BIOLOGICAL WASTEWATER BASICS

Transcription

1 BIOLOGICAL WASTEWATER BASICS

2 PRESENTATION GOALS EXPLAIN DIFFERENT TYPES OF WASTEWATER EXPLAIN THE DIFFERENT BIOLOGICAL SYSTEMS AND HOW THEY FUNCTION. COMPARE AND CONTRAST AEROBIC AND ANAEROBIC SYSTEMS IDENTIFY LARGEST AREAS OF COST IN BIOLOGICAL SYSTEMS.

3 TYPES OF INDUSTRIAL WASTEWATER CANNOT BE TREATED USING BIOLOGICAL SYSTEMS HIGH LEVELS OF METALS INORGANIC SOLIDS CAN BE TREATED BY USING BIOLOGICAL SYSTEMS COD/BOD ORGANIC WASTE NUTRIENTS NITROGEN PHOSPHORUS FATS, OILS AND GREASE (FOG)

4 BIOLOGICAL TREATMENT UNIT PROCESSES RETURN SOLIDS WASTE SOLIDS PRIMARY TREATMENT EQUALIZATION AEROBIC OR ANAEROBIC TREATMENT BASIN SOLIDS LIQUID SEPARATION SLUDGE TANK EFFLUENT DEWATERING DISPOSAL

5 ADVANCED BIOLOGICAL TREATMENT UNIT PROCESSES RETURN SOLIDS WASTE SOLIDS NORMAL STRENGTH WASTE SELECTOR P REMOVAL AEROBIC TREATMENT SOLIDS LIQUID SEPARATION SLUDGE TANK DIVERSION RETURN SOLIDS SOLIDS-LIQUID SEPARATION EFFLUENT DEWATERING HIGH STRENGTH WASTE ANAEROBIC TREATMENT WASTE SOLIDS DISPOSAL

6 PRIMARY TREATMENT GOALS OF PROCESS PREPARE WASTE TO BE TREATED BY BIOLOGICAL PROCESS UNIT PROCESSES LARGE SOLIDS REMOVAL FOG REMOVAL PH ADJUSTMENT SEGREGATION

7 SCREENING LARGE SOLIDS CAN CLOG DOWNSTREAM PROCESSES REMOVING ORGANIC SOLIDS WILL REDUCE LOAD ON THE FACILITY AUTOMATIC CLEANING ARE BEST OPTION

8 FOG REMOVAL HIGH LEVELS OF FOG CAN ARE TOXIC TO BIOLOGICAL SYSTEMS IF FOG IS VERY HIGH USE ROPE SKIMMER OR OTHER EQUIPMENT TO REMOVE

9 FLOW EQUALIZATION MAINTAINING AN EVEN FLOW RATE IS CRITICAL TO AN EFFICIENT SYSTEM. PROVIDES LOCATION TO ADJUST ph MORE EASILY PROVIDE ADEQUATE RETENTION TIME AND GOOD MIXING AIR CAN HELP REDUCE ODORS

10 ph ADJUSTMENT EXTREME SWINGS IN ph HAVE A NEGATIVE IMPACT ON BIOLOGICAL SYSTEMS. ADJUST ph IN LIFT STATION OR EQUALIZATION TANK PRIOR TO BIOLOGICAL TREATMENT

11 AEROBIC / ACTIVATED SLUDGE SYSTEMS ACTIVATED SLUDGE IS A AEROBIC, BIOLOGICAL PROCESS WHICH USES MICROORGANISMS TO REMOVE BIODEGRADABLE ORGANIC POLLUTANTS FROM WASTEWATER SO IT CAN BE DISCHARGED TO A RECEIVING STREAM OR MUNICIPAL WASTEWATER FACILITY GOALS OF PROCESS REMOVE COD/BOD AND NUTRIENTS MAJOR COMPONENTS TANK BLOWERS DIFFUSERS MIXING PUMPS

