means of holding pre-dischargers accountable for their contribution to the facility effluent load.

Why a General Permit?

A General Wastewater Discharge Permit is the most efficient way for the Washington State Department of Ecology (DOE) to administer a blanket set of wastewater quality discharge criteria to a similar industry. We appeared to be a fairly homogenous industry, with many post harvest practices in common. Also, this is the DOE's first "successful" attempt at regulating a whole industry with a general permit instead of individual permits. This saves the DOE significant staff time, and theoretically reduces our permit fees. The (in) efficiencies of the system are under considerable discussion.

Therefore, in a world where perceptions are everything, we have chosen, as the first industry to have wastewater industry wide discharges regulated, to take a proactive approach in our fruit packing operations. At this global economically sensitive time, we could be perceived as the local industrial capitalist taking profits at public and environmental expense. And during this politically sensitive time, we could be seen as busy, isolated, uncaring and perhaps even resistant to environmental responsibility, as we potentially use chemicals with seeming disregard for nature. Some folks could see us as not taking the environment as a serious concern.

In contrast to these perceptions, we most certainly are environmentally responsible and this permit offers a formal opportunity for the tree fruit industry to prove our environmental stewardship. We most certainly are active members of our communities, often our packing shed is the hub of the local economy and we pay our fair share of taxes, fees and cost-shares. People who are reasonable, educated and concerned staff our warehouses. We are neighbors, who live in the local community, "they" are us. Indeed our fruit industry uses chemicals responsibly, in order to pack, store and ship a highly perishable product to our domestic and foreign markets. The chemicals we use are under constant scrutiny from a multitude of regulators and environmental groups. To the point that we are under more restrictive constraints than imports from our foreign trading partners. We routinely document our chemical inputs and outputs and monitor our process control and safety requirements to meet industry standards.

Proactive compliance with the Fresh Fruit Packer Wastewater Discharge Permit gives us the opportunity to demonstrate our long-term concern for the environment. Building understanding and trust with folks concerned about water quality and agriculture is part of our assignment as we go about the mechanics of compliance with this General Wastewater Discharge Permit for Fresh Fruit Packers.

The sampling technique and frequency for wastewater quality analysis according to the Washington Fresh Fruit Packers General Discharge Permit, is determined by the source of wastewater from storage and processing operations.

The normal waste streams (effluent sources) from our fresh fruit packing plants are:

  • Dump tank water (high pollutant load)- pear packers
  • rocess water - all fruit packing operations
  • Drencher liquid - apple / cherry post harvest treatments
  • Rinse water - all fruit packing operations
  • Non-contact cooling water (low pollutant load) - storage facilities

Note that as we go down this list the quality of water improves.

The allowable Treatment or Disposal Methods (TDM) for the discharge water are:

  • Lined Evaporative Lagoon - Lined holding ponds, solids removed infrequently.

  • Dust Abatement - Requires a Road Management Plan to determine proper application rates.

  • Land Application - Irrigation systems or high frequency tanker trucks. The loading rate of pollutants is routinely monitored.

  • Public Owned Treatment Works - Your local sewer plant can accept a specific load of pollutants.

  • Percolation Ponds - Unlined earthen ponds with a slow percolation function.

  • Surface Water - nearby ditches, creeks, streams, rivers, lakes.<.p>

Note that as we go down this list the water allowed to be discharged must be of higher quality.

Therefore, if the quality of water determines the allowable discharge method we know that our highest quality water, generally non-contact cooling water (NCCW), can be discharged to the surface water. This is because NCCW is not likely to contribute to the degradation of the water it is being discharged to. Non-contact Cooling Water has very low Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD) and Chlorides (Cl). The pH is neutral and there are no fungicides or toxic materials.

Our poorest quality waters, those discharges with the highest pollutant loads are to be discharged to the land. The soil's natural absorption processes and its ability to breakdown contaminants can mitigate the pollutants. These discharge waters usually have higher TSS, TDS, BOD, heavy postharvest materials or higher Total Residual Chlorine.


