Management of Coal Seam Gas (CSG) By-Product Water - wseas.us

2nd International Conference on WASTE MANAGEMENT, WATER POLLUTION, AIR POLLUTION, INDOOR CLIMATE (WWAI'08) Corfu, Greece, October 26-28, 2008

Management of Coal Seam Gas (CSG) By-Product Water: A Case Study on Spring Gully Mine Site in Queensland, Australia A. AVERINA1, M.G. RASUL2 and SHARMINA BEGUM3 College of Engineering and Built Environment Faculty of Sciences, Engineering and Health Central Queensland University Rockhampton, QLD 4702 AUSTRALIA

Abstract: - The study addresses two current issues – namely the rapid increase in Coal Seam Gas (CSG) developments and the associated by-product water productions, and also the scarcity of water as a resource in the study area of Queensland. This paper looks at site-specific ways of managing CSG by-product water (CSG water). The CSG production site investigated is located in Spring Gully. The Site’s current water management practices involve treatment of CSG water with Reverse Osmosis (RO) and release of the treated water into a creek nearby. This study discusses possible beneficial re-uses of CSG water. In particular it looks at the costs and benefits associated with reuse for potable purposes, mining processes, and irrigation/farming applications. Key-Words: - By-product water, Coal seam gas, Mining, Reuse CSG water, Reverse osmosis

1

chloramine formed fewer halogenated DBPs than chlorine [2]. Mechanical Thermal Expression (MTE), a novel non-evaporative brown coal (lignite) dewatering process, is being developed to increase the efficiency of power stations in the Latrobe Valley (Victoria, Australia). A by-product of this process is a large volume (potentially 20 giga liters per annum) product water stream. The study examines water quality requirements for reuse and disposal within the Latrobe Valley and their compatibility with MTE process water. It has been established that remediation of this water will be required and that the maintenance of environmental flows in surface waters would be the most suitable use for the remediated water [3]. Sirivedhin and Gary conducted a study that the chemical reactivity with chlorine as measured by disinfection by-product formation potential (DBPFP) is compared among samples of a wastewater effluent and surface waters. Water samples that had higher anthropogenic impacts were found to have higher overall DBPFP due primarily to higher dissolve organic carbon (DOC) concentrations. Effluent-derived organic matter (EfOM), however, was found to be less reactive with chlorine on a per DOC concentration basis. In this research, pyrolysis-GC/MS was used to establish relationship between structural features of DOC and DBPFP [5]. CSG plays a vital role now a day. Managing Director Richard Cottee has welcomed the Queensland Government's announcement of a $5 million grant for a

Introduction

The byproduct water, which once was an environmental problem, now is being reused by ranchers for irrigation, watering cattle, and as a source for drinking water for humans. Coal seam gas (CSG) is a natural gas formed as a by-product during the coalification process whereby organic matter is turned into coal. The subject of this Study addresses two current issues – namely the rapid increase in CSG developments and the associated byproduct water productions, and also the scarcity of water as a resource in the study area of Queensland. CSG is composed of methane gas, typically bound to the coal along its natural fractures and cleats. When water is removed from the coal seam, the pressure on the seam is reduced and the gas is released. Consequently, water is the primary by-product in the CSG production. The technology of CSG extraction has been discussed elsewhere [1]. The water associated with CSG production is usually high in salt content and other constituents that make it unsuitable for immediate uses. Many drinking water treatment plants are currently using alternative disinfectants to treat drinking water, with ozone, chlorine dioxide, and chloramines being the most popular. However, compared to chlorine, which has been much more widely studied, there is little information about the disinfection by-products (DBPs) that these alternative disinfectants produce. Over 200 DBPs were identified, many of which have never been reported. In comparing by-products formed by the different disinfectants, ozone, chlorine dioxide, and

