Tertiary Treatment, Effluent Reuse & Advanced Treatment

Tertiary and advanced wastewater treatment provide additional treatment beyond conventional primary and secondary processes. These processes are used when a facility must achieve higher effluent quality, remove specific pollutants, support water reuse, or meet other treatment objectives.

Operators should understand that advanced treatment does not replace good primary and secondary treatment. Most tertiary processes perform best when upstream treatment is stable and produces consistent water quality.

What Tertiary Treatment Means

Tertiary treatment generally refers to treatment applied after secondary treatment to further improve effluent quality.

Tertiary treatment can target:

• suspended solids;
• nutrients;
• microorganisms;
• dissolved contaminants;
• other constituents that remain after secondary treatment.

Advanced Treatment

Advanced treatment is a broad term for processes designed to achieve treatment beyond conventional secondary treatment or to remove contaminants requiring specialized technology.

Examples can include:

• tertiary filtration;
• membrane treatment;
• advanced nutrient removal;
• activated carbon;
• advanced oxidation;
• specialized disinfection.

Why Additional Treatment Is Used

Additional treatment may be required to:

• meet stringent discharge requirements;
• reduce nutrient loading;
• prepare water for reuse;
• protect sensitive receiving waters;
• remove specific contaminants;
• improve disinfection performance.

Tertiary Filtration

Tertiary filtration removes suspended material remaining after secondary clarification.

Common treatment approaches can include:

• granular-media filters;
• cloth or disk filtration;
• membrane filtration;
• other solids-polishing systems.

Why Tertiary Filtration Helps

Reducing suspended solids can improve:

• final effluent clarity;
• disinfection performance;
• downstream reuse treatment;
• overall effluent quality.

Filter Loading

A simplified filtration-rate relationship is:

Filtration Rate = Flow ÷ Filter Area

Filtration-Rate Example

A tertiary filter receives 800 gpm and has 400 ft² of surface area.

Filtration Rate = 800 ÷ 400

Filtration Rate = 2.0 gpm/ft²

The acceptable operating rate depends on the specific filter design.

Head Loss

As solids accumulate in a filter, resistance to flow can increase.

Operators should monitor:

• head loss;
• effluent turbidity;
• filter run length;
• backwash frequency.

Backwashing

Many tertiary filters require periodic cleaning or backwashing.

Poor backwashing can lead to:

• shorter filter runs;
• solids accumulation;
• higher head loss;
• poor effluent quality.

Upstream Solids Affect Tertiary Filters

If secondary clarifiers carry excessive solids into tertiary filters, the filters may foul rapidly.

The correct response may require improving secondary clarification rather than simply increasing backwash frequency.

Nutrient Removal

Advanced wastewater treatment may include additional nitrogen or phosphorus removal.

Nitrogen removal can involve:

• nitrification;
• denitrification;
• other specialized processes.

Phosphorus removal can involve:

• biological phosphorus removal;
• chemical precipitation;
• filtration;
• combinations of processes.

Nitrification

Nitrification biologically converts ammonia to more oxidized nitrogen forms.

Important operating factors include:

• dissolved oxygen;
• temperature;
• pH;
• alkalinity;
• sludge age;
• toxic conditions.

Denitrification

Denitrification converts nitrate to nitrogen gas under suitable biological conditions.

The process generally requires:

• nitrate;
• an available carbon source;
• low dissolved oxygen conditions appropriate for the process;
• adequate contact time.

Phosphorus Precipitation

Chemicals can be added to convert dissolved phosphorus into solids that can be separated from the water.

Operators should monitor:

• chemical dose;
• mixing;
• pH;
• solids production;
• filtration or clarification performance.

Chemical Feed Calculation

A common relationship is:

Chemical Feed, lb/day = Flow, MGD × Dose, mg/L × 8.34

Chemical Feed Example

A facility treats 4.0 MGD and applies a treatment chemical at 5 mg/L.

Chemical Feed = 4.0 × 5 × 8.34

Chemical Feed = 166.8 lb/day

Membrane Treatment

Membrane processes use selective barriers to separate contaminants from water.

Depending on membrane type and treatment objectives, membranes can remove:

• suspended particles;
• microorganisms;
• some dissolved substances;
• salts and other dissolved constituents in higher-pressure processes.

Membrane Fouling

Fouling occurs when material accumulates on or within membrane surfaces.

Possible foulants include:

• suspended solids;
• organic matter;
• scale;
• biological growth.

