Containerized Membrane Bioreactor (MBR) Wastewater Treatment Systems RODI Systems Corp., Aztec, New Mexico, USA Summary: This document describes a totally self-contained, containerized wastewater treatment system capable of reducing BOD levels of domestic and industrial wastewater. By utilizing containerized construction and a submerged membrane treatment technique, RODI Systems can provide a completely assembled, pre-tested system capable of treating wastewater from a number of sources. The MBR system can be mated with one of RODI’s containerized RO systems to further reduce dissolved solids concentration in the treated wastewater effluent. RODI’s containerized water treatment systems offer a number of advantages including ease of financing, ease of installation, flexibility, and cost effectiveness.

INTRODUCTION

CMBR TREATMENT PROCESS

For the last fifteen years, the professionals at RODI Systems Corp. have been involved in the design and construction of membrane-based water treatment systems. RODI has built its reputation around treatment of challenging feed waters such as oil field produced water, seawater, and contaminated brackish groundwater. The majority of the treatment systems designed and built by RODI have been portable, either trailer-mounted or built inside a general purpose, dry cargo shipping container.

RODI Systems’ CMBR process uses aerobic digestion as does a conventional system. However, with the CMBR process, a submerged membrane module is used to separate the treated wastewater from the biomass in the bioreactor. Use of the membrane offers several advantages:

This paper describes a containerized membrane bioreactor treatment system (CMBR) designed by RODI to treat domestic or industrial wastewater. This system was designed in multiple sizes to fit a 20 ft or 40 ft shipping container (plus external bioreactor) and provide a production rate of 5,000 to 50,000 gallons per day.

CONVENTIONAL TREATMENT PROCESS The most common biological process for the treatment of wastewater is the activated sludge process (Figure 1). The equipment used for this process consists of two main compartments, the aeration tank (or bioreactor) and the clarifier. Wastewater enters the bioreactor where it is aerated and the organic material in the wastewater is digested, or converted, by the micro-organisms in the sludge. The clarifier separates the sludge from the treated wastewater by allowing the sludge to settle. A portion of the settled sludge is purged and the remainder is recycled to the bioreactor. In conventional systems, the bioreactor needs to be large since the biomass concentration is maintained at 3 to 5 grams per liter to enable good solids separation in the clarifier.

Smaller Bioreactor - Membrane separation of liquid and solids allows the biomass in the bioreactor to be as high as 25 grams per liter. This results in a bioreactor a fraction of the size as that necessary in a conventional system of the same throughput. Longer Sludge Retention - Longer sludge retention times in a membrane bioreactor mean easier sludge handling and less sludge to be disposed of. Membrane bioreactors are less sensitive to changes in wastewater quality. Superior Effluent Quality - Since the treated wastewater passes through a membrane, the quality of the effluent is superior and virtually devoid of any suspended solids. Effluent from a membrane bioreactor may be fed directly to a reverse osmosis unit with no additional treatment. In addition to the advantages listed above, the CMBR units from RODI Systems offer additional benefits. SMALL FOOTPRINT AND PORTABILITY - The CMBR unit consists of a standard intermodal container housing the bioreactor, blowers, recirculation pump, membrane modules, and controls. This results in a compact system that requires a minimum of site preparation and a shorter installation time. SELF-CONTAINED OPERATION. The CMBR is designed to operate as a portable, self-contained treatment system. All necessary treatment equipment and supplies are furnished as part of the container housing the treatment system.

EASE OF MAINTENANCE. The CMBR utilizes submerged flat-plate membrane modules which are continuously air-scoured to reduce fouling. Specialized control sequences allow “relax” intervals which further protects the membrane from flux loss due to particulate fouling. When operated properly, the CMBR membrane modules will provide superior flux rates for extended periods with no maintenance necessary. AUTOMATIC CONTROL. The CMBR is equipped with a microprocessor-based monitoring and control system. This system may be remotely monitored via telephone modem. The automatic control system is equipped with manual overrides should manual control become necessary. ECONOMIC OPERATION. While membrane bioreactors tend to be more energy intensive to operate vs. conventional plants, the CMBR is designed to be as energy efficient as possible. Variable frequency drives are used on the blower motors to allow operation at maximum energy efficiency. Automatic controls minimize labor costs.