12 ACTIVATED SLUDGE PROCESS THE PROCESS OF TREATING WASTEWATER USING AEROBIC MICROORGANISMS TO CONSUME SOLUBLE ORGANIC WASTE. ORGANICS (WASTE) + O 2 + MICROORGANISMS+ NUTRIENTS + INERT MATTER CO 2 + H 2 O + NEW MICROORGANISMS + INERT MATTER YIELD RATE (# TSS/# COD)

13 BENEFITS OF ACTIVATED SLUDGE PROCESS WELL ESTABLISHED TECHNOLOGY (DISCOVERED IN 1913) MOST COMMONLY USED METHOD TO TREAT WASTEWATER FOR DISCHARGE TO SURFACE WATERS EXTREMELY HIGH EFFLUENT QUALITY ABILITY TO REMOVE NUTRIENTS IN ADDITION TO ORGANICS

14 LIMITATIONS OF ACTIVATED SLUDGE PROCESS EXTREMELY HIGH ENERGY USAGE DUE TO NEED FOR AIR. (50% OF PLANTS ENERGY USAGE) SUSCEPTIBLE TO UPSETS MODERATE LOADING RATES HIGH YIELD RATES / SLUDGE PRODUCTION

15 AEROBIC TREATMENT BASIN PROVIDE A COMPLETE MIX TANK WITH FINE BUBBLE DIFFUSION OF AIR TO PROVIDE MAXIMUM POSSIBLE OXYGEN TRANSFER EFFICIENCY. MAINTAIN CONSISTENT DISSOLVED OXYGEN LEVEL UTILIZING VFDs OR MODULATING VALVES. PROVIDE MEANS FOR FOAM CONTROL

16 ACTIVATED SLUDGE IMPORTANT PARAMETERS DISSOLVED OXYGEN (D.O.) THE AMOUNT OF AIR AVAILABLE TO MICROORGANISMS IN THE AERATION BASIN TOO MUCH DO WASTES ENERGY & CAN PROMOTE GROWTH OF DETRIMENTAL ORGANISMS TOO LITTLE D.O. CAN CAUSE FILAMENTOUS GROWTH, BACTERIA DIE-OFF AND SERIOUS ODORS OXIDATION REDUCTION POTENTIAL (ORP) INDICATION OF THE CONDITION OF THE AERATION BASIN ORP READING OVER 200 mv INDICATION Possible that oxidizing chemical is entering the system mv Normal Operating Range Below -150 mv Below -300 mv Anoxic Range System is Septic

17 ACTIVATED SLUDGE IMPORTANT PARAMETERS MIXED LIQUOR SUSPENDED SOLIDS (MLSS) THE TOTAL SUSPENDED SOLIDS WITHIN THE ACTIVATED SLUDGE SYSTEM. TYPICALLY WITHIN A RANGE OF 3,000 6,000 MG/L DEPENDING ON FM* RATIO AND SLUDGE AGE. TOO HIGH OR LOW CAN CREATE ENVIRONMENT FOR HARMFUL MICROORGANISMS TO PROPAGATE MEAN CELL RESIDENCE TIME (MCRT) AKA: SLUDGE AGE THE AVERAGE TIME THAT A MICROORGANISM WILL SPEND IN THE ACTIVATED SLUDGE SYSTEM TYPICAL RANGE IS 5-15 DAYS WITH 30 DAYS AS MAXIMUM FOR EXTENDED AERATION PLANTS *FOOD TO MICROORGANISM RATIO

18 ACTIVATED SLUDGE IMPORTANT PARAMETERS HYDRAULIC RETENTION TIME (HRT): THE AVERAGE AMOUNT OF TIME THAT WATER REMAINS IN THE AERATION BASIN NEEDS TO BE LONG ENOUGH TO PROVIDE ADEQUATE TIME TO COMPLETELY TREAT WASTEWATER. FOOD TO MICROORGANISM RATIO: A RATIO OF THE AMOUNT OF BOD RECEIVED TO THE POPULATION OF MICROORGANISMS IN A WASTEWATER PLANT. TYPICAL RANGE IS 0.15 TO 0.5 OUTSIDE OF TYPICAL RANGE CAN CAUSE OPERATIONAL PROBLEMS.

