Projects can be delayed or even cancelled if a developer does not have the means to provide adequate wastewater treatment for a site. In some cases developers rely on linking new sewers to the municipal wastewater treatment plant (WWTP), or expanding the existing conventional plant to accommodate the projected flow. But existing plant processes may not be able to handle the variable flow rate or harsh composition of the new wastewater stream and the resultant effluent may endanger the environment or area residents with poor quality discharge. Distance from the central WWTP may be another obstacle and if the site is too far away, a municipal sewer pipe could be cost prohibitive or nearly impossible to install due to obstructions such as land features, highways, and other buildings.

In such cases, land developers turn to onsite systems, also known as decentralized sewer systems, and must evaluate and select the best available wastewater treatment technology to meet regulatory requirements for discharge or reuse, while maximizing land use for construction and occupancy density.

Membrane Bioreactor Plants Provide Quick Fix
Onsite wastewater treatment with membrane bioreactor (MBR) systems is rapidly becoming the preferred method for cost-effectively meeting or exceeding the wastewater discharge or reuse requirements at non-sewered land development projects. These compact systems are increasingly being installed to service land development projects such as residential properties, hotels, resorts, shopping centers, office buildings, airports, and campgrounds.

One such system is ZENON’s pre-engineered Z-MOD™ packaged plant that can be quickly delivered and installed at virtually any site and can mitigate many of the wastewater permitting issues that land development projects face.

Conventional onsite treatment options such as septic systems, typically use a sizeable parcel of land since they require drainfields and adequate clearance from neighboring properties. Land developers can often increase occupancy intensity, accelerate the permitting process and reduce or eliminate hydrogeologic studies by implementing an advanced treatment process such as Z-MOD™ membrane bioreactor systems.

Robust Systems Provide High Quality Effluent
Z-MOD™ systems provide compact, cost-effective and easy-to-operate solutions for development projects with average daily flow of 1,000 GPD to over 2 MGD.

Reinforced, hollow-fiber ultrafiltration (UF) membranes are at the heart of Z-MOD™ systems. The membrane fibers are combined with biological wastewater treatment processes to eliminate the need for primary and secondary clarifiers—instead providing solids separation by filtration rather than settling. This means that MBRs can produce high quality effluent at all times, regardless of the settling characteristics of the sludge. Since sludge settling is not required, MBRs can operate at much higher mixed liquor suspended solids (MLSS) concentrations, typically in the range of 8,000 to 15,000 mg/L. This enables the system to function with a relatively small bioreactor volume, and considerably reduces capital and operating costs since less land, fewer components, and a smaller physical plant is required.

Hollow-fiber membranes are immersed directly into the mixed liquor and draw treated effluent into the fiber using a gentle suction. The membrane acts as a physical barrier, preventing suspended solids and pathogens from entering into the final effluent. MBR treatment works produce tertiary quality effluent that has very low levels of BOD, nitrogen, phosphorus and suspended solids (See Table 1). The ultrafiltered effluent may then be safely discharged into the environment or reused for any non-potable application.

The simple design of an MBR system enables complete wastewater treatment to be carried out in one or two steps and significantly reduces the operational equipment that the plant requires. A typical MBR wastewater treatment plant includes pretreatment for trash removal, membrane cassettes, bioreactor, permeate pumps, blowers for process and membrane scouring, and clean-in place equipment for membrane maintenance.

As effluent discharge requirements become increasingly stringent, many communities are considering advanced wastewater treatment technologies to ensure regulatory compliance and to preserve environmental health. There is also a growing need to conserve dwindling potable water supplies with progressive water reuse programs. By restoring wastewater to reuse standards, communities and industry can produce high quality reuse water for non-potable applications such as irrigation, industrial process water, or groundwater recharge.

