Micro water

EFFECTIVE WASTEWATER TREATMENT MUST

EFFECTIVE WASTEWATER TREATMENT MUST

• ELIMINATE PATHOGENS, REMOVE PATHOGEN

• PREVENT SPREAD OF DISEASE VIA WATER OF RIVERS, LAKES

• PREVENT SHELLFISH CONCENTRATING MICROBES

• DECREASE LEVEL OF ORGANIC COMPOUNDS, POLLUTANTS

• HIGH NUTRIENT CONTENT IN SEWAGE NEEDS TO BE REMOVED

• NUTRIENTS LEAD TO RAPID GROWTH OF MICROBES

• AEROBES CONSUME AND DEPLETE O2

• FISH, OTHER AQUATIC ANIMALS DIE FOR LACK OF O2

Biochemical oxygen demand (BOD)

• amount of o2 required for microbial decomposition of organic matter in a sample

  • High BOD values indicate large amounts are present

  • BOD of raw sewage is about 300-400 mg/liter

  • Easily depletes the ~5-10 mg/liter dissolved o2 in fresh water

• Determined in a bioassay

  • Well-aerated microbe-containing water sample

  • Incubated under standard conditions in dark

  • o2 levels measured before and after, difference reflects the BOD of the sample

Municipal wastewater treatment methods

• 1972 federal water pollution control act (clan water act) Mandates primary and secondary treatment

  • Once treated, effluent (liquid portion) is discharged

  • Sludge (solid portion) additionally treated

Primary treatment

• Physical process to remove materials, filtered of settle out

  • Raw sewage is screened to remove large objects

  • Removes 50% of solids and ~25% of BOD

  • Skimmers remove scum, other floating material, grease, oil

  • Sewage sits in sedimentation tank, solids settle out

    • Sludge is then removed

  • Wastewater is sent for secondary treatment

Secondary treatment

• Biological process that converts suspended solids to inorganic compounds and cell mass for removal

  • Eliminates as much as 95% of BOD

• Microbial growth actively encouraged

  • Aerobes oxidize actively encouraged

  • Microbial populations could be killed if too much toxic industrial waster or household material added

• Methods used include:

  • Activated sludge process

  • Trickling filter (FTF) system

  • Lagoons

  • Constructed wetlands

Activated sludge process

MIXED POPULATIONS OF AEROBES GROW AS FLOCS

(BIOFILMS)

• BACTERIA, ARCHAEA, FUNGI, AND PROTISTS

• A SMALL PORTION OF LEFTOVER SLUDGE FROM PREVIOUS

LOAD IS INTRODUCED

• PLENTY OF O2 ADDED BY MIXING WASTEWATER IN AERATOR

• ORGANIC MATTER IS CONVERTED TO BIOMASS, WASTE

PRODUCTS

• WASTEWATER SENT TO SEDIMENTATION TANK; FLOCS SETTLE

• SLUDGE IS REMOVED

• COMPLICATION IS BULKING, CAUSED BY FILAMENTOUS

BACTERIA THAT PREVENT FLOCS FROM SETTLING

Trickling filter system

• USED IN SMALLER WASTEWATER TREATMENT PLANTS

• ROTATING ARM SPREADS EFFLUENT OVER BED OF

PLASTIC PIECES OR COURSE GRAVEL AND ROCKS

• SURFACES COATED WITH BIOFILM THAT DEGRADES

PASSING ORGANIC MATERIAL

• BIOFILM CONTAINS BACTERIA, FUNGI, ALGAE, PROTOZOA, &

NEMATODES

• RATE OF FLOW ADJUSTED FOR MAXIMUM

DEGRADATION

Secondary treatment methods

• Lagoons

  • Wastewater remains in shallow ponds (days to weeks)

  • Algae, Cyanobacteria grow at surface, provide o2 that allows aerobic organisms to degrade organic materials

• Constructed wetlands

  • Same principle, but designed as suitable wildlife habitat

What is advanced treatment?

