Industrial Wastewater Engineering

The first step of this project involved the evaluation of the suitability of process wastewater for discharge into the municipal sewer system. These wastewaters were periodically trucked away from the facility and disposed of as a special waste. Acheron was responsible for developing a sampling plan and performing wastewater sampling and analysis.

When the analytical results were compared with local sewer use and DEP-regulated limits, the need for industrial pretreatment was affirmed. Additional study demonstrated that chemical neutralization of the wastewater, followed by primary treatment including solids separation and separate disposal of sludge, would bring the wastewater characteristics within limits suitable for disposal in the municipal system.

The Corinna Sewer District (CSD) POTW was constructed in 1969 to treat a combination of 85 percent industrial and 15 percent domestic wastewaters. All industrial wastewaters are contributed by the Eastland Woolen Mill. In response to a lengthy history of POTW operations, difficulties including pollutant pass-throughs, elevated effluent-toxicity levels and permit violations, Eastland retained Acheron to perform a complete evaluation of the following items:

1. the industrial wastewater contributed to the POTW by Eastland,

2. the physical components of the POTW, and

3. operations at the POTW.

The resulting study included a complete chemical and toxicological evaluation of the industrial wastewater. This evaluation involved operation of various pilot plants under warm and cold conditions to assess wastewater treatability under seasonally adjusted circumstances. As a result of these investigations, Acheron identified chemical constituents contributing to sludge contamination, pass-throughs and effluent toxicity.

Because these constituents were not biodegradable in the POTW’s conventional secondary-treatment system, Acheron initiated a two-year chemical substitution program at the mill. This program altered the physical/chemical characteristics of mill effluent. Based upon these altered characteristics, Acheron then designed modifications of the pretreatment system and secondary clarifiers at the POTW. Since these changes were implemented, the facility has complied with virtually every permit condition, including the very stringent toxicity limits. Only the limit for coliform bacteria has occasionally been exceeded.

This project involved the design of a new 1.2 MGD extended-aeration system for Guilford of Maine’s textile manufacturing facility in East Douglas, Massachusetts. The existing industrial wastewater treatment plant utilized an aerated lagoon and one secondary clarifier to process the wastewater generated during manufacturing operations, prior to discharge into the Mumford River. Because of continuing problems with the lagoon liner and the operational inflexibility of the existing treatment process, Guilford retained Acheron to design a new treatment process that would enhance treatment of the process wastewater, increase operational flexibility and provide unit-process redundancy.

The modifications to the facility entailed construction of a new reinforced concrete equalization and aeration tank with a total volume of 1.2 million gallons. The new tank is divided into four compartments and is equipped with a coarse bubble, diffused aeration equipment. One tank is also designed as an equalization basin to provide chemical/flow equalization capability that did not previously exist at the plant.

In addition, the plant modifications included a new 50-foot diameter flocculating clarifier designed to work in series or in parallel with the existing plant clarifier. The new clarifier will provide Guilford with the operational flexibility to take one clarifier off line for maintenance without disrupting the treatment process. The new clarifier will also allow Guilford to achieve improved solids removal with the eventual goal of recycling the treated waters.

The total project cost was approximately $1.8 million, including engineering.

This project involved the design of a coarse-bubble diffused aeration system to replace an aging and failing static-tube aeration system for an existing aerated lagoon at the Hartland Municipal Wastewater Treatment Plant (WWTP). The existing system was over 20 years old and its centrifugal blowers were in serious need of replacement. The WWTP receives over 90 percent of its flows from a local tannery, whose operations are completely dependent on the continued operation of the WWTP.

Acheron evaluated the numerous alternatives available to replace the failing aeration system. Life cycle costs for the various alternatives, including capital, energy, and maintenance costs, were calculated and a recommendation was made to install a coarse-bubble diffused aeration system powered by three (3)-250 Hp centrifugal blowers.

Working closely with the Town and the tannery, Acheron designed the new aeration system. The aeration system was designed to include a dissolved-oxygen (D.O.) control loop for the centrifugal blowers that would allow the blowers to be throttled to achieve a pre-set D.O. level in the aeration basin. The overall project included a new coarse-bubble aeration system, three (3)-250 Hp centrifugal blowers, a new blower building, and modifications to the existing aeration basin to improve its hydraulic efficiency by creating a serpentine-flow pattern. The total project cost was approximately $900,000.

