A Mammoth of a Groundwater Chemical Treatment Application

May 14, 2015
Drinking water resources for Mammoth Lake, a resort town nestled in the Sierra Mountain Range in northeastern California, consist of nine wells and fresh water from Lake Mary, which is situated above the town. Mammoth Community Water District developed one surface water and two groundwater treatment stations to treat the drinking water. Arsenic is present in the well water, so the District installed ProSeries-M M-3 peristaltic metering pumps from Blue-White to assist in the treatment of the water and removal of the arsenic.

Mammoth Lakes is a resort town nestled in the Sierra Mountain Range in northeastern California. Known for winter and summer tourist activities, the town experiences a high seasonal demand on its water resources during tourist influxes.

The town's drinking water resources consist of nine wells and fresh water from Lake Mary, which is situated above the town. Mammoth Community Water District developed one surface water and two groundwater treatment stations to treat the drinking water.

Arsenic is present in the well water, so the District installed ProSeries-M® M-3 peristaltic metering pumps from Blue-White to assist in the treatment of the water and removal of the arsenic.

The District installed ProSeries-M M-3 peristaltic metering pumps to assist in the treatment of the water and removal of the arsenic.

Mammoth Water District utilizes sodium hypochlorite (NaClO) and ferric chloride (FeCL3) in a multi-step arsenic removal process. With the injection of these chemicals into the raw groundwater, the arsenic molecules transform into a precipitate that can then be filtered out of the water.

Water in one of the wells requires a higher concentration of chemical for optimum arsenic removal. Operators discovered that segregating this well during treatment led to an overall reduction in chemical consumption and related cost. The treated water could then be reintegrated with that of the other wells.

Originally, the well stations utilized solenoid-style pumps; however, it was found that the off-gassing nature of liquid NaClO created vapor lock in the pumps. The peristaltic design of the ProSeries-M allows the excess gas accumulation to be pumped through the tubing, while also maintaining smooth, accurate and constant flow rate with no potential for vapor lock.

Additionally, when solenoid diaphragm pumps were used, the chemical tank required constant vigilance. If fluid volume levels fell below the level of the pump head, the pump became susceptible to suction lift errors, including loss of prime. In the case of the ProSeries-M, the pump head serves as a check valve: No matter the level in the chemical tank, the peristaltic pump has reliable suction lift and will not lose prime.

Utilizing the pumps' 4-20 mA input, the District was able to set desired dosage in the SCADA based on the incoming flow of water to the plant. The ProSeries-M is able to handle fluctuations in feed demand, keeping chemical injection at a consistent ratio.

The ProSeries-M design includes the built-in, patented Tube Failure Detection system (TFD; U.S. Patents 7,001,153 and 7,284,964), which is able to detect a wide range of chemicals and is designed to disregard pump-compatible fluids such as water and lubricants. If there's a rupture in the pump tube and a chemical is detected in the pump head, the pump will automatically shut off and energize a relay, permitting communications with external equipment such as an alarm or a SCADA system. The chemical must be cleaned from the pump head before the pump will restart.

ProSeries-M M-3 is capable of feed rates to 33.3 GPH/126 LPH, with a 10,000:1 turndown ratio. Maximum pressure rating is 125 PSI/8.6 Bar.

Blue-White is exhibiting at AWWA's ACE15 expo in Booth 2513.

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