Before beginning the actual sampling process, there are a few housekeeping issues to address:

First, we must diagram the system and determine what sampling points will represent the system, and the processes going on inside the warehouse operation. This diagram and its updates should be filed with the Permit application. Significant plant infrastructure modifications such as added packing lines, waste water discharge outlets relocated or update etc. should be retained as a file copy, so that all staff who are responsible for the sampling and interpretation of data can recap or trouble shoot the data efficiently.

Then, we need to set up a logbook, which is a gathering place for all system background information. It contains the schematic warehouse and storage system diagrams, as well as the identification of the specific sample sites and why they were selected. Behind the warehouse schematic, the logbook should have the following information:

  1. A table of contents - to easily access

  2. Chemical inputs

  3. On-site water quality data

  4. Laboratory data

  5. Problem diary

  6. System observations (lagoon freeboard record, running Fuji's, late storage fruit with high incidence of rots, storm water events, etc.

  7. Interpretation of data

  8. Copy of the environmental compliance plan.

All data is to be entered in ink, dated and initialed. If an error is made, it is to be crossed out and initialed. Logbooks should be hardbound with sequentially numbered pages. A template is available from our laboratory.

After the logbook is initiated, the sampling schedule and laboratory arrangements should be made. The accredited analytical laboratory will be familiar with the required testing procedures. You will perform the on-site analysis of pH and Total Residual Chlorine, as well as the calibration and maintenance of this testing equipment. Record on-site data based on the frequency described in the permit for the TDM you are using.

Sampling and interpretation of the data will be simplified if the logbook is maintained and the system observations are recorded. This is called process control.

Note: There is a process control program, available to the fruit industry through the USDA section in charge of inspections. The program is called Partners In Quality (PIQ). The program was initiated at the request of fresh food commodity industries, which were seeking relief from inspection charges. The program requires that a fresh food packing operation develop a quality control manual, which documents all aspects of the operations inputs and outputs. The inspection schedule and fees are significantly reduced if the operation can "prove" that its QC program controls the quality of the process.

This is in line with an international move in the manufacturing industries which subscribe to the specification of the International Standards Organization (ISO) so that products traded and used throughout the world are of a uniform consistency brought about by specific process control criteria. This program was outlined by Leanne Skelton of the USDA at this seminar.

The most tedious or difficult portion of the compliance with the General Wastewater Discharge Permit for the Fresh Fruit Packers is the paperwork and logbook maintenance. This is a challenge for several reasons:

  1. Non-certified Wastewater Treatment Plant Operators
    We have no formal training. In other industries, the staff routinely in charge of wastewater discharge operations, goes through intensive training on chemistry, process control and laboratory methods.

  2. Seasonal Operation
    This creates a higher staff turn-over in the positions responsible for this type of regulatory responsibility as compared to other industries.

  3. Moderate Priority for Management
    In the relative scheme of free market conditions, this issue does not appear to be critical to management.

  4. Regulatory Discomfort Regulatory discomfort is evident and the permit seems complex and over burdensome to the untrained eye. In reality, we have a fairly sweet deal with the Department of Ecology compared to other industries. Our laboratory has taken the lead in trying to facilitate the "field-implementation" of this permit in as "friendly" a manner as is practical, using: scheduling; education; outreach and sampling services.


    Samples are considered representative if the sample meets these criteria:

    1. Mimics the volume and nature of the discharge

    2. Reflects the normal operating cycle

    3. Is downstream of pre-treatment and upstream of the TDM

    4. Is sampled using the grab (discrete) or composite technique.


      Grab samples are used to sample wastewater destined for the TDMs of Dust Abatement and Land Application (infrequent discharges only). Grab Samples are discrete samples per discharge event. When taking grab samples be sure to agitate the solution to create a representative mix. Take one sample.