19 WHEN ACTIVATED SLUDGE GOES BAD

20 ACTIVATED SLUDGE - SANITIZERS SANITIZERS USED IN FOOD AND BEVERAGE PLANTS CAN HAVE DETRIMENTAL IMPACT ON ACTIVATED SLUDGE SYSTEMS PERACETIC ACID CAN BE NEUTRALIZED USING BISULFITE QUATERNARY AMMONIA COMPOUNDS CAN BE NEUTRALIZED BY SPECIAL CHEMICALS

21 ANAEROBIC SYSTEMS GOALS OF PROCE SS RE MOVE COD/BOD BIOLOGICAL SOLIDS RE DUCT ION E QUIPME NT T ANK MIXE RS GAS COLLE CT ION & RE MOVAL

22 ANAEROBIC TREATMENT SYSTEMS ANAEROBIC TREATMENT IS AN ANAEROBIC, BIOLOGICAL PROCESS WHICH USES MICROORGANISMS TO REMOVE BIODEGRADABLE ORGANIC POLLUTANTS FROM WASTEWATER SO IT CAN BE DISCHARGED TO A RECEIVING STREAM OR MUNICIPAL WASTEWATER FACILITY GOALS OF PROCESS REMOVE COD/BOD AND NUTRIENTS REDUCE ORGANIC SOLIDS MAJOR COMPONENTS COVERED TANK MIXING PUMPS GAS COLLECTION SYSTEM

23 ANAEROBIC TREATMENT PROCESS THE PROCESS OF TREATING WASTEWATER USING ANAEROBIC MICROORGANISMS TO CONSUME SOLUBLE ORGANIC WASTE. ORGANICS (WASTE) CH 4 + NEW MICROORGANISMS + INERT MATTER YIELD RATE (# TSS/# COD)

24 ANAEROBIC TREATMENT PROCESS PUT ANOTHER WAY

25 BENEFITS OF ANAEROBIC TREATMENT PRODUCES A USABLE BY PRODUCT METHANE MUCH HIGHER LOADING RATES WHEN COMPARED TO ACTIVATED SLUDGE MUCH LOWER YIELD RATES / SLUDGE PRODUCTION

26 LIMITATIONS OF ANAEROBIC TREATMENT MORE COMPLICATED PROCESS TO CONTROL CANNOT REMOVE AS MUCH ORGANIC WASTE AS ACTIVATED SLUDGE CANNOT REMOVE NUTRIENTS SUCH AS PHOSPHORUS AND NITROGEN SLUDGE DOES NOT TYPICALLY SETTLE LEADING TO HIGHER SOLIDS LIQUID SEPARATION COST

27 ANAEROBIC SYSTEMS IMPORTANT PARAMETERS TEMPERATURE TEMPERATURE OF F NEEDED TO MAINTAIN PROPER MICROBIOLOGICAL POPULATION PH ANAEROBIC MICROORGANISMS ARE SENSITIVE TO PH CHANGES TYPICAL RANGE IS LOW PH REDUCES METHANE PRODUCTION AND CAUSES BUILD UP OF VFA

28 ANAEROBIC SYSTEMS IMPORTANT PARAMETERS VOLATILE FATTY ACIDS (VFA) GENERATED IN THE ANAEROBIC DIGESTION PROCESS. AN ACCUMULATION OF VFA IN THE SYSTEM CAN DROP THE PH CAUSING A SOUR DIGESTER. ALKALINITY PREVENTS FLUCTUATION IN PH DIGESTION CREATES IS OWN ALKALINITY VFA/ALKALINITY RATIO: OFTEN CAN BE A BETTER INDICATOR OF DIGESTER PROBLEMS BECAUSE IT WILL SHOW BEFORE A DROP IN PH. TYPICAL BEST RANGE IS LESS THATN 0.1.