Membrane Monitoring

Operators can monitor:

• feed pressure;
• transmembrane pressure where applicable;
• product flow;
• recovery;
• water quality;
• cleaning frequency.

Membrane Recovery

A simplified relationship is:

Recovery, % = Product Flow ÷ Feed Flow × 100

Recovery Example

A membrane system receives 2.0 MGD and produces 1.5 MGD of product water.

Recovery = 1.5 ÷ 2.0 × 100

Recovery = 75%

Residual Streams

Advanced treatment can produce residual streams such as:

• filter backwash water;
• membrane concentrate;
• spent media;
• chemical sludge;
• cleaning waste.

Operators should understand where these residuals go and how they affect other plant processes.

Activated Carbon

Activated carbon can remove selected dissolved organic compounds through adsorption.

Wastewater applications can include polishing for:

• specific organic compounds;
• odor-producing compounds;
• other treatment objectives.

Adsorption Capacity

Activated carbon has finite adsorption capacity.

As capacity is used, contaminant breakthrough can occur.

Advanced Oxidation

Advanced oxidation processes generate highly reactive chemical species that can destroy certain difficult organic compounds.

Systems may use combinations of:

• oxidants;
• ultraviolet energy;
• other process conditions.

Disinfection

High-quality effluent or reclaimed water commonly requires effective disinfection.

Disinfection technologies can include:

• chlorine;
• ultraviolet light;
• ozone;
• other approved technologies.

Suspended Solids Can Affect Disinfection

Particles can interfere with disinfection by shielding microorganisms or increasing disinfectant demand.

Improved solids removal can therefore improve disinfection performance.

UV Treatment

UV performance depends on factors such as:

• UV intensity;
• water clarity;
• lamp condition;
• flow;
• reactor condition.

Chlorine Treatment

When chlorine is used, operators should understand:

• dose;
• demand;
• residual;
• contact time;
• dechlorination where required.

Water Reuse

Water reuse, also called water recycling or water reclamation, means treating wastewater or another used water source so the water can be used again for a beneficial purpose.

Reuse applications can vary widely and can include:

• landscape irrigation;
• industrial uses;
• environmental applications;
• groundwater recharge;
• other nonpotable uses;
• potable reuse systems with extensive additional treatment.

Treatment Depends on Intended Use

Not every reuse application requires the same water quality.

The required treatment depends on factors such as:

• source water;
• intended use;
• potential human exposure;
• environmental exposure;
• applicable requirements.

Nonpotable Reuse

Nonpotable reuse uses reclaimed water for purposes other than drinking.

Examples can include:

• irrigation;
• industrial cooling;
• process water;
• other approved uses.

Potable Reuse

Potable reuse involves reclaimed water becoming part of a drinking-water supply.

Because potential human exposure is much greater, potable reuse requires extensive treatment, monitoring, and multiple protective barriers.

Multiple Treatment Barriers

Advanced reuse systems can use several processes that provide overlapping protection.

Multiple barriers reduce reliance on any single treatment unit.

Treatment Redundancy

Redundancy means that more than one process may contribute to removing or controlling the same type of contaminant.

Operators should understand which barriers protect against:

• particles;
• microorganisms;
• dissolved contaminants;
• other treatment risks.

Reuse Is Not Simply Effluent Disposal

Reuse changes treated wastewater from a waste stream into a water resource intended for another beneficial use.

This can require additional:

• treatment;
• storage;
• monitoring;
• distribution infrastructure.

Reuse Storage

Storage can help balance differences between water production and reuse demand.

Operators should monitor storage for:

• water age;
• disinfectant conditions;
• algae;
• sediment;
• water-quality changes.

Reuse Distribution

Reclaimed-water distribution systems require appropriate operational controls to maintain water quality and prevent unintended connections or uses.

Specific requirements vary by jurisdiction and intended use.

Monitoring Advanced Treatment

Advanced systems often depend on multiple measurements.

Parameters can include:

• flow;
• turbidity;
• TSS;
• BOD or COD;
• nitrogen;
• phosphorus;
• pressure;
• UV intensity;
• disinfectant residual;
• process-specific contaminant measurements.

Online Instruments

Advanced processes often use continuous or frequent online measurements.

Operators should verify:

• calibration;
• sensor condition;
• sample flow;
• alarm settings;
• data trends.

Alarm Response

An alarm should lead to a defined operational response.

Operators should know:

• what triggered the alarm;
• which treatment barrier is affected;
• whether flow should continue;
• what verification is required.

Process Integrity

Advanced treatment requires reliable equipment and controls.

