1 8 Laboratory procedures and methods for characterisation of faecal sludge Konstantina Velkushanova Merlien Reddy Thabiso Zikalala Bhekumuzi Gumbi Colleen Archer Barbara J. Ward Nienke Andriessen Stanley Sam Linda Strande OBJECTIVES The objectives of this chapter are to: To provide methods for protecting health and safety during collection, handling, DISCLAIMER: In this book, brand names, suppliers, and transportation, storage, and disposal of faecal manufacturer’s information are for illustration purposes sludge. only, and no endorsement is implied. Equivalent results can be achieved with apparatus and materials other than those To provide information required to adapt and presented here. Meeting the performance requirements of the develop standard methods for faecal sludge particular method is the responsibility of the sampling team characterisation, including quality assurance and laboratory. Such examples in this chapter are noted with the symbol D. and quality control (QA/QC) strategies and selection of appropriate methods. © 2021 Konstantina Velkushanova. Methods for Faecal To provide an overview of existing methods Sludge Analysis. Edited by Velkushanova K., Strande L., for faecal sludge analysis being used in partner Ronteltap M., Koottatep T., Brdjanovic D. and Buckley C. laboratories. ISBN: 9781780409115. Published by IWA Publishing, London, UK. 236 8.1 INTRODUCTION faecal sludge samples may require different preparation steps before characterisation, compared Faecal sludge management is a relatively new and with the sample preparation described in existing rapidly developing field. There is a need for increased standard methods for other matrices. Sludge with scientific knowledge and understanding of faecal higher TS concentrations may require additional sludge characteristics. To help fill this gap, standard preparation techniques such as mixing, blending, methods that can be used in scientific research and diluting, centrifuging and filtering. For example, the monitoring of treatment plants are needed. However, method for characterising the pH of faecal sludge the characterisation of faecal sludge is challenging due involves sample preparation techniques from the soil to the high variability and wide range of standard methods for high TS samples, techniques characteristics, as presented in Chapter 1, which from food science for semi-solid samples, and requires rigorous sampling methods, quality assurance techniques from wastewater methods for slurry and and quality control (QA/QC) measures, and well- liquid samples. For liquid sample matrices such as defined procedures to reduce the uncertainties in data treatment plant effluent, established standard methods generation and analysis. When using existing standard for wastewater analysis should be applicable. methods developed for other sample matrices, these methods need to be validated and adapted for the Common concerns when adapting existing specific type of faecal sludge being analysed. methods for faecal sludge include homogenisation, Presented in this chapter are examples of how dilutions, sample size, and filtration. Homogenisation laboratories are adapting existing standard methods needs special attention in order to obtain and manufacturers’ test kits for this difficult matrix, representative samples, and as discussed in Chapter 3, and also developing new methods. sampling plans need to be carefully designed and executed to produce repeatable results. Filter pore size When adapting existing methods for faecal sludge, needs to be adjusted to address issues with clogging. appropriate methods for more liquid matrices (e.g. Special pre-treatment steps such as treatment with from wastewater) or more solid matrices (e.g. from activated carbon may be required when employing fresh faeces, soil and food science) need to be colorimetric methods to ensure the inherent colour of selected. As explained in Chapter 2, four types of the sample matrix does not influence the faecal sludge are defined in this book as liquid (< 5% measurement. Faecal sludge in general has higher TS), slurry (5-15% TS), semi-solid (15-25% TS), and organic loads than wastewater or digested sludge, solid (> 25% TS). Due to the range of TS hence more dilutions will be required in the sample concentrations, mass concentrations in this book are preparation stage. In other cases, the analytical expressed as both weight/volume and weight/weight. measurements or the size of the sample are modified Unfortunately, it is not possible to make a hard and in order to adapt the method to faecal sludge. fast rule about when to analyse volumetrically Settleability and dewaterability methods are also (weight/volume) or gravimetrically (weight/weight), modified to reflect operational differences at faecal and in practice this has to be determined by how sludge treatment plants compared with wastewater accurately volumes of faecal sludge can be measured. treatment plants, for example, allowing for different In general, it is practical to analyse liquid and slurry settling or mixing times to match actual process samples volumetrically and semi-solid and solid conditions. For analysis of helminths, the UKZN PRG samples gravimetrically, but in reality, analysis needs laboratory found that the USEPA Ascaris method was to be done consistently, and samples can span the not giving adequate quantitative results for faecal entire range of concentrations. Whenever possible, it sludge, as it is often mixed with sand, soil and other is therefore recommended to report the density of materials, and the silica particles can be confused as samples, as this can be used to convert between helminth eggs under the microscope. To address this, concentrations, and TS analysis can be done in parallel the UKZN PRG developed a method that includes to report the results in weight/weight of a dry sample dissolving the silica particles and additional sieving - mass. Due to the wide range of TS concentrations, UKZN PRG helminth method (Method 8.8.1.4). 237 Methods for fresh faeces also need adaptation for use method for the specific sample matrix. The systematic with faecal sludge, as illustrated by the example of error is the inherent fluctuation in a method. For faecal sludge simulants in Chapter 7. example, if the same person was analysing replicates of the same sample, the variability within the results The methods presented in this chapter are the first would be used to calculate the systematic error. To step towards the development of standard methods for evaluate this, faecal sludge samples need to be analysis of faecal sludge. Additional method prepared across the range of TS that will be evaluated, development and adaptation is still required by and then spiked with known concentrations of a laboratories around the world. The TS method is the standard of the constituent to be measured, across the most complete method that is presented, as TS is one concentration range of the method. Then, each of the of the most basic and fundamental characteristics to samples is measured 10 times to calculate the report for faecal sludge and is often the source of many systematic error and precision. The second step errors. The chapter also includes a method for sand requires analysing blind samples that were prepared content, which is important to consider with faecal independently from the laboratory conducting the sludge, for example when interpreting VS to TS ratios. analysis. This means that the laboratory doing the Other categories of methods are not comprehensive, analysis does not know the concentration in advance, and are based on the experience of the partner but the known concentration is used after analysis to laboratories. For example, COD is the only method evaluate the accuracy of the method. The third step is presented for the analysis of organic content, as making minor changes to the method, such as mixing experience indicates that it is a representative time, sample size, temperature, or pH, and based on measurement and it is robust to the variability and the results, the ruggedness of the method is calculated. levels of organic loads in faecal sludge. Other methods Important quality assurance and quality control to consider include biochemical oxygen demand (QA/QC) measures to have in place for method (BOD), volatile fatty acids (VFA), total organic development are covered in Section 8.3. In addition, carbon (TOC), and biomethane potential (BMP), important components of method development and which will be included in future editions of the book. experimental procedure are covered throughout this A general overview of metal analysis is provided, but book, including setting up a laboratory (Chapter 2), only one example of a digestion. For nutrient analysis, how to develop and execute a sampling plan (chapters options of manufacturers’ kit-based methods, 3 and 5), and experimental design (Chapter 4). spectrophotometers, and titrations are presented but not for all parameters. Methods for characterising For the future, as more laboratories develop new crude fat and fibre are included, but further methods methods and adapt existing methods for the analysis for measuring other fibre fractions and crude protein of faecal sludge, collaborative testing can take place, are not yet included in this book. Throughout this where blind samples are analysed in parallel in chapter, information is provided about the standard multiple laboratories, as a step further to the methods being adapted, the extent of adaptation and establishment