29 ANAEROBIC SYSTEMS IMPORTANT PARAMETERS MIXED LIQUOR SUSPENDED SOLIDS (MLSS) THE TOTAL SUSPENDED SOLIDS WITHIN THE ANAEROBIC BASIN TYPICALLY WITHIN A RANGE OF 20,000-30,000 MG/L DEPENDING ON F.M. RATIO AND SLUDGE AGE. TOO HIGH OR LOW CAN CREATE ENVIRONMENT FOR HARMFUL MICROORGANISMS TO PROPAGATE BIOGAS QUALITY CHANGES IN GAS QUALITY CAN BE INDICATORS OF PERFORMANCE PROBLEMS METHANE: 50-75% CARBON DIOXIDE: 25-50% NITROGEN: 1-5% HYDROGEN SULFIDE: <1% USED TO ADJUST WASTING RATE

30 ANAEROBIC TREATMENT BASIN

31 ANAEROBIC GAS HANDLING EQUIPMENT

32 SOLIDS LIQUID SEPARATION

33 GRAVITY CLARIFIERS IN A HEALTHY SYSTEM THE MLSS WILL SETTLE BY GRAVITY. AN UPSET OR OVERLOADED SYSTEM MAY REQUIRE CHEMICAL ADDITION RETURN SOLIDS TYPICALLY 1%. REQUIRE LARGE FOOTPRINT

34 DISSOLVED AIR FLOATATION (DAF) USE MICROSCOPIC AIR BUBBLES TO FLOAT SOLIDS. TYPICALLY USED IN CONJUNCTION WITH COAGULANTS AND/OR FLOCCULANTS RETURN SOLIDS TYPICALLY 35% REQUIRES MUCH SMALLER FOOTPRINT

35 MEMBRANE SYSTEMS USE MEMBRANES AS A PHYSICAL BARRIER TO SEPARATE SOLIDS FROM TREATED WATER. EFFLUENT NOT AS INFLUENCED BY UPSETS ELIMINATES THE NEEDS FOR COAGULANTS AND FLOCCULANTS.

36 SLUDGE THICKENING / DEWATERING

37 SLUDGE THICKENING / DEWATERING INCREASE SOLIDS CONTENT (LOWER MOISTURE) OF SLUDGE BEFORE DISPOSAL. REDUCES THE VOLUME / WEIGHT NECESSARY FOR DISPOSAL TO SAVE COST. THICKENED SLUDGE GENERALLY < 15% SOLIDS & CAN BE PUMPED DEWATERED SLUDGE GENERALLY > 15% SOLIDS & MUST BE HANDLED AS A SOLID

38 PRESSES MORE OFTEN USED TO THICKEN WASTE SOLIDS PRIOR TO DISPOSAL. TYPICAL WASTE SOLIDS ARE 10-30% TYPICALLY REQUIRES COAGULANT AND/OR FLOCCULANT TYPES BELT PRESSES SCREW PRESSES ROTARY PRESSES

39 CENTRIFUGE CAPABLE OF PRODUCING UP TO 40% CAKE EFFLUENT QUALITY IS TYPICALLY POOR VERY HIGH ENERGY USAGE NEED REGULAR MAINTENANCE

40 COMPARISON OF AEROBIC AND ANAEROBIC SYSTEMS PARAMETER AEROBIC ANAEROBIC TREATMENT QUALITY SUITABLE FOR DIRECT DISCHARGE TO SURFACE WATER. CAN REMOVE NITROGEN AND PHOSPHORUS TO LOW LEVELS EFFLUENT REQUIRES ADDITIONAL TREATMENT PRIOR TO DISCHARGE. NO NITROGEN OR PHOSPHORUS REMOVAL. ORGANIC LOADING KG COD/M 3 PER DAY 3-20 KG COD/M 3 PER DAY YIELD RATE KG VSS/KG COD KG VSS/KG COD

41 COMPARISON OF AEROBIC AND ANAEROBIC SYSTEMS PARAMETER AEROBIC ANAEROBIC COSTS ENERGY HIGH DUE TO AERATION CAN GENERATE ITS OWN ENERGY CHEMICAL LOW DUE TO NATURAL SETTLING HIGH DUE LACK OF SETTLING SLUDGE DISPOSAL DEPENDS ON LOADING AND SYSTEM SIZE DEPENDS ON LOADING AND SYSTEM SIZE