A process can fail because of:

• mechanical failure;
• instrument failure;
• loss of chemical feed;
• membrane damage;
• poor upstream water quality.

Upstream Treatment Matters

Poor secondary treatment can increase:

• filter loading;
• membrane fouling;
• disinfectant demand;
• UV interference;
• advanced-treatment operating cost.

Example: Tertiary Filter Head Loss Rises Rapidly

Review:

• secondary clarifier effluent TSS;
• filtration rate;
• backwash performance;
• filter-media condition.

Example: Tertiary Effluent Turbidity Increases

Possible causes include:

• filter breakthrough;
• hydraulic overload;
• poor backwashing;
• upstream solids carryover;
• instrument problems.

Example: Membrane Pressure Increases

Possible causes include:

• fouling;
• scaling;
• poor pretreatment;
• blocked equipment;
• changes in feed-water quality.

Example: Membrane Product Flow Declines

Review:

• feed pressure;
• membrane condition;
• temperature;
• fouling;
• cleaning history.

Example: Reuse Demand Falls

If reclaimed-water production continues while demand decreases, storage volume and water age can increase.

Operators should monitor storage and distribution conditions.

Example: UV Intensity Drops

Possible causes include:

• lamp aging;
• lamp failure;
• sleeve fouling;
• sensor fouling;
• water-quality deterioration.

Example: Chlorine Demand Increases

Review:

• effluent organic matter;
• suspended solids;
• ammonia;
• process changes;
• chemical feed.

Example: Phosphorus Removal Declines

Review:

• chemical dose;
• mixing;
• pH;
• solids separation;
• influent phosphorus load.

Example: Nitrogen Removal Declines

Review:

• temperature;
• dissolved oxygen;
• carbon availability;
• pH and alkalinity;
• loading;
• process-zone conditions.

Residuals Management

Operators should account for residuals created by tertiary and advanced treatment.

These can affect:

• solids-handling capacity;
• plant recycle loads;
• disposal requirements;
• chemical use.

Energy Use

Advanced treatment can require substantial energy for:

• high-pressure pumping;
• membrane systems;
• UV equipment;
• ozone generation;
• aeration;
• advanced filtration.

Energy Trends

Increasing energy use at similar treatment flow can indicate:

• fouling;
• higher pressure requirements;
• equipment deterioration;
• poor process efficiency.

Process Records

Useful records can include:

• flow;
• influent and effluent quality;
• filter pressure or head loss;
• membrane pressure;
• chemical feed;
• UV intensity;
• disinfectant residual;
• reuse production;
• reuse demand;
• equipment alarms.

Common Tertiary and Advanced Treatment Mistakes

• Expecting advanced treatment to compensate indefinitely for poor secondary treatment.
• Ignoring upstream solids carryover.
• Operating filters only by elapsed time instead of actual performance.
• Ignoring membrane fouling trends.
• Using percentage removal without reviewing final concentration.
• Failing to account for residual streams.
• Assuming all water reuse applications require the same treatment.
• Ignoring intended end use when evaluating reclaimed-water quality.
• Ignoring alarms or instrumentation drift.
• Evaluating advanced processes independently instead of as multiple treatment barriers.

A Practical Tertiary-Treatment Review

1. Review secondary effluent quality.
2. Review tertiary influent flow.
3. Review filter or membrane loading.
4. Check head loss or pressure.
5. Review treated-water turbidity and solids.
6. Review nutrient performance where applicable.
7. Review disinfection.
8. Review residuals production.
9. Compare performance with historical trends.

A Practical Reuse-System Review

1. Confirm the intended reuse application.
2. Review source-water quality.
3. Review each treatment barrier.
4. Review disinfection.
5. Review storage conditions.
6. Review reclaimed-water distribution conditions.
7. Review process alarms.
8. Review final water-quality measurements.

A Practical Membrane Review

1. Review feed-water quality.
2. Review pretreatment performance.
3. Review feed pressure.
4. Review product flow.
5. Calculate or review recovery.
6. Check fouling indicators.
7. Review cleaning history.
8. Review concentrate flow.

Membrane Filtration Operations and Troubleshooting

Wastewater membrane filtration requires operators to evaluate hydraulic performance, membrane condition, permeate quality, cleaning effectiveness, and the interaction between membrane equipment and upstream treatment processes.

Membrane Filtration and Membrane Bioreactors

Tertiary membrane filtration treats wastewater after upstream treatment steps, commonly providing additional solids removal or effluent polishing. A membrane bioreactor (MBR) combines biological wastewater treatment with membrane separation, generally replacing conventional secondary clarification as the primary solids-separation step.

