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THE COMPARISON OF WASTEWATER TREATMENT METHODS AND THEIR USE FOR IRRIGATION Presented by: Michael Fynn Date: Tuesday 3 rd September 2007.

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Presentation on theme: "THE COMPARISON OF WASTEWATER TREATMENT METHODS AND THEIR USE FOR IRRIGATION Presented by: Michael Fynn Date: Tuesday 3 rd September 2007."— Presentation transcript:

1 THE COMPARISON OF WASTEWATER TREATMENT METHODS AND THEIR USE FOR IRRIGATION Presented by: Michael Fynn Date: Tuesday 3 rd September 2007

2 CONTENT 1.WATER – THE CURRENT SITUATION IN SA. 2.WHY TREAT WASTEWATER? 3.TREATMENT OBJECTIVES. 4.CURRENT TREATMENT OPTIONS. 5.CURRENT TRENDS. 6.THE ACTIVATED SLUDGE PROCESS. 7.THE TRICKLING FILTER. 8.COMPARISON OF ACTIVATED SLUDGE AND TRICKLING FILTERS. 9.EFFLUENT RE-USE.

3 CURRENT SITUATION SA SITUATED IN SEMI-ARID PART OF AFRICA 450mm RAIN/YEAR ; WORLD AVERAGE IS 860mm/YEAR TOTAL FLOW FROM ALL RIVERS IN SA IS million cu.m WHICH IS LESS THAN ½ TOTAL ANNUAL FLOW FROM ZAMBEZI RIVER. GLOBAL WARMING AN EVER PRESENT REALITY

4 WHY TREAT WASTEWATER? THE MOST BASIC ANSWER IS TO CLEAN DIRTY WATER. TREATMENT FACILITIES SIMPLY COMPRESS THE ORGANIC DECOMPOSITION PROCESSES WHICH TAKE PLACE IN NATURE. THIS IS PERFORMED BY A COMBINATION OF PHYSICAL, BIOLOGICAL, AND CHEMICAL TREATMENT STAGES. NATURE (RECEIVING WATERS) CAN ONLY ACCEPT SMALL AMOUNTS OF SEWAGE BEFORE BECOMING POLLUTED, THAT IS, NATURAL BACTERIA FEED ON THE SEWAGE ORGANICS AND CREATE AN ABNORMAL AMOUNT OF DISSOLVED OXYGEN UPTAKE.

5 BIOLOGICAL TREATMENT OBJECTIVES IN THE CASE OF DOMESTIC WASTEWATER TREATMENT THE OBJECTIVE OF BIOLOGICAL TREATMENT IS TO STABILIZE THE ORGANIC CONTENT. TO REMOVE SUCH NUTRIENTS SUCH AS PHOSPHORUS AND NITROGEN. PROCESS TYPES AEROBIC ANOXIC ANAEROBIC COMBINED PROCESSES

6 THE TREATMENT OF THE WASTEWATER IS ACHIEVED BY BILLIONS OF NATURALLY OCCURING BACTERIA THESE BACTERIA REQUIRE MEDIA ON OR IN WHICH TO GROW IN ORDER TO BE IN THE BEST POSITION TO UTILIZE THE WASTEWATER AS FOOD TWO TYPES OF GROWTH ENVIRONMENTS SUSPENDED GROWTH ENVIRONMENT FIXED GROWTH ENVIRONMENTS MAJOR AEROBIC BIOLOGICAL PROCESSES

7 Several alternative process configuration using trickling filter technology are available. conventional bio-filter biofiltration solids contact (BFSC) process biofiltration with high rate circulation pond enhanced treatment and operation (PETRO) process integrated anaerobic pond biofiltration process integrated biofiltration activated sludge (BFAS) process

8 Dual Stage Trickling Filtration Process Polishing Nitrification Trickling Filter Process

9 Primary Clarifier Trickling Filter Solids Contact Box Secondary Clarifier Humus Trickling Filter/Solids Contact Treatment Process