      Composite samples are used to sample wastewater destined for the TDMs of POTW's, Percolation Ponds and Surface Water (frequent discharges). Composite samples are collected over a period of time within the same shift. Take one sample per hour for an 8-hour shift. Thus you will have 8 samples of 125 mL each (sub-sample bottle) to make a 1 liter composite solution.

      Routine sampling is not required under the following conditions:

      1. Closed Loop Systems - sample at time of the annual purge, (TDS etc will be very high).

      2. Lined Evaporative Lagoons - sample only the final sludge for land applications or landfill disposal.

      To get the best data:

      1. Sample early in the week / month / quarter. This allows adequate time to re-sample a system, which is out of control, and modify internal processes.

      2. Document all process conditions during sampling.

      3. Fill all containers and complete forms. Indicate source of wastewater and TDM, i.e., Process POTW

      Holding Time

      Holding time is the time interval between when the sample has been taken and the analysis performed. Holding time is an important consideration for water quality data to be submitted to a regulating agency. Examples of holding time are:

      Some of the water quality analysis must be performed routinely on-site while other test must be done in a laboratory.

      The analysis of Flow, pH and Total Residual Chloride must be done on site. Equipment is available for these analyses and each instrument must be calibrated and standardized before each use. Electrodes and buffers must be replaced with frequently to ensure accurate data. For example, pH is one of the most important and quickly determined measurements, which can tell you if your process is our out control. Optional on-site sampling services performed by an accredited lab are also available. The waiver for non-accredited staff performing on-site analysis for this permit pertains only to the employees of the warehouse. Laboratory personnel must be accredited by the WADOE for sampling and on-site analysis on a contractual basis.

      The concentration of Total Chloride, Sulfate, Total Suspended Solids, Total Dissolved Solids, BOD, and Fungicides must be determined by an accredited laboratory. You should require the following from laboratory accredited by the WA DOE: qualified staff, standard methods, a specified level of Quality Assurance and acceptable results in a refereed performance evaluation.

      Fungicide Analysis (including DPA, TBZ, SOPP) - Fungicide content must be analyzed quarterly for waste water to: POTW, Percolation Pond, Land Application (TBZ all). Waste water can be analyzed annually if it is going to: Land application (DPA/TBZ), or Dust abatement (SOPP).

      Be certain to apply waste water containing fungicides/anti-oxidants according to your Land Application calculation or Dust Abatement - Road Management Plan. Apply materials only at label rates, agitate vigorously before distribution. If analysis exceeds allowable label rate, adjust application rate on Road Management Plan. Rates listed for application in the General Permit were determined by performing a toxicity test for our fruit industry with various materials. Please abide by the established rates for road management plans in the interest of environmental awareness. A certified soil scientist can help you calculate a site and matrix specific Road Management Plan.

      Analytical Data

      Factors which influence BOD analytical data include - organic debris, sugars, spore count, anaerobic conditions, oil and grease.

      Factors which influence TSS and TDS data include - organic debris, dirt/duff, minerals in water and soils, heavy metals.

      A review of Fresh Fruit Packing General Permit wastewater discharge permit violations shows that TSS, TDS and pH are the most common water quality violations where discharges were sent to Surface water, POTW's and Percolation Ponds. These three water quality parameters (TSS, TDS, and pH) can be modified without major financial warehouse expenditures by:

      1. Timely corrections to our process control

      2. Consistent sampling and on-site analysis

      3. Documenting conditions and reporting data consistently

      Benefits of good quality data

      1. Improved Process Control

      2. Assist with Chemical Registration Process

      3. Regulatory Equilibrium ~ We create a vested bargaining position with regulators.

      4. Public Proof of Environmental Stewardship

Laura Laurent Mrachek

Cascade Analytical
Wenatchee, WA

14th Annual Postharvest Conference,
Yakima, Washington
March 10-11,  1998

Tree Fruit Research & Extension Center, 1100 N Western Ave, Washington State University, Wenatchee WA 98801, 509-663-8181, Contact Us