This four-year study of process-wastewater treatability was performed prior to initial discharge of a high-strength, potentially toxic industrial wastewater to the Guilford-Sangerville Sanitary District POTW, which was then being designed for use by Guilford of Maine and the Town of Guilford. The project’s goal was the development of a treatment scheme that would allow our client to meet the anticipated license limits of the POTW. These limits were expected to include conventional and non-conventional discharge parameters, such as toxicity limits.

The principal concerns of the District and its Design Engineers included the following:

1. development of appropriate design criteria for the aeration system at the POTW,

2. the potentially toxic effects of incoming industrial wastewater upon the biomass in the secondary-treatment facility,

3. treatability of the industrial wastewater under both summer and winter conditions,

4. pass-through of certain non-biodegradable constituents, and

5. POTW effluent toxicity.

Acheron’s responsibilities for this project involved design, construction and operation of a 1,000-gallon pilot plant, as well as four (4) smaller-scale pilot plants operated under warm and cold conditions. Samples were analyzed and progress was monitored for both standard operational approaches and non-conventional treatment technologies (including tertiary treatment and ultrafiltration). Pre- and post-treatment chemical flocculation was also investigated.

Data collected by Acheron during this study resulted in development of a process-chemical substitution program at the mill. This program was aimed at replacement of a non-treatable wastewater component with biodegradable materials. We also provided the POTW with design criteria for the proposed aeration system. The POTW was then constructed with only minimal pretreatment facilities, including flow equalization, screening and pH control. It has operated continuously since 1989 without a permit violation.

In response to difficulties experienced by the Ashland POTW, Acheron collected samples of industrial wastewater at L.W. Packard. As a means of assessing treatability, these samples were used as influent to a series of pilot plants designed to simulate the secondary-treatment components of the POTW. The plants were operated under both warm and cold conditions.

The pilot plant studies indicted that the wastewater would be treatable by Ashland’s conventional secondary treatment facility if minor modifications were made to the aeration basins. Because of sludge accumulations and hydraulic deficiencies in the existing aeration system, insufficient detention time was provided for adequate biodegradation of wastewater components. Since these modifications were accomplished, the POTW has operated in compliance with State and Federal Permit limits.

L.W. Packard, a woolen textile manufacturer in Ashland, New Hampshire, in the early 1990s realized that in order to survive in the textile business through to the next century, they would need to modernize and expand; however, their existing operations in the central village area of Ashland, New Hampshire, offered few opportunities for growth. Even modernizing was difficult because of limited space.

L.W. Packard decided, after carefully considering all the options, to purchase a large parcel of land on Route 132 in New Bedford, New Hampshire. In 1996, construction started on the multi-phased project for a new textile mill. The first phase was designed to house their new state-of-the-art carbonizer and scouring machine that is more efficient than any equipment ever used to carbonize and scour fine woolen fabrics.

At that point, L.W. Packard retained Acheron Engineering Services to assist them with the evaluation of water supply and wastewater disposal options for their new facility. L.W. Packard asked Acheron to complete the following tasks in evaluating water supply and wastewater disposal options:

1. To prepare an engineering study of the technical and economic feasibility of extracting up to 350 gallons per minute of cooling water from the sand and gravel aquifer under the site.

2. To prepare an engineering evaluation of the technical and economic feasibility of reintroducing approximately 350 gallons per minute of non-contact cooling water to the aquifer under this site.

3. Assuming Number 2 is feasible, to prepare design drawings and permit applications necessary to reintroduce the cooling water back to the aquifer.

4. To prepare an engineering evaluation of the technical, regulatory and economic feasibility of constructing an industrial wastewater treatment facility on the site with a discharge under I-93 to the Pemigewasset River.

5. To prepare an engineering evaluation of the technical, regulatory, and economic feasibility of constructing a pipeline for the conveyance of industrial wastewater into the interceptor sewer and wastewater treatment system owned and operated by the State of New Hampshire in Franklin, New Hampshire.

6. To prepare an engineering evaluation of the technical, regulatory, and economic feasibility of constructing a pipeline for the conveyance of industrial wastewater to the municipal sewer and wastewater treatment system owned and operated by the Town of Ashland, New Hampshire.

