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

2. CONTENT WATER – THE CURRENT SITUATION IN SA. WHY TREAT WASTEWATER?
TREATMENT OBJECTIVES.
CURRENT TREATMENT OPTIONS.
CURRENT TRENDS.
THE ACTIVATED SLUDGE PROCESS.
THE TRICKLING FILTER.
COMPARISON OF ACTIVATED SLUDGE AND TRICKLING FILTERS .
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. MAJOR AEROBIC BIOLOGICAL PROCESSES
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

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

11. Trickling Filter Integrated with Ponds (Petro'M)

12. Type of Growth Common Name Use
SUSPENDED GROWTH
ACTIVATED SLUDGE (AS)
COD REMOVAL (NITRIFICATION) / P REMOVAL
AERATED LAGOONS
COD REMOVAL (NITRIFICATION)
ATTACHED GROWTH
TRICKLING FILTERS
COD 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

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
GRIT REMOVAL
BIO-REACTORS
SST
RAW IN
SCREENS
PST
DISPOSAL
RAS
WASTING
DISINFECTION
SLUDGE TREATMENT
EFFLUENT RE-USE

15. ATHLONE WWTW

16. POTSDAM WWTW: SURFACE AERATION

17. ADVANTAGES / DISADVANTAGES OF THE ACTIVATED SLUDGE PROCESS
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
A TYPICAL TRICKLING FILTER
STONES
FEED
EFFLUENT

21. ADVANTAGES AND DISADVANTAGES OF TRICKLING FILTERS
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