Membrane processes vary in configuration, pore size, operating pressure, and separation objectives. Operators must distinguish membrane filtration used for particle separation from higher-pressure processes designed to remove dissolved constituents.

Flux and Transmembrane Pressure

Membrane flux is the permeate flow rate divided by the effective membrane area. It describes how much water passes through a given membrane area per unit time.

Flux = Permeate Flow / Membrane Area

Transmembrane pressure (TMP) represents the effective pressure difference driving water through the membrane. Its calculation depends on membrane configuration and the relevant feed, concentrate, and permeate pressures.

Operators should follow manufacturer instructions when calculating or interpreting TMP rather than applying a single pressure formula to every installation.

Permeability and Performance Trends

Hydraulic membrane permeability relates flux to TMP. A simplified expression is:

Permeability = Flux / TMP

Because membrane performance depends on temperature and operating conditions, comparisons should use appropriate normalized data whenever required by the operating procedure.

At approximately constant flux, increasing TMP may indicate increasing hydraulic resistance. At approximately constant TMP, declining flux may indicate deterioration in membrane hydraulic performance.

Neither observation proves that fouling is the only cause. Instrumentation errors, temperature changes, operating restrictions, and equipment malfunctions must also be considered.

Membrane Fouling and Cleaning

Common fouling mechanisms include accumulation of suspended solids, organic deposits, biological growth, and inorganic scaling.

Operators may evaluate fouling by reviewing TMP, normalized permeability, flow, cleaning frequency, membrane loading, and applicable upstream process data.

Corrective actions depend on the facility design and may include approved backwashing, relaxation, air scouring, chemical cleaning, or changes to upstream operating conditions.

Chemical selection, concentrations, contact times, and cleaning sequences must follow approved procedures and membrane manufacturer requirements. An inappropriate cleaning method can damage membranes or create chemical safety hazards.

Membrane Integrity and Effluent Quality

Membrane integrity concerns the ability of a membrane system to maintain its intended physical separation performance.

An integrity problem may result from damaged membrane elements, faulty seals, defective connections, or other failures that allow material to bypass the intended barrier.

Depending on the system, operators may use specified integrity tests, turbidity or particle monitoring, permeate-quality trends, and equipment inspections to investigate suspected failures.

Acceptable results and testing methods depend on the treatment application and applicable requirements.

Operational Troubleshooting

When membrane performance deteriorates, operators should compare current readings with established baseline and normalized operating trends.

• Rising TMP at stable flux: investigate increased resistance, fouling, and operating conditions.
• Declining flux at stable TMP: investigate hydraulic resistance, feed conditions, and system restrictions.
• Unexpected permeate-quality deterioration: investigate membrane integrity, seals, bypass pathways, and instrumentation.
• Frequent cleaning requirements: evaluate upstream solids loading, cleaning effectiveness, and operating strategy.
• Unusual pressure or flow readings: verify instruments and equipment status before changing process settings.

Operators should avoid increasing pressure beyond approved operating limits to compensate for unexplained performance losses.

Example: Increasing TMP

A tertiary membrane unit operates at approximately constant permeate flux, but normalized TMP increases over successive operating periods.

The operator should review fouling trends, feed-water characteristics, cleaning history, equipment condition, and instrumentation before selecting an approved corrective action.

If permeate quality remains acceptable, the pressure trend alone does not establish a membrane integrity failure.

Exam reminder: Distinguish membrane flux, TMP, permeability, fouling, and integrity. Use operating trends and verified measurements to identify probable causes before adjusting or cleaning membrane equipment.

Disc Filters: Operation and Troubleshooting

Disc filters are used in some wastewater tertiary-treatment systems to remove suspended solids from secondary effluent. Rotating disc units may use cloth or other filter media and automatic cleaning mechanisms. Operators must follow the installed equipment design and manufacturer instructions.

Disc Filter Operating Checks

Operators should monitor influent and filtrate quality, flow, water levels, head loss, cleaning frequency, drive operation, and equipment alarms.

Rising head loss or water level difference may indicate media fouling, excessive solids loading, inadequate cleaning, or a mechanical problem.

Inspect Filter Media and Cleaning Equipment

Inspect accessible filter media for tears, damage, excessive deposits, and improper seating under the approved maintenance procedure.

Verify that the automatic cleaning system operates correctly. Depending on the equipment, this may involve backwash pumps, suction assemblies, spray systems, rotating mechanisms, and associated controls.

