Neutralizers & pH Neutralization Systems

Highly acidic or basic waste liquids from labs, industrial sources and rinsing operations can cause chemical attack on sewage pipework as well as operating problems in municipal waste treatment plants. Environmental regulations are written to avoid these problems by specifying that waste liquids must be near neutral pH before they can be released into any public sewer or body of water.

The pH value of a neutral liquid is 7, and the regulations generally establish an acceptable discharge range of 6 to 9 pH units. In most cases this requires the installation of an on-site neutralizing system.

However, pH control around the neutral point is notoriously difficult due to the logarithmic nature of the pH scale. Many facilities that generate acidic or basic waste liquids turn to ChemIndustrial as their source for the specialized process equipment and controls required for successful neutralization.

(Please consult ChemIndustrial's Chemical Theory section for a complete discussion of acid/base theory)

Neutralizer Skid

ChemIndustrial's Neutralizer Skid is perfect for small industrial processes and laboratories [Full Size Image]

ChemIndustrial neutralizers - integrated pH neutralization systems

A ChemIndustrial neutralizer receives, samples, measures and controls the pH of liquid discharged from a facility, then discharges successfully treated liquid to a sewer or a downstream process.

The neutralizer circulates a stream of liquid from a tank past a pH sensor, meters and mixes a neutralizing chemical into the circulating liquid by means of a venturi injector.

ChemIndustrial neutralizers are built in two basic configurations:

  1. One-way neutralization for correcting pH that always varies in the same direction from the required range
  2. Two-way neutralization for correcting pH that can vary either above or below the required range

ChemIndustrial neutralizers use reliable pumped venturi injection technology for chemical feed. Neutralizer controls are optimized for operation in the 6 to 9 pH range. ChemIndustrial's sophisticated control algorithms intelligently adjust the amount of neutralizing chemical added to the process as the system's pH approaches the neutralization point.

  • Reliable pumped venturi injection
  • Low component count
  • A complete, integrated package ready to install
  • Available with tank, or to integrate with owner's tank
  • Single vendor responsibility
  • Intuitive controls
  • Multiple control modes for difficult processes
  • Liquid circulation cleans the sensor
  • Prompted sensor calibration
  • On-board alarm system integrates with owner's controls
  • Optional modem allows remote operation and troubleshooting
Neutralizer featuring Autocalibrate

Autocalibrate™ (panel to left) is one of many advanced neutralizer options
[Full Size Image]

Skid-mounted neutralizer with tank

Skid-mounted neutralizers are perfect for small industrial processes and laboratories. These complete systems combine a neutralizing tank with ChemIndustrial's advanced controls and pumped venturi chemical injection technology to provide the mixing, pumping, pH sensing and chemical injection required to treat and discharge process waste streams.

ChemIndustrial skid-mounted neutralizers have small footprints, approximately 4 ft x 4 ft for industrial models. They are easily received and moved at the customer's facility.

Lab models have even smaller footprints for installation where space is limited (even under a lab bench!), and fit through tight doorways and aisles.

Configuration of a typical skid-mounted neutralizer (one-way, acid)
Larger neutralizing systems

ChemIndustrial skid-mounted neutralizers are sized for easy integration into many customer facilities, but a standard skid may not be large enough for high volume waste flows.

When the flow of liquid for treatment exceeds the practical capacity of a skid, we turn to other strategies:

Lab neutralizers
Small, semi-automatic lab neutralizers

ChemIndustrial offers smaller liquid waste neutralizers for individual labs. These systems neutralize automatically in an integrated tank, with manual tank inlet and drain controls. In these systems, liquids to be treated are added manually. A neutralization cycle is started at the press of a button and stops automatically when tank contents are fully treated. Then the neutralized liquid is discharged manually.

These systems are normally used in small labs where treatment quantities are low and equipment budgets are limited. A 45 gallon tank is standard, but other tank sizes are available.

Large, centralized lab neutralization systems

For larger volumes of lab waste liquid, ChemIndustrial's industrial neutralizers described above become the systems of choice for the treatment job.

For more information on lab neutralizers...

If you're considering a neutralizer for lab waste, complete the Lab Neutralizer Questionnaire (pdf) and fax it to ChemIndustrial. We'll review it and contact you with information on the appropriate system.