Small Footprint, Discrete Design
New Z-MOD™ facilities can be constructed in virtually any location and can occupy as little as 1/5 of the space that a conventional WWTP requires, offering significant savings in land acquisition and construction costs, and maximizing occupancy on a parcel of land. Moreover, the small space requirements and modular construction provides a great deal of flexibility in design. Often the entire WWTP can be enclosed within a portion of the building that the MBR services, or within a small, separate building. Buildings can also be architecturally crafted to blend in with the surrounding area. When completed, the discreet design, low odor, and quiet operation of MBR plants makes them barely noticeable to passersby.

The operation of an MBR system is highly automated, and most small systems do not require full-time operators, as system performance can be monitored remotely. Fibers can be easily cleaned with a clean-in-place method or using an optional backpulsing process that delivers permeate water back through the membranes. This dislodges any particles that may adhere to the membranes. Intermittent aeration of the membranes is also used to scour debris from the fibers and provides mixing within the process tank to maintain solids in suspension. In-situ membrane cleaning can also be automatically performed if membrane permeability falls below a specified level.

ZENON offers the industry’s largest selection of packaged UF water or wastewater treatment plants, enabling developers to select the system configuration and capacity that best meets their current needs and provides a modular architecture that can be easily expanded to accommodate future demands.

Hundreds of small MBR systems are currently providing localized wastewater treatment to communities, industries and recreational facilities in the US and throughout the world. The following summaries provide a brief overview of various MBR applications that have enabled advanced wastewater treatment for land development projects.

Fallingwater – Mill Run, PA
In November 2003, Fallingwater, Frank Lloyd Wright’s architectural masterpiece, replaced an aging septic system with a Z-MOD™ packaged plant. Concerns had been raised that the septic system might soon fail and discharge sewage into Bear Run?a pure and environmentally sensitive exceptional value stream that tumbles over the waterfall beneath the home’s cantilevered floors. The 8,840 GPD system is housed in a separate 1,800 square foot building discreetly located away from the facility. The system recycles up to 70 percent of the wastewater that is produced by the facility’s 140,000 annual visitors and reuses it as flush water in the Visitor’s Pavilion. Any excess treated wastewater is used for irrigating the surrounding gardens.

The Manor – North Fulton County, GA
This prestigious site is Georgia’s first golf and country club community to offer residents a drought-proof supply of reuse water for irrigating lawns, common areas, and a 180-acre signature golf course. Each of the community’s planned 600 plus homes will be equipped with a dual water system—one supplying potable water, and a separate purple-pipe system to deliver reuse water.

An enhanced Z-MOD™ package plant provides wastewater treatment for up to 500,000 GPD and supplies reuse water for irrigating the extraordinary lots which are one acre and larger. This assures residents of an unlimited supply of water even during hot, dry summer weather, and aids conservation efforts by reducing demand on potable water supplies.

The extremely compact wastewater treatment plant is discretely styled to appear as a farm barn and is located on the golf course property. Strict odor control and noise abatement make it virtually undetectable to residents and visitors. Although this privately owned and operated plant currently serves The Manor community only, it has built in treatment capacity to provide an additional 300,000 GPD of wastewater treatment and resultant reuse water to residences and businesses in the surrounding area.

Forsyth County has recognized the exceptional quality of the reuse water produced by the Z-MOD™ system.

York Region Works and Transportation Building – East Gwillimbury, Ontario

The York Region Works and Transportation Centre in East Gwillimbury, Ontario, a recently constructed municipal building that will be occupied by approximately 500 employees daily. Although the development is on industrial land, developers faced a nearly impossible task of connecting the facility to the nearest municipal sewer pipe, which is about one mile away and lies on the other side of a major highway. An onsite treatment system was the only way for developers to provide wastewater treatment for the building.

A Z-MOD™ packaged plant made it possible for developers to accelerate the permitting process and implement an innovative water recycling system that minimizes septic requirements, reduces discharges to surface or sub-surface receiving sites and eliminates the need to conduct a hydrogeological survey. Upon presentation of design parameters and capabilities of the proposed system to regulatory agencies, the permit approval process was accelerated from six months to just 45 days, and saved York Region hundreds of thousands of dollars in additional assessment and consulting fees. SLDT