Before entering guarded areas or performing maintenance, isolate hazardous energy and follow the facility lockout/tagout procedure.

Troubleshoot Disc Filter Performance

If filtrate suspended solids or turbidity increases, investigate media damage, bypassing, poor sealing, unusually high influent solids, and incorrect operating conditions.

If cleaning cycles become more frequent, review upstream clarifier performance, hydraulic loading, media fouling, and cleaning-system effectiveness.

A drive, cleaning, or level-control alarm requires investigation before the filter is returned to normal service.

Rapid Infiltration Basins: Effluent Application and Operation

Rapid infiltration basins are land-based systems that apply treated wastewater to permeable soil so water can infiltrate through the subsurface. Their use depends on site hydrogeology, approved design, environmental protections, and applicable discharge or reuse permits.

Hydraulic Loading and Basin Rotation

Operators should apply effluent at the approved hydraulic loading rate and follow the specified flooding, drying, and resting cycles.

Alternating basin operation may help maintain infiltration capacity and provide time for surface drying and maintenance.

The appropriate loading and resting schedule depends on site conditions and the approved operating plan; it is not a universal fixed interval.

Monitor Infiltration Performance

Observe ponding depth, infiltration or drawdown trends, distribution uniformity, surface condition, and any required groundwater or monitoring-well results.

Persistently increasing ponding or slower infiltration can indicate surface clogging, solids accumulation, hydraulic overloading, or unsuitable operating conditions.

Investigate and Correct Basin Problems

When infiltration performance deteriorates, review effluent suspended solids, hydraulic loading, application history, basin resting periods, and visible surface deposits.

Approved corrective actions may include resting a basin, adjusting loading, improving upstream treatment, or performing authorized surface maintenance.

Do not increase application rates or bypass monitoring requirements to compensate for declining infiltration capacity.

Environmental Protection and Records

Rapid infiltration operation must remain consistent with applicable permit limits, groundwater protections, monitoring requirements, and facility procedures.

Record flow or application volumes, basin operating periods, observed infiltration conditions, maintenance, sampling, and unusual events.

Exam reminder: Disc filters require monitoring of media condition, solids removal, head loss, cleaning and mechanical operation. Rapid infiltration basins require controlled effluent loading, appropriate basin rotation, infiltration monitoring, groundwater protection, and accurate operating records.

Membrane Bioreactor Process Control and Troubleshooting

A membrane bioreactor (MBR) combines biological wastewater treatment with membrane separation. In an activated-sludge MBR, membranes retain suspended solids and biomass while treated water passes through the membrane system. The membranes replace or supplement conventional solids separation, depending on the facility design.

Successful MBR operation requires coordinated control of biological treatment, membrane performance, aeration, sludge wasting, hydraulic loading, and cleaning. An MBR is not simply a tertiary filter added after conventional treatment.

Biological Treatment and Membrane Separation

Microorganisms remove biodegradable pollutants in the biological reactor. Membrane modules provide physical separation of suspended solids from the treated water.

Operators must monitor both biological-process performance and membrane-system condition. Good membrane filtrate clarity does not by itself demonstrate satisfactory removal of dissolved pollutants or nutrients.

Membrane configurations include immersed and external systems. Operating pressures, cleaning arrangements, and hydraulic controls depend on the installed design.

MLSS, SRT, and Sludge Wasting

Mixed liquor suspended solids (MLSS) concentration and solids retention time (SRT) affect biological activity, oxygen demand, sludge production, and membrane operating conditions.

Operators should use MLSS measurements, sludge wasting rates, process observations, and appropriate mass-balance calculations to evaluate solids inventory.

Excessive solids concentration can increase mixed-liquor viscosity, oxygen-transfer demands, and membrane fouling risk. Insufficient biomass or unsuitable SRT can impair treatment performance.

Changing sludge wasting affects the biological process and may change membrane performance. Adjustments should follow approved operating targets and facility procedures.

Membrane Flux and Transmembrane Pressure

Membrane flux is the permeate flow rate divided by the effective membrane area. Operators use flux and transmembrane pressure (TMP) trends to evaluate membrane loading and filtration resistance.

For example, a membrane producing 120 cubic meters of permeate per hour with 4,000 square meters of effective membrane area operates at an average flux of 30 liters per square meter per hour.

Increasing TMP at approximately constant flux may indicate fouling or other increases in filtration resistance. Falling flux at an approximately constant driving pressure may indicate reduced membrane permeability.