Neutralizer drawings

Following are schematics showing some typical applications of ChemIndustrial neutralizers:

Drawing 1 (pdf): A two-way neutralizer installation using existing sump
In this system the acidic/basic waste liquid drains from the customer's process into an existing sump at a low point in the customer's plant. The sump is retrofitted with a custom-built ChemIndustrial fiberglass grid deck that bridges the sump and incorporates level sensing instrumentation and two redundant, alternating, transfer pumps.

Pre-wired cables connect pump motors and level sensors to the ChemIndustrial control panel. After the retrofit is installed on the sump and equipment cables are connected, this unit behaves like a standard ChemIndustrial duplex Liquid Waste Transfer Station (LWTS).

The retrofit LWTS transfers waste liquid to a surge tank. A correctly sized surge tank uncouples the instantaneous flow of the incoming process liquid from the treatment rate of the neutralizer thus allowing the neutralizer to be sized to treat the average flow instead of the peak waste liquid flow. This usually allows a smaller (lower cost) neutralizer to be installed.

From the surge tank, liquid flows into the ChemIndustrial 2-way neutralizer by gravity via an on/off valve controlled by the neutralizer.

The neutralizer is capable of running in pure batch mode but it also has a second, more productive control algorithm: ChemIndustrial's Semicontinuous pH Control Algorithm™.

This opportunistic algorithm begins aggressive treatment of the waste liquid as soon as any becomes available, without waiting for the neutralizer to fill. The algorithm discharges liquid whenever pH is within the allowable discharge range. It ceases discharging and resumes treatment whenever pH drifts outside the control band.

This drawing also shows a typical application of ChemIndustrial's ChemWand® drum feeders to supply acid and base reagents to the 2-way neutralizer.

Drawing 2 (pdf): A two-way neutralizer with one or more distributed Liquid Waste Transfer Tanks

Drawing 3 (pdf): A two-way neutralizer with Liquid Waste Transfer Tank and distributed control system

Drawing 4 (pdf): A large lab installation with central sump

Drawing 5 (pdf): A large lab installation with distributed sumps

Drawing 6 (pdf): A simple one-way neutralizer with surge tank

Drawing 7 (pdf): A small under-bench lab neutralizer

Drawing 8 (pdf): A simple two-way neutralizer with surge tank

Drawing 9 (pdf): A ready-mix concrete facility
In this system the acidic or basic waste liquid drains from its source into an open settling pond.

Often the waste liquid originates directly from a washout operation. In other cases the liquid is storm water that carries dissolved material and fines from a yard or mining site. In both cases, regulations require the pH of the liquid to be brought into the neutral range before discharge.

The drawing shows an automated one-way neutralizing system as it is applied at a readymix concrete plant or a mineral processing site. The neutralizer's automatic control system starts and stops the pond pump to transfer pond liquid to the neutralizer. The neutralizer treats the liquid automatically and discharges the treated liquid. When the pond reaches low level the neutralizer goes into standby mode until more liquid becomes available.

One of the functions of a surface pond is to act as a settling basin for suspended solids. However, it is difficult to ensure rapid, 100% settling efficiency in the pond. To minimize downsteam problems from suspended materials, ChemIndustrial offers an optional hydroclone to dramatically reduce the amount of suspended material reaching the system outflow via the neutralizing skid.

Another ChemIndustrial option is outlet flow regulation. In many cases the regulations specify a maximum discharge rate and an allowable daily discharge volume as well as the acceptable pH range. A ChemIndustrial outlet flow regulator deals with these issues.

Automatic calibration is the newest feature available on ChemIndustrial's neutralizer and pH control systems. ChemIndustrial's Autocalibrate™ system simplifies pH control and neutralization by relieving operators of the need to manually calibrate the pH probe on a regular basis. Click here to learn more.

Many neutralizing system owners find it desirable to preserve a record of system operating performance. ChemIndustrial offers a range of recording options: circular chart recorders, free-standing paperless recorders or direct data transfer to a PC.

ChemIndustrial one-way neutralizers include a ChemWand® drum feeder to supply acid or base reagent to the neutralizer.


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