• ANY PURIFICATION BEYOND SECONDARY TREATMENT

• MAY INVOLVE PHYSICAL, CHEMICAL, OR BIOLOGICAL PROCESSES

• USUALLY EXPENSIVE AND NOT COMMON IN THE PAST

• OFTEN DESIGNED TO REMOVE COMPOUNDS THAT FOSTER THE GROWTH OF

ALGAE, CYANOBACTERIA; ACCUMULATIONS CREATE SURFACE SCUM, INCREASE

BOD

• AMMONIA REMOVED BY AMMONIA STRIPPING

• NITRATES REMOVED BY DENITRIFYING BACTERIA

• ANAMMOX BACTERIA USE AMMONIA FOR ENERGY AND NITRITE AS A

TERMINAL ELECTRON ACCEPTOR

Biol 316 24

• PHOSPHATES ELIMINATED VIA CHEMICAL PRECIPITATION

Types of advanced treatment:

• Disinfection

  • Chlorine, ozone, or uv light used to decrease numbers of microorganisms

  • Water can be dechlorinated to avoid excessive release

• Anaerobic digestion

  • SLUDGE FROM SEDIMENTATION STEPS IS DIGESTED ANAEROBICALLY

    • VARIOUS MICROBES ACT SEQUENTIALLY

    • ORGANIC COMPOUNDS à ORGANIC ACIDS, CO2, H2

    • ORGANIC ACIDS à ACETATE, CO2, H2

    • ACETATE, CO2, H2 à METHANE (CH4)

    • WATER IS REMOVED, YIELDS NUTRIENT-RICH STABILIZED SLUDGE

    • CAN BE INCINERATED, LANDFILLED, OR USED TO IMPROVE SOILS

    • CONCERNS ABOUT HEAVY METALS, OTHER POLLUTANTS

Septic systems - in rural areas

SOLID MATERIAL SETTLES, IS DEGRADED

ANAEROBICALLY IN TANK

• EFFLUENT, WITH HIGH BOD, PERCOLATES

THROUGH DRAIN FIELD

• AEROBIC MICROBES OXIDIZE ORGANIC MATERIAL

• SYSTEMS MUST BE PROPERLY DESIGNED, MONITORED

Drinking water treatment and testing

• POTABLE WATER – SAFE TO DRINK

• LARGE CITIES TYPICALLY OBTAIN FROM SURFACE WATERS

• LAKES AND RIVERS, WHICH MAY RECEIVE WASTEWATER

• SMALLER COMMUNITIES OFTEN USE GROUNDWATER

• PUMPED FROM A WELL FROM AN AQUIFER

• LAYERS OF ROCK, SAND, GRAVEL CONTAINING WATER

• SOMEWHAT PROTECTED, BUT STILL AT RISK OF CONTAMINATION

• SAFE DRINKING WATER ACT OF 1974 REGULATES IN U.S.

• AMENDED IN 1986 AND 1996; GIVES EPA AUTHORITY

• EPA SETS STANDARDS TO CONTROL CONTAMINANTS

Water treatment processes

• DESIGNED TO ELIMINATE PATHOGENIC MICROBES, CHEMICALS

• SETTLING

  • WATER FLOWS INTO RESERVOIRS, PARTICULATE MATTER SETTLES

• COAGULATION

  • WATER TRANSFERRED TO TANK,

  • MIXED WITH ALUM THAT CAUSES COAGULATION OF SUSPENDED MATERIAL

• SEDIMENTATION - MIXTURE THEN FLOWS TO TANK

  • FLOCS SINK, SOME MICROBES, OTHER MATERIALS TRAPPED

• FILTRATION

  • WATER IS FILTERED TO REMOVE MICROBES INCLUDING BACTERIA, PROTOZOAN CYSTS, OOCYSTS

  • OFTEN THROUGH A THICK BED OF SAND AND GRAVEL

  • BIOFILMS ON FILTERS USE NUTIRNTS FROM PASSING WATER, RESULTS IN LESS MICROBIAL GROWTH IN DELIVERY PIPES

• ORGANIC CHEMICALS CAN BE REMOVED BY ACTIVATED CHARCOAL FILTRATION

More water treatment processes

FINALLY, WATER TREATED WITH CHLORINE OR

OTHER DISINFECTANTS

• KILLS ANY HARMFUL VIRUSES, BACTERIA, PROTOZOA

• DISINFECTION BY-PRODUCTS OF CHLORINE MAY BE

CARCINOGENIC

• UV, OZONE INCREASINGLY USED AS ALTERNATIVES

• SMALL AMOUNT OF CHLORINE STILL ADDED TO

PREVENT CONTAMINATION

• ORGANIC COMPOUNDS CONSUME FREE-CHLORINE;

