Waste disposal and

decomposition

Landfills: problems with cost, availability, ground-water pollution, liquid content, methane production.

Oceans: the “Victoria” solution, Seattle’s Lake Washington and

Puget Sound experience.

Incineration; problems with location, NIMBY, Not In My BackYard

Options for sewage disposal

In the 1950’s demonstration by Professor Tommy Edmondson that the Lake Washington ecosystem had been substantially changed due to discharge of effluent. Nitrogen pollution

In 1958 voters in Seattle and King County created Metro, an agency charged with creating a regional wastewater treatment system.  

In 1966 construction of a primary treatment plant completed at West Point with discharge into Puget Sound.

1972 Federal Clean Water Act

In 1972 first biosolids applications at Pack Forest

In 1991 Metro begins an expansion of the plant West Point plant

Some developments leading to recycling

Quantities and collection

Biology and engineering of treatment

Recycling through biosolids application

RecyclingThe principle is: (1) to use a treatment plant to remove soluble nitrogen from the effluent and kill pathogens, and (2) to apply the solid processed from bacterial matter to agricultural fields, forests, and land requiring re-medial treatment

There are problems associated with:

Total Suspended Solids loading (average annual) 181,000 lbs/day

Electricity generated 7,437,972 kilowatt hours

Biosolids produced 53,409 wet tons; 13,277 dry tons per year

Reclaimed water used 0.61 mgd

Outfall 3,600 ft. offshore; 240 ft. deep; 500 ft. diffuser

Annual budget for King County: Operating, $82 million; Capital, $96 million

At the West Point plant:

In King County 95% of the wastewater is from homes and businesses, with only 5% from industries

Quantities and Collection

Two waste water treatment plants in King County

Average daily capacity of the West plant is 133 million gallons per day

Biology and engineering of treatment

Most organic matter is converted by micro–organisms to inorganic forms. This process is called mineralization.

Large molecules will first be broken down to smaller ones by bacterial exo-enzymes, enzymes that bacteria excrete.

The most important organisms involved in these conversions are heterotrophic bacteria.

It is extremely difficult to identify bacterial genera, let alone species, from water purification systems, but it is obvious that the genera Flavobacterium and Pseudomonas are important.

Overview of treatment

O2 + bacteria + dissolved and suspended organic matter

Screen

Gritchamber

Secondary treatment

Primary treatment Skim

and settle solids

Solids processing

Blend

ThickenHeat

Methane

Anaerobic bacterial digestion

Centrifuge

Chlorination

Puget Sound

Settled biomass

High Purity Oxygen activated sludge process

West Point Treatment Plant

Nitrogen removal into biomass

Nitrogen metabo;ism

mean cellresidence times

Nitrogen is incorporated into microbial biomass. Two types of bacteria process ammonium to nitrate

http://bark214-3.berkeley.edu/MCB290/illana.htm

Anaerobic sludge digester

http://bark214-3.berkeley.edu/MCB290/illana.htm

Anaerobic methane production

Electricity sold to Seattle City Light

30% of power for the plant

We do not know the precise composition of bacteria in either the aerobic or anaerobic processes.

Plating out and culturing provides micro-organisms with a very different environment than found in the tanks

There is some hope to use new DNA/RNA identification techniques to identify bacteria and seek ways of improving processing rates

Problems!

Increased treatment capacity will be needed

What will happen in the future? A third plant will be added.

But there is resistance to expanding the processing area of existing plants although their current capacity may be exceeded

350 feet deep processor

A 350 feet deep processor is being investigated!!

Temp and O2 control systems

Recycling through biosolids application

What we do not have!

Some regulations

Seattle Biosolids Applications

The “Cornell” recommendations

What we do not have!

What we need to avoid

Giardia lamblia trophozoites, as they appear with the scanning electron microscope.  Original image by Arturo Gonzalez, CINVESTAV, Mexico.

http://www.biosci.ohio-state.edu/~parasite/giardia_sem.html

The EPA breaks down land application of biosolids into 4 categories: Agricultural lands, Forest lands, Reclamation sites, and Public contact/Home lawns & gardens.  Each land application category has its own set of requirements according to WAC 173-308-210, 220, 230, 240, and 250.  Washington state has adapted the federal EPA rule 40 CFR 503 standards to its own rule, Chapter 173-308 WAC. 