TREATMENT SYSTEM SPECIFICATIONS Specifications for RODI’s CMBR are listed below: Bioreactor - The bioreactor is comprised of rectangular polypropylene or steel tanks. On smaller systems, the bioreactor is mounted inside the container. On larger systems, the bioreactor is skid-mounted and is designed to be located next to the membrane module container. The bioreactor is furnished with all of the necessary piping connections. Container - The blowers, filtrate pump, recirculation pumps, instrumentation, and control system are housed in a modified dry cargo shipping container. Modifications include waterproof flooring, insulation on ceiling and walls, one man door for personnel access, overhead lighting and power outlets, and air conditioning and heating (if necessary).

Membrane Modules - The CMBR utilizes submerged flat-plate membrane modules. These modules are constructed on an advanced polymeric material and are capable of rejecting suspended solids greater than 0.01 to 0.1 microns in size. This results in a superior effluent quality with less than 5 mg/l BOD and less than 1 mg/l total suspended solids. Electrical - The electrical system meets NEC and UL requirements and includes a main fused disconnect with a secondary circuit breaker. All branch circuits are also protected with secondary circuit breakers or fuses. Monitoring and Control System - The CMBR is equipped with a computerized control system with an LCD touch screen operator interface. Manual overrides are available for all control functions. All necessary operating data is monitored and logged. Data is available for local download or remote troubleshooting via telephone, cellular, or satellite modem. Options - The following options may also be provided as part of the CMBR package: • • • • •

Equalization tank; Grit removal and screen separation equipment; Anoxic reactor for denitrification; Sludge handling equipment Effluent disinfection.

Size and Weight - See Table 1. Production Capacity - See Table 1.

FLOW DIAGRAM The overall flow diagram for the basic CMBR is illustrated in Figure 2.

FIGURE 1. CONVENTIONAL TREATMENT SYSTEM FLOW DIAGRAM

Wastewater Effluent Clarifier Aeration Tank

Blower Air Sludge Transfer Pump Surplus Sludge Waste Sludge

FIGURE 2. BASIC CMBR FLOW DIAGRAM

HOCl Injection, Ozone, or UV (Optional)

Vent

Submerged Membrane Modules Bioreactor

Filtrate Pump

Wastewater

Effluent

Air Diffuser

Air Diffuser

Waste Sludge Blower Air

TABLE 1. CMBR CAPACITY, SIZE, AND WEIGHT1 Nominal Treatment Capacity (at 350 mg/l BOD)

5,000 GPD

Elevation View Container Size (L x W x H)

Plan View

20 ft x 8 ft x 9 ft 9.0'

Approximate Container Weight

10,000 lbs

Bioreactor Size (L x W x H)

Inside Container

Nominal Treatment Capacity (at 350 mg/l BOD)

10,000 GPD

8.0'

20.0'

20.0'

9.0'

Elevation View Container Size (L x W x H)

40 ft x 8 ft x 9 ft

Approximate Container Weight

20,000 lbs

40.0'

8.0'

Plan View Bioreactor Size (L x W x H)

1

Inside Container

For Evaluation Only. Do Not Use for Construction.

40.0'

Nominal Treatment Capacity (at 350 mg/l BOD)

25,000 GPD 8.5'

Elevation View Container Size (L x W x H)

40 ft x 8 ft x 8.5 ft

Approximate Container Weight

22,000 lbs

40.0'

18.0'

Plan View

Bioreactor Size (L x W x H)

40 ft x 8 ft x 8.5 ft 40.0'

Nominal Treatment Capacity (at 350 mg/l BOD)

50,000 GPD 9.0'

Elevation View Container Size (L x W x H)

40 ft x 8 ft x 8.5 ft

Approximate Container Weight

23,000 lbs

40.0'

28.0'

Plan View

Bioreactor Size (D x H)

40 ft x 8 ft x 8.5 ft 40.0'

v. 100308

505-334-5865 ph 505-334-5867 fax www.rodisystems.com email: [email protected] 936 Highway 516 Aztec, NM 87410