10

11 Trickling Filter Integrated with Ponds (Petro'M)

12 Type of Growth Common NameUse SUSPENDED GROWTH ACTIVATED SLUDGE (AS)COD REMOVAL (NITRIFICATION) / P REMOVAL AERATED LAGOONSCOD REMOVAL (NITRIFICATION) ATTACHED GROWTH TRICKLING FILTERSCOD REMOVAL. NITRIFICATION ROUGHING FILTERS (TRICKLING FILTERS WITH HIGH HYDRAULIC LOADING RATES) COD REMOVAL ROTATING BIOLOGICAL CONTACTORS COD REMOVAL (NITRIFICATION) COMBINED SUSPENDED & ATTACHED GROWTH ACTIVATED BIOFILTER PROCESS COD REMOVAL (NITRIFICATION)

13 SUSPENDED GROWTH ---THE ACTIVATED SLUDGE PROCESS ACTIVATED SLUDGE HAS BEEN THE SUSPENDED MEDIA TREATMENT OPTION OF CHOICE. WHY? EXCELLENT COD REMOVAL. COMPLETE NITRIFICATION IS ACHIEVABLE. LOWER PHOSPHATE DISCHARGE IS POSSIBLE. IMPROVED DISINFECTION DUE TO LOWER AMMONIA AND SUSPENDED SOLIDS IN FINAL EFFLUENT.

14 BRIEF OVERVIEW OF THE AS PROCESS RAW IN SCREENS GRIT REMOVAL PST BIO-REACTORS SST SLUDGE TREATMENT DISINFECTION DISPOSAL RAS WASTING EFFLUENT RE-USE

15 ATHLONE WWTW

16 POTSDAM WWTW: SURFACE AERATION

17 ADVANTAGES / DISADVANTAGES OF THE ACTIVATED SLUDGE PROCESS ADVANTAGES CAN ADAPT TO MINOR PH, ORGANIC AND TEMP CHANGES. SMALL AREA REQUIRED. DEGREE OF NITROGEN REMOVAL IS CONTROLABLE. MINOR ODOUR PROBLEMS. DISADVANTAGES HIGH OPERATING COSTS. SKILLED OPERATIONAL STAFF REQUIRED. ELECTRICITY COST HIGH. SENSITIVE TO SHOCK LOADS. REQUIRES CONTINUOUS AIR SUPPLY.

18 ATTACHED GROWTH ---- THE TRICKLING FILTER WHAT IS A TRICKLING FILTER? A WASTEWATER TREATMENT SYSTEM THAT BIODEGRADES ORGANIC MATTER AND CAN ALSO BE USED TO ACHIEVE NITRIFICATION. THE WASTEWATER TRICKLES THROUGH A CIRCULAR BED OF COARSE STONES OR PLASTIC MATERIAL..

19 ATTACHED GROWTH ---- THE TRICKLING FILTER. CONT A ROTATING DISTRIBUTOR) EVENLY DISTRIBUTES THE WASTEWATER FROM ABOVE THE BED. THE MICROORGANISMS IN THE WASTEWATER ATTACH THEMSELVES TO THE BED (ALSO KNOWN AS THE FILTER MEDIA), WHICH IS COVERED WITH BACTERIA. THE BACTERIA BREAK DOWN THE ORGANIC WASTE AND REMOVE POLLUTANTS FROM THE WASTEWATER.

20 A TYPICAL TRICKLING FILTER DISTRIBUTOR ARMS STONES FEED EFFLUENT

21 ADVANTAGES AND DISADVANTAGES OF TRICKLING FILTERS ADVANTAGES GOOD QUALITY COD REMOVAL ( 80%-90%). MODERATE OPERATING COSTS ( LOWER THAN ACTIVATED SLUDGE). WITHSTANDS SHOCK LOADS BETTER THAT OTHER BIOLOGICAL PROCESSES. DISADVANTAGES HIGH CAPITAL COSTS. CLOGGING OF DISTRIBUTOR ARMS OR BEDS. POSSIBLE ODOUR PROBLEMS.

