Eleventh International Water Technology Conference, IWTC Sharm El-Sheikh, Egypt 209

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1 209 FUTURE TRENDS TOWARDS USING OF ALTERNATIVE BEST AVAILABLE TECHNIQUES (BAT) AS A PRE-DESIGN STEP OF ANAEROBIC WASTEWATER TREATMENT PLANTS. APPLICATIONS FOR MEDIUM STRENGTH DOMESTIC SEWAGE Walid Abdel-Halim 1, D. Weichgrebe 2, and K.-H. Rosenwinkel 2 1 Housing and Building National Research Center (HBRC), Egypt abdel-halim@gmx.de 2 Institute for Water Quality and Waste Management (ISAH), University of Hanover, Germany ABSTRACT Determination of anaerobic biodegradability of wastewater under different values of process parameters is most promising for resolving anaerobic treatment problems. In this study the Anaerobic Batch Test (ABT) technique was used as alternative Best Available Technique (BAT) to determine the biodegradability, sludge bioactivity and biogas production for the municipal wastewater (raw and pre-settled) as a substrate inoculated and incubated with two different types of sludge (granular and digested sludge) for different time periods up to 48 hours. The main aim of this work was to investigate the effect of different anaerobic process parameters such as; type and composition of wastewater, Hydraulic Retention Time (HRT), Sludge Loading Rate (SLR), bioactivity of sludge on the speed of the biodegradation process and biogas production (quantity and quality) as well, under the different inoculation sludge types with different biomass content at mesophilic temperature condition. A comparison between the methanogenic bio-activity of both of granular and digested sludge at different SLRs was set as a potential to predict the design parameters of UASB reactor. Also Triphenytetrazoliumchloride (TTC-test) was experimented as a pre-step to evaluate sludge bio-activity, thus its results were compared to those obtained from ABT to decide the future applicability of TTC test as a simple, quick indication of anaerobic sludge bio-activity. Keywords: anaerobic batch test; anaerobic biodegradability; domestic wastewater treatment; sludge bioactivity INTRODUCTION Anaerobic digestion has become the most frequently used method for the treatment of medium and high concentration wastewaters, due to the economy of the process, and the low generation of surplus sludge. It is widely accepted as a low cost treatment technology of domestic and industrial wastewater (Van Haandel and Lettinga, 1994).

2 210 Different anaerobic technologies have been applied to the treatment of domestic wastewater. Upflow Anaerobic Sludge Blanket UASB reactor still is the most frequency used reactor in full-scale installation and has proven to be effective even in the treatment of low strength municipal wastewater at tropical conditions (Lettinga et al, 1993). In the UASB process, wastewater flows through a sludge bed (granular or digested), where different physical and biochemical mechanisms act in order to retain and biodegrade organic substances. Because the speed of the biodegradability process depends on several parameters such as; type and composition of wastewater, Hydraulic Retention Time (HRT), Sludge Loading Rate (SLR), methanogenic bioactivity of sludge, then determination of biodegradability of wastewater under different values of these parameters is most promising for resolving anaerobic treatment problems. Several bioassay techniques were used to distinguish between biodegradable and nonbiodegradable organics, they are essential for determining biodegradability since no chemical procedure is available (Gledhill, 1979). These techniques based their method on measurement of excess gas volume (CO 2 +CH 4 ) produced after addition of substrates to anaerobic seed incubated in sealed bottles (Shelton et al. 1984). The first international standard for evaluation of the ultimate anaerobic biodegradability of organic compounds in digested sludge was issued in 1995 (ISO 11734, 1995). Present tendency of many researchers is to improve and automate the measurement procedure leading to more accurate results and easier, sufficient measurements. Lot of recent development of updated guidelines of the anaerobic batch tests performing as well as application instructions and limits are the focus of interest of standard production organizations in Germany such as ATV German Association for Water, wastewater and Waste (ATV-DVWK-IG 5.1, 2004) and VDI Association of German Engineers (VDI-4630, 2003) as well as IWA-working group of anaerobic digestion jointed with Joint Research Center of the European Commission to strength the activities on harmonization of anaerobic biodegradation, activity and inhibition assays (IWA-AD and JRC of EU, 2002). Also the ISAH (Institute of Water Quality and Waste Management, University of Hanover) has a lot of experience in the field of performing and application of the anaerobic batch tests in field of domestic and industrial wastewater as well as bio-waste as a potential to develop of biogas energy. Then as a part of the activity of ISAH in that field, the main objectives of this study are: 1- Using of the best available techniques of the anaerobic batch tests to determine the biodegradation of municipal wastewater (raw and pre-settled) inoculated with granular and digested sludge at different hydraulic retention times and different sludge loading rates. 2- Set a comparison between the methanogenic bio-activity for the both granular and digested sludge as a potential of UASB reactor design. 3- Test of applicability of the TTC test as an indicator of the sludge bio-activity using the municipal wastewater, compared to the results obtained from the anaerobic batch tests as a potential to decide the precision of TTC test for that purpose.