Interpret trends together with temperature, mixed-liquor condition, cleaning history, instrumentation accuracy, and the manufacturer-approved operating range.

Aeration and Dissolved Oxygen Control

Biological aeration supplies oxygen for microbial treatment. Some immersed MBR systems also use air scouring to limit solids accumulation on membrane surfaces.

Biological oxygen requirements and membrane-scouring requirements are related but are not always identical. Operators should monitor dissolved oxygen, airflow, blower operation, process performance, and membrane-cleaning effectiveness.

Insufficient biological aeration may impair organic removal or nitrification. Inadequate membrane scouring may accelerate fouling. Excessive aeration can waste energy and may interfere with process objectives.

Nutrient Removal and Process-Zone Coordination

Facilities designed for biological nutrient removal may combine aerobic, anoxic, and anaerobic process zones with membrane separation.

Operators should evaluate dissolved oxygen, internal recycle, influent loading, available carbon, sludge age, and nutrient trends when investigating nitrification, denitrification, or biological phosphorus removal.

The membrane itself does not automatically remove dissolved ammonia, nitrate, or soluble phosphorus. These constituents require suitable biological or other treatment processes.

Membrane Fouling and Cleaning Response

Membrane fouling may result from accumulated solids, biological deposits, organic materials, inorganic scaling, or changes in mixed-liquor characteristics.

Operators should evaluate TMP, flux, permeability, air-scouring performance, filtration and relaxation cycles, and cleaning records.

Backwashing, relaxation, maintenance cleaning, and recovery cleaning may be used where supported by the installed system.

Chemical cleaning must follow manufacturer instructions, approved chemical concentrations, required isolation, and applicable personnel-safety procedures.

Do not respond to rising TMP by increasing suction or pressure beyond equipment limits.

Troubleshoot MBR Process Performance

When treatment performance deteriorates, distinguish biological-process problems from membrane-separation problems.

High effluent ammonia may indicate inadequate nitrification, unsuitable SRT, insufficient oxygen, or inhibition even when membrane filtrate turbidity remains low.

Increasing TMP with acceptable biological treatment results may indicate fouling, excessive membrane loading, ineffective scouring, or cleaning-system problems.

Unexpected solids in the permeate may indicate membrane damage, sealing problems, integrity loss, or bypassing.

Evaluate multiple operating parameters before making adjustments. A membrane alarm should not automatically trigger a change in sludge wasting or chemical feed.

Operational Records and Integrated Optimization

Review and document influent and permeate flow, MLSS, SRT, sludge wasting, dissolved oxygen, nutrient results, flux, TMP, permeability, aeration, energy use, membrane cleaning, and significant alarms.

Use operating trends to balance effluent quality, membrane reliability, biological stability, and energy consumption.

Exam reminder: MBR process control integrates biological treatment and membrane separation. Evaluate MLSS and SRT, membrane flux and TMP, biological and scouring aeration, nutrient-removal performance, membrane fouling, and equipment integrity before selecting corrective actions.

What to Remember for the Exam

• Tertiary treatment provides additional treatment after secondary treatment.
• Advanced treatment targets pollutants or water-quality goals not adequately addressed by conventional treatment alone.
• Tertiary filtration removes suspended solids remaining after secondary clarification.
• Poor secondary clarification can rapidly overload tertiary filters.
• Filtration rate equals flow divided by filter area.
• Advanced nutrient removal can include nitrification, denitrification, biological phosphorus removal, and chemical phosphorus removal.
• Chemical feed in lb/day can be calculated as MGD × mg/L × 8.34.
• Membrane treatment uses selective barriers to remove particles, microorganisms, or dissolved constituents depending on membrane type.
• Membrane fouling can increase pressure and reduce product flow.
• Membrane recovery equals product flow divided by feed flow times 100.
• Advanced treatment produces residual streams that must be managed.
• Activated carbon removes selected dissolved compounds by adsorption.
• Advanced oxidation can destroy selected difficult organic contaminants.
• Good solids removal can improve disinfection performance.
• Water reuse means treating used water so it can be used again for a beneficial purpose.
• Required reuse treatment depends on source water, intended use, exposure, and applicable requirements.
• Nonpotable and potable reuse have different treatment objectives and risks.
• Multiple treatment barriers provide redundancy and reduce dependence on one process.
• Advanced systems depend heavily on reliable monitoring, alarms, maintenance, and instrumentation.
• Good tertiary and advanced treatment begins with stable upstream treatment and ends with verification of final water quality.