MORE NEEDED IN WATERS WITH HIGH

CONCENTRATIONS

Water testing

• PRIMARY CONCERN IS POSSIBILITY OF CONTAMINATION WITH ANY OF A WIDE

RANGE OF INTESTINAL PATHOGENS

• INDICATOR ORGANISMS ARE TESTED AS NOT FEASIBLE TO TEST ALL

• TEST FOR MICROBES ROUTINELY FOUND IN FECES, SURVIVE LONGER THAN INTESTINAL PATHOGENS, AND ARE EASY TO DETECT

• TOTAL COLIFORMS COMMONLY USED IN U.S. AS INDICATOR

• MEMBERS OF FAMILY ENTEROBACTERIACEAE

  • FACULTATIVE ANAEROBES,

  • GRAM-NEGATIVE, ROD-SHAPED, NON-SPORE-FORMING

  • FERMENT LACTOSE, FORMING ACID AND GAS WITHIN 48 HOURS AT 35°C

• FECAL COLIFORMS MORE LIKELY TO BE OF INTESTINAL ORIGIN

• E. COLI IS MOST COMMON

Methods of water testing

METHODS TO DETECT TOTAL COLIFORMS IN WATER SAMPLES

• MOST PROBABLE NUMBER (MPN) METHOD: STATISTICAL ASSAY OF CELLS USES

SUCCESSIVE DILUTIONS TO DETERMINE

• RESULTS = PRESENCE/ABSENCE TEST

• POSITIVE TUBES FURTHER TESTED TO CONFIRM

• MEMBRANE FILTRATION: SAMPLE PASSED THROUGH FILTER

• FILTER PLACED ON LACTOSE-CONTAINING SELECTIVE AND DIFFERENTIAL AGAR

MEDIUM

• REVISED TOTAL COLIFORM RULE ESTABLISHES MAXIMUM NUMBER ALLOWED

• LIMIT DEPENDS ON HOW MANY SAMPLES ROUTINELY COLLECTED, MONITORING AND

CORRECTIVE ACTIONS IF REQUIRED

• VIOLATIONS MUST BE REPORTED TO STATE AND PUBLIC

Sanitary landfills for solid waste disposal

• WIDELY USED FOR NON-HAZARDOUS WASTE DISPOSAL

• MINIMIZE DAMAGE TO HUMAN HEALTH, ENVIRONMENT

• LANDFILLS MUST BE LOCATED AWAY FROM

• WETLANDS,

• EARTHQUAKE-PRONE FAULTS,

• FLOOD PLAINS, ETC.

• SITE IS LINED WITH PLASTIC MEMBRANE ON TOP OF THICK LAYER OF CLAY

• LAYER OF SAND WITH DRAINAGE PIPES PLACED ON TOP OF THIS

• WASTES ARE ADDED, COMPACTED, AND COVERED WITH SOIL

• ONCE FULL, LANDFILL IS COVERED WITH SOIL AND PLANTS

• CAN BE USED FOR RECREATION, ULTIMATELY CONSTRUCTION SITE

• METHANE, GASES VENTED; METHANE BURNED OR RECOVERED

Disadvantages of sanitary landfills

SITES NEAR URBAN, SUBURBAN AREAS ARE LIMITED

• METHANE GAS MUST BE REMOVED - CAN TAKE MORE THAN 50 YEARS

• GAS EXPLOSIONS CAN OCCUR IF BUILDINGS ARE CONSTRUCTED BEFORE METHANE IS

REMOVED

• POLLUTANTS CAN LEAK INTO UNDERGROUND AQUIFERS

• SANITARY LANDFILLS TRADITIONALLY LOW-COST;

• INCREASED COST AND DECREASED LAND AVAILABILITY IS DRIVING INTEREST IN

ALTERNATIVES

• SOME CITIES CHARGE BASED ON SIZE OF CONTAINER COLLECTED

• RECYCLING PROGRAMS REDUCE VOLUME GOING TO LAND FILLS