3 211 Methodology Materials and Methods: Substrates: Raw and pre-settled wastewaters were collected from wastewater treatment plant treats a complex domestic wastewater (75% domestic+ 25% industrial). Wastewater samples were analysed for physico-chemical parameters. Also a sample of sodium-acetate (CH 3 COONa) as a reference substrate (with good anaerobic biodegradable) was prepared in the labrotary to be used for the results comparison. Table 1 shows the characteristics values of the used wastewaters and sodium-acetate. Table 1: Concentration characteristics of the used substrates. Org. CODhom CODfilt ph TSS VSS VSS Substrate acids TSS/CODhom mg/l mg/l mg/l % mg/l mg/l Raw wastewater Pre-settled wastewater Acetate Inoculation biomass: Anaeroobic biomass used for the inoculation of the samples was collected; from anaerobic digester treats primary and activited sludge of the municipal wastewater treatment plant (digested sludge) as well as granular sludge from UASB reactor treats Alcohol effluent wastes. Both sludges were preactivited at 35±2 C for hours before using in the tests. To measure the biogas production due to sludge fermentation the equivalent amount of each sludge was incubated without any substrate (Blank bottle).table 2 shows the concentration characteristics of the used inoclulation sludges. Table 2: Concentration characteristics of the used inoculation biomass (sludges). Sludge type Granular sludge Digested sludge CODhom CODfilt ph TS VS VS Org. acids g/l g/l g/l % g/l g/l , Triphenyltetrazoliumchloride (TTC)-Test: Bio-activity test of the sludge had performed to determine the relative change in the sludge activity due to anaerobic incubation with the wastewater ; raw and pre-settled. The change of the activity determined by use of NANOCOLOR TTC/sludge activity; method and the

4 212 change expressed in the form of the bio-activity of the sludge when incubated with the wastewater wether raw or pre-settled and the results are measured as a concerntration of triphenlyformazane(ctpf) formed in µg and then the biochemical activity(as) of each case calculated using the following equation; Biochemical activity (As) ( µg Formazane/mg dry sludge mass) = CTPF/ Cs ; where Cs = V * DSM "V: Volume of the sludge sample in ml and DSM: Dry sludge mass in g/l when dried at 105 C". Anaerobic batch Tests (ABTs): were performed in 500 ml glass bottles sealed by silicon stoppers. Half of samples of raw and pre-settled wastewaters were inoculated with anaerobic granular sludge with different initial Sludge Loading Rates (SLR) of 0.2, 0.3, and 0.5 g COD substrate/g VS sludge and the other half of samples were inoculated with anaerobic digested sludge with different initial SLRs of 0.025, 0.05, and 0.1 g COD substrate/g VSS sludge. Acetate was used as a reference substrate. Table 3 illustrates the initial volumes of substrates and sludge in the bottles to reach to the required SLR inclusive also the quantity of biomass in each bottle. Table 3: Substrates and sludge amounts in the test bottles. Substrate Acetate Raw wastewater Pre-settled wastewater Weight g Granular sludge SLR g COD/g Vs.d VS g Substrate s volume ml COD amount ml Weight g Digested sludge SLR g COD/g VS.d VS g Substrate s volume ml COD amount ml Incubation: All samples were incubated at 37 C in shaking water bath provided with thermostat to control the temperature or in water bath provided with a magnetic stick connected to control device and stirrer had put inside the bottles for mixing between substrate and sludge to guarantee a good contact between them during the test time. Pressure inside bottles was measured with digital pressure device (0 to 4 bars) provided with needle. Figure 1 illustrates the two different incubation methods used in the ABTs.

5 a. Thermostat water bath with magnetic stick and stirrer 1. b. Thermostat shaking water bath Figure 1: Alternative two methods of incubation during ABT. Analytical methods: - Filtered COD (CODfilt.), Total COD (CODhom), ph, Volatile Fatty Acids (VFA), TSS, VSS were measured for wastewater, sludge and the mixture before and after incubation. Also pressure inside bottles were measured during incubation according to the planed time intervals using digital pressure gauge provided by needle to penetrate through the silicon stopper of the bottles as shown in figure 2. At the end of the test, Gas Chromograph (GC- test) was done to measure the percentage of CO2 and CH4 in the bottles after incubation period for 48 hrs. All of analyses and determination were carried out as stated in (APHA, 1998). - The relative change of the biochemical sludge activity due to wastewater compounds was measured for each of digested and granular sludge by means of change of the Dehydrogenase activity (DHA) which is caused by wastewater substances using 2,3,5-Triphenytetrazoliumchloride (TTC-test) to be compared to the bioactivity of sludge obtained from ABTs.