7. To prepare an engineering evaluation of the technical, regulatory, and economic feasibility of constructing an industrial wastewater treatment facility on site with discharge to the sand and gravel aquifer under the site.

When the studies described above were completed, the results were conveyed to L.W. Packard in a verbal report with several summary sheets, including estimated capital and annual operation and maintenance costs for each option.

Once L.W. Packard decided to proceed with construction of the first phase of the new textile plant, a series of wells for cooling and domestic water were installed. A subsurface wastewater disposal system was installed for the domestic wastewater. A subsurface infiltration system was designed and constructed to infiltrate approximately 350 gallons per minute of cooling water back to the aquifer under the site. The small amount of industrial process wastewater generated by their new carbonizer and scouring equipment is currently being trucked from New Hampton to the State’s wastewater treatment plant in Franklin. The first phase is now operating at full capacity. Plans for future expansion are currently on hold pending resolution of large scale wastewater treatment and disposal issues.

Acheron was retained by the Robinson Manufacturing Company to respond to exceedences of NPDES permit limits and the unfavorable results of a benthic evaluation performed on the receiving stream. A multifaceted investigation followed. Preliminary investigation indicated that the license-parameter exceedences could have resulted from three (3) possible causes:

1. the presence of an untreatable substance in the waste stream,

2. design inadequacies in the on-site treatment plant,

3. inadequacies in treatment-plant operations and maintenance.

The overall goals of the waste stream evaluation were to identify the chemical sources of excessive toxicity in Robinson’s effluent, to trace them to specific points of introduction in the manufacturing process, and to replace them with less toxic alternatives that would not impair the quality of the finished product. Bioassay testing was performed on separate waste streams originating in various departments of the facility. Samples of each waste stream were also evaluated for biodegradation performance and residual toxicity under pilot-plant conditions.

Through these evaluations, the pollutant of concern was traced and identified. Substitute materials were then obtained and subjected to pilot plant testing. The most promising substitute was successfully introduced into the actual manufacturing process and was adopted for use.

Acheron performed a complete evaluation of Robinson’s operations and treatment plant design. Of primary concern for plant design was whether the aeration system, as configured, was providing adequate detention time and whether the plant environment could be altered to improve settling of the mixed liquor. Other subjects of concern were hydraulic equalization and pH neutralization.

The evaluation suggested that most of the major components were adequately sized, but that operational strategies and structural configurations were not making the best use of available capacities. Consequently, the aeration basin’s interior walls were rearranged, two (2) new splitter boxes were added, return activated sludge lines were redirected and additional valving was provided. Other important upgrades included installation of pH control and chemical assistance to the clarifiers.

Procedures and conditions related to treatment plant operations and maintenance were also evaluated. Included in this study were process control procedures, reporting/record-keeping, sampling and analyses, and operator training. Among the deficiencies noted were mismanagement of system solids, under-use of process control indicators and lack of effluent quality trend charting. Because of the inadequacies in the existing monitoring program, proper data for institution of effective process control measure were unavailable.

To address this situation, Acheron prescribed and performed a monitoring and testing program designed to provide sufficient data to indicate a proper mode of treatment operations. A solids wasting schedule was instituted and sampling and laboratory analysis procedures were updated. An extended aeration mode of treatment employing microorganisms in the endogenous growth phase was initiated after the treatment facility was physically modified. A greatly expanded monitoring schedule was also implemented immediately, and Robinson’s operator received additional training.

One result of the multi-disciplined, thorough approach to this project was Robinson’s receipt of a special, first time award for excellence in Industrial Treatment Facility Operations. This award was presented by the Maine Wastewater Control Association. Candidates were nominated by the Maine DEP. Acheron has remained the primary consultant for the continued successful operation of this facility.

Because of difficulties experienced at the local POTW in treating incoming wastewaters, Troy Mills retained Acheron to investigate the pretreatment operations in effect at the manufacturing facility. The pH neutralization needed to be upgraded, but design and implementation of a new pH neutralization system did not eliminate treatment difficulties at the POTW. When a pilot plant investigation indicated that Troy’s wastewater was 100 percent biodegradable, the evaluation shifted to the POTW itself.

As a result of the extended study, Acheron found various aspects of the existing POTW design inadequate, particularly in terms of aeration. This system was upgraded and several additional engineering modifications were accomplished. These combined efforts restored the POTW to efficient operation.