22 COMPARISON OF THE TWO SYSTEMS CAPITAL COSTS … ACTIVATED SLUDGE LOWER. OPERATING COSTS … BIOFILTER LOWER. ENERGY COSTS…. BIOFILTER LOWER. CALIBRE OF OPERATIONAL STAFF… FOR TF CAN BE SEMI- SKILLED. ASP …REQUIRES FAIRLY SKILLED PROCESS CONTROLLERS. THIS INCURS HIGHER OPERATING COSTS. EFFLUENT QUALITY …. ASP PRODUCES A BETTER QUALITY FINAL PRODUCT. EFFLUENT NUTRIENT VALUE … TF EFFLUENT HAS MORE NITRATE AND PHOSPHATES THUS HAVING A GREATER FERTILIZER VALUE.

23 WHERE WOULD TRICKLING FILTER BE AN APPROPRIATE TECHNOLOGY ? SMALL RURAL COMMUNITIES. WHEN ONLY SKILLED STAFF ARE AVAILABLE NO SLUDGE AGE CALCULATIONS NEEDED NO SLUDGE WASTING REQUIRED. WHEN ELECTRICITY SUPPLY IS LIMITED. WHEN A WELL NITRIFIED EFFLUENT IS REQUIRED FOR IRRIGATION.

24 ENERGY COST OF TREATMENT TRICKLING FILTER KWH/ML ACTIVATED SLUDGE KWH/ML ADVANCED TREATMENT WITH NITRIFICATION KWH/ML

25 EFFLUENT RE-USE IRRIGATION HAS TWO REQUIREMENTS. THE WATER REQUIREMENTS OF THE PLANT. THE NUTRIENT REQUIREMENTOF THE PLANT. WITH FULLY NITRIFIED EFFLUENT FROM A TRICKLING FILTER WORKS ONE CAN EXCEED THE NUTRIENT REQUIREMENT BEFORE ONE REACHES THE WATER REQUIREMENT OF THE PLANT. AS A RESULT NITRATES MAY INFILTRATE THE UNDERGROUND WATER SUPPLY WHICH MUST BE AVOIDED. THEREFORE TRICKLING FILTER WASTEWATER APPLICATION RATES MUST BE CAREFULLY MONITORED. WITH ACTIVATED SLUDGE ONE CAN CONTROL THE NITRATE AND THE WATER REQUIREMENT OF THE PLANT AT THE SAME TIME.

26 POTSDAM WWTW: EFFLUENT RE-USE

27 APPROPRIATE TECHNOLOGY REQUIRES TRAINED STAFF STAFF TO BE TRAINED IN THE OPERATION OF THEIR WORKS. OPERATIONS STAFF TO BE OBSERVANT AND USE THEIR FIVE SENSES WHEN EVALUATING THEIR PROCESS. COUNTER-PRODUCTIVE TO HAVE APPROPRIATE TECHNOLOGY OPERATED BY POORLY TRAINED STAFF. MAINTENANCE CRITICAL..

28 SUMMARY WE HAVE DISCUSSED ONLY TWO OF MANY TREATMENT OPTIONS. IT IS CLEAR THAT THE BEST SOLUTION IN A PARTICULAR CASE IS OFTEN A COMPROMISE BETWEEN MORE THAN ONE OPTION AS WELL AS ECONOMIC AND ENVIRONMENTAL CONSIDERATIONS. LOOKING BACK ON THE SHORT HISTORY AND SUCESSES OF OUR YOUNG DEMOCRACY I AM SURE THAT WE ARE WELL UP TO THE TASK OF CHOOSING APPROPRIATE TECHNOLOGIES. THANK YOU FOR YOUR ATTENTION

29 Conclusion Let us work together for a better city


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