6 214 Figure 2: Digital pressure gauge used for pressure measurement inside bottles along ABT incubation RESULTS AND DISCUSSION TTC-test: As it is stated in the methodology, the relative change of the biochemical sludge activity due to wastewater compounds was measured for each of digested and granular sludge by means of change of the Dehydrogenase activity (DHA) which is caused by wastewater substances. The final results of the biochemical activity was; 0.76, 1.13, 1.27 µg Formazane/mg dry sludge mass for the samples of; only granular sludge, granular sludge with raw wastewater and pre-settled wastewater respectivily as well as 0.35, 0.65,0.59 µg Formazane/mg dry sludge mass for the samples of; only digested sludge, digested sludge with raw wastewater and pre-settled wastewater respectivily. These values indicate that the both substrate whether raw or pre-settled wasetwater are good bio-activator and have a stimulating influence on the increasement of the biocemical activity of sludge. The calculated increment ratios of the bio-activity of the both sludges are 48.7%, 53.6 % in case of raw and pre-settled wastewater with granular sludge as well as 26.35%, 25.98% in case of raw and presettled wastewater with digested sludge respectivily. Results obtained from TTC-Test are compared to those obtained from ABTs to determine the accuracy of using of the TTC test as a pre-step before ABTs to decide if the substrate has a significant biodegradability or not and according to the positive resluts of the TTC-test, the performing of ABTs will be decided. As it will be mentioned later on paragraphs,results obtained from the performed TTC biochemical activity of sludge were almost similar to those obtained from the determination of the sludge bioactivity obtained from ABT. Anaerobic Batch Test ABT: The amount of produced biogas was calculated according to the measured pressures from different substrates with the different sludge types (digested sludge DS and granular (pellets) sludge PS ) at different SLRs. Therefore CH4 production was also determined. Figure 3 shows the CODfilt,-, CODss,- and CODtot-removal efficiencies for all substrates in dependence of SLR and sludge type.

7 215 Also specific biogas production (ml CH 4 /g COD rem ), and sludge methanogenic bioactivity (g CH 4 -COD rem. /g VS.d) were determined. The results from ABT for each of digested and granular sludge were compared together to determine the anaerobic sludge bioactivity of each with raw RW and pre-settled PW wastewater. Figure 4 shows the total methane CH4-gas production for different wastewaters along different SLRs. COD Removal ( % ) ,025 0,000 0,075 0,050 0,100 0,125 0,150 0,175 0,225 0,200 0,250 0,300 0,275 SLR (gcod/gvss) 0,350 0,325 0,375 0,400 0,425 0,450 0,500 0,475 0,525 0,550 RW/ DS- CODfilt. RW/ DS- CODss RW/ DS- CODtot. PW/ DS- CODfilt. PW/ DS- CODss PW/ DS- CODtot. Acetate/ DS RW/ PS- CODfilt. RW/ PS- CODss RW/ PS- COD tot PW/ PS- CODfilt. PW/ PS- CODss PW/ PS- CODtot. Acetate/ PS Figure 3: COD removal efficiency (Filtered, suspended and total) along different SLRs. Where: RW: raw wastewater PW: pre-settled wastewater PS: pellets Granular sludge DS: Digested sludge RW/PS: raw wastewater inoculated and incubated with pellets sludge RW/DS: raw wastewater inoculated and incubated with digested sludge PW/PS: pre-settled wastewater inoculated and incubated with pellets sludge PW/DS: pre-settled wastewater inoculated and incubated with digested sludge

8 216 Total CH4-Gas (ml) ,05 0,025 0,075 0,125 0,1 0,175 0,15 0,2 0,25 0,225 0,275 0,325 0,3 SLR (gcod/gvss) 0,375 0,35 0,4 0,45 0,425 0,475 0,525 0,5 0,575 0,55 0,6 RW/ DS RW/ PS PW/ DS PW/ PS Acetate/ DS Acetate/ PS Figure 4: CH 4 -Gas production from different substrates at different SLRs. As well as Figure 5 shows the specific biogas production calculated based on the inflow COD, TSS, VSS and the volume of the inflow substrate for the raw and presettled wastewater inoculated with granular and digested sludge at different SLRs; 0.2, 0.3, 0.5 for PS and 0.025, 0.05, and 0.1 g COD/g VS.d for digested sludge respectively.