A Plain English Guide to theEPA Part 503 Biosolids Rule

http://www.epa.gov/owm/bio/503pe/

Some regulations

Class A biosolids contain no detectible levels of pathogens and and meet strict vector attraction reduction requirements and have low levels of metals. Permits are required to ensure that these standards have been met.

Different rules for different classes of biosolids.

Class B biosolids are treated but still contain detectible levels of pathogens. There are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids.

Class A production processes include irradiation, composting, heat drying, heat treatment, pasteurization, thermophilic aerobic digestion, and alkaline stabilization. Class A biosolids do not contain pathogens in sufficient quantity to warrant restricted access or special precautions and may be applied the same way as commercial fertilizer.

Class A Biosolids

Biosolids must be subject to one of the following four (4) time-temperature regimes: 7 percent solid or greater biosolids must be heated to 50 degrees Celsius of higher for 20 minutes or longer. 7 percent solid or greater biosolids in the form of small particles

and heated by contact with either warmed gases or immiscible liquid must be heated to 50 degrees Celsius or higher for 15 seconds or longer. Biosolids less than 7 percent solid must be heated for at least 15

seconds but less than 30 minutes using the following equation:

D=131,700,000/100.14 t Biosolids less than 7 percent solid must be heated to 50 degrees

Celsius of higher with at least 30 minutes of longer contact time.

Alternative 1: Thermally treated biosolids

There are chemical alternatives for application of alkaline

K-S Nara Paddle Dryer/Cooler

King County biosolids are anaerobically digested at the treatment plant to meet Class B pathogen reduction. Further reduction does take place after application in what King County (and other processors) refer to as a hostile environment for microbes

Class B Biosolids

In practice odor is a principal restriction to the location where Class B biosolids can be applied. This can be reduced by chemicals

Restricted Activity Site Restriction

Harvest of food crop touching ground 14 months after applicationHarvest of root crop (see next condition) 20 months after applicationHarvest of root crop if sludge on surface 38 months after applicationHarvest of other food, feed, and fiber crops 30 days after applicationGrazing of animals 30 days after applicationHarvest of turf for high contact site, 1 year after application e.g., golf course or lawn; or public access to turfAccess to sites with high potential for Restrict for 1 yearpublic exposureAccess to sites with low potential for Restrict for 30 days public exposure

EPA Class B biosolids site restrictions

Total Solids 24.8%Ammonia Nitrogen 1.2%Organic Nitrogen 5.5%Phosphorus 1.9%Potassium 0.3%Sulfur 1.1%

Biosolids Quality from the West Point Plant 2000 Average

By weight

Organic nitrogen provides a sustained release of N

West Point Plant National and State Regulatory Standards mg/kg mg/kg

Arsenic 7.07 541Cadmium 3.7 39Copper 529 1500Lead 141 300Mercury 2.71 17Molybdenum 11.1 under reconsiderationNickel 35.1 420Selenium 5.97 36Zinc 804 2800

Trace metals in West Point biosolids

Improved moisture retention

Increased growth – sometimes too much N

“Dryland” soils program

Forest Application

Reclamation

Rapid establishment of vegetation

Issues – returning to ‘natural’ vegetation may be retarded by high N

Bunker Hill Wetland, Idaho

Four arguments against biosolids application

1. Odor and ‘unpleasantness’

2. EPA is not doing its job to ensure compliance with its own regulations

3. Treatment and disposal should be local

4. Class B biosolids can cause illness to people applying them

--Limiting applications to keep soil metals low;--Testing soils before application;--Applying only at agronomic rates;--Supplying all landowners with biosolids quality

information;--Monitoring downstream water bodies and wells;--Calibrating application equipment;--Maintaining setbacks and buffers;--Avoiding application to areas prone to runoff;--Imposing access restrictions for the public.

In practice most of these items are specified in Washington State and EPA regulations

Cornell University site management recommendations

According to EPA estimates for 1993, approximately 33% of the 5.4 million dry metric tons of biosolids generated annually in the US is land applied

This is increasing due to rising costs and less available space in landfills, regulations banning ocean dumping, and a move away from incineration. 

There is likely to be continued discussion as new regions consider biosolids application

Conclusion

So application to the land will increase and must be placed on a sustainable basis

ESC518, formerly MicrobialDegradation, to Bioremediation Science

Courses that deal with this topic

CIVE 484 On-Site Wastewater DisposalCIVE 482 Water and Wastewater Treatment