9 217 [ml] 600 COD-specific gas production ml CH4/g CODin Tss-spec.gas production ml CH4/g TSSin. 500 VSS-spec. Gas production ml CH4/g VSSin. Total specific gas production ml CH4/L Substrat in RW/pellets SLR 0,2 RW/pellets SLR 0,3 RW/pellets SLR 0,5 PW/pellets SLR 0,2 PW/pellets SLR 0,3 PW/pellets SLR 0,5 RW/DS SLR 0,025 RW/DS SLR 0,05 RW/DS SLR 0,1 PW/DS SLR 0,025 PW/DS SLR 0,05 PW/DS SLR 0,1 Figure 5: Specific CH 4 -Gas production from different substrate at different SLRs. Table 4 illustrates the actual obtained total sludge bio-activity (g COD removed /g VS.d) for raw and pre-settled wastewater as well as for acetate with granular and digested sludge compared to the initial sludge loading rates (g COD/g VS.d). Table 4: Actual sludge bio-activity obtained from ABTs. Substrate Acetate Raw wastewater initial SLR Granular sludge Digested sludge Actual sludge bioactivity Initial SLR Actual sludge bioactivity Pre-settled wastewater g COD/g Vs.d g CODrem/g VS.d g COD/g VS.d , ,05 0, ,1 g CODrem/g VS.d Also a comparison between the accumulated COD removed from the raw wastewater and pre-settled wastewater inoculated and incubated with granular and digested sludge

10 218 are measured and accumulated total CH 4 -COD removal efficiencies are calculated as shown in Figures 6 and 7. Acumulated Total CODrem. (%) Time (hrs) PW/ DS- SLR 0,025 PW/ DS- SLR 0,05 PW/ DS- SLR 0,1 PW/ PS- SLR 0,2 PW/ PS- SLR 0,3 PW/ PS- SLR 0,5 Figure 6: Accumulated CH 4 -COD removal efficiency for pre-settled wastewater. Acumulated Total CODrem. (%) Time (hrs) RW/ DS- SLR 0,025 RW/ DS- SLR 0,05 RW/ DS- SLR 0,1 RW/ PS- SLR 0,2 RW/ PS- SLR 0,3 RW/ PS- SLR 0,5 Figure 7: Accumulated CH4-COD removal efficiency for raw wastewater.

11 219 The overall results and comparison between the sludge bioactivity calculated based on TTC-test and ABTs gave that, both of TTC and ABT indicated that raw and pre-settled wastewater stimulates the increment of the biochemical activity of sludge whether digested or granular but with different values. Therefore TTC-test can be considered as a pre-test to predict the anaerobic biodegradability of substrates. Then according to positive results from TCC-test, ABTs are decided to be performed. CONCLUSION In this study the ABT was applied successfully as a helpful low cost technique for evaluating anaerobic biodegradation and for determination of the anaerobic biodegradation of domestic wastewater inoculated with digested and granular sludge. Also effect of HRT, SLR, sludge bioactivity, and biogas production were determined. The study proved that TTC test can be used as a simple test prior to decision of ABT performing, to determine the biochemical activity of sludge and also the relative change of that activity due to wastewater compounds. References: 1- APHA, (1998) American Public Health Association, standard methods for the examination of water and wastewater, 20 th edition. American Public Health Association, Washington. 2- Buitron, G. and Moreno, G. (1997) Influence of S o /X o ratio on anaerobic activity test. Wat. Sci., Technol., 40, 8, German Buitron (2002) Some factors that influence the biodegradability test results. Proceeding of Workshop on Harmionisation of anaerobic Biodegradation, activity and inhibitation assays, European Commission (Joint Research Center). 4- Haandel, A.C. van and Lettinga, G. (1994). Anaerobic sewage treatment, a practical guide for region with a hot climate. In: John Wiley & Sons, Chichester, England, ISBN Ruiz, I. M. Soto et al (1998) Performance of and biomass characterization in a UASB reactor treating domestic wastewater at ambient temperature, Water SA Vol. 24 No Jörg, R. (2001) Testverfahren zur anaeroben biologischen Abbaubarkeit, Springer Verlag, Heidelberg, pp Lettinga, G. et al. (1993) Anaerobic treatment of domestic sewage and wastewater. Wat. Sci. Tech., 27, 9, Ghangrekar, M. M. (2003): Performance and low cost potency of anaerobic sewage treatment. Proceeding of the 9 th IWA Specialised conference Design, Operation and economics of large wastewater treatment plants, pp Quezada, M., Linares I., Y. Buitron, G. (2000) Use of sequencing batch biofilter for the degradation of azo dyes (acidsand basics). Water Science and Technology, 42, 5-6,

12 VDI Guidelines (4630), March (2003) of anaerobic batch tests (Batch-Gärtest, Arbeitspapier. 11- Stergar, V. and Zagorc Koncan, J. (2002) The determination of anaerobic biodegradability of pharmaceutical waste using advanced bioassay technique. Chem. Biochem. Eng. Q. 16 (1) Zabranska, J., Jenicek, P., and Dohanyos, M., (1994) Wat. Sci. Technol. 30, 3, 103.