ISSN: 1790-5095

169

ISBN: 978-960-474-017-8


 Conductivity testing of untreated CSG water  Conductivity testing of treated CSG water  pH testing of treated CSG water Based on the in-situ quality findings obtained and the past quality testing records (including two comprehensive lab analyses), the typical water quality of treated and untreated CSG water was derived. The CSG water collected from the wells in Spring Gully is treated by a Reverse Osmosis (RO) plant present at the Site and stored in a reservoir prior to being released into a creek close-by. The RO plant represents a 3-stage plant with a capacity of 9ML/day. The recovery rate of the RO plant is around 75%. With the plant currently operating at full capacity, the rate of good-quality permeate produced is around 6.75ML/day. Five (5) ponds are present on the Site. All five ponds were initially built as evaporation ponds. Current uses of the ponds are as follows:  Pond 1 – receives CSG water directly from the wells, the water is passed into Pond 2  Pond 2 – receives water from Pond 1, feeds into the RO plant via three (3) pumps  Pond 3 – receives the reject water from the RO plant, acts as an evaporation pond  Pond 4 – receives and stores contaminated water and wastewater  Pond5 –spare storage to accommodate for storage shortcomings of the other four ponds Water quality data for untreated and treated CSG water on Site was obtained first-hand by carrying out in-situ tests on 8 May 2008. Conductivity testing procedure for untreated CSG water as follows: 1. The probe of a digital conductivity meter was dipped into Ponds 1, 2. Time was taken for the reading to stabilize, 3. The reading was noted, 4. Steps 1 to 3 were carried out in three different nominated locations of Pond 1. The average of the readings was found and recorded, and 5. Steps 1 to 3 were repeated in two different nominated locations of Pond 2. The average of the readings was found and recorded. Conductivity testing procedure for treated CSG water was as follows: 1. A sample bottle was filled with treated CSG water (i.e. RO permeate water) 2. The probe of a digital conductivity meter was dipped into the sample 3. Time was taken for the reading to stabilize 4. The reading was recorded

feasibility study into the use of water produced from CSG extraction. ‘This is a far-sighted and timely allocation of funds to benefit all Queenslanders who use water,’ Mr Cottee said [6]. The key CSG water management options available for management of produced water include (but not limited to): (a) surface discharge; (b) underground injection; (c) impoundment with no re-use (evaporation, recharge); and (d) beneficial uses. For each option, the applicability, recognised constraints and data requirements have been briefly assessed where possible. For all options of use of CSG product water, two key factors must be known, the quality and quantity of supply. While some of the options presented may not be applicable in the short term, the aim is to present as many water use options as possible. The Site’s current water management practices involve treatment of CSG water with Reverse Osmosis (RO) and release the treated water into a creek nearby. This study focuses on costs and benefits associated with the following applications of CSG water [7]: Potable, Irrigation/ farming and Mining processes (coal washing). A quality analysis of RO-treated and untreated CSG water – including in-situ testing – was carried out. The findings were used to suggest the typical (site-specific) quality parameters for raw and treated CSG Water. CSG water quality and yields are discussed with respect to the various suggested applications of water. This paper, investigates the costs and benefits of site-specific ways of managing CSG water, focusing on beneficial CSG water re-use strategies. The Study is case-specific and relates to a particular operational CSG field in Spring Gully. As a part of this study, a threeday site visit to the Spring Gully CSG field was undertaken. It is noted that all the operational data were obtained first-hand from the operational staff working at the Site.

2

Water Quality Testing Procedures and Site Findings

Commercial production of CSG at the Site commenced in 2005, and currently there are around 110 operational wells. Operational CSG wells in Spring Gully produce between 200 barrels (31.8kL) and 3000 barrels (477kL) of water per day. It is estimated that a total of around 37,000 barrels (5,883kL = 5.9ML) of water per day is currently produced by the field.

2.1 Water Quality Testing In-situ water quality testing carried out included the following:

ISSN: 1790-5095

170

ISBN: 978-960-474-017-8


Table 1: Typical treated and untreated CSG water quality

The pH testing procedure for treated CSG water was follows: 1. A sample bottle was filled with treated CSG water (i.e. RO permeate water) 2. The probe of a digital pH meter was dipped into the sample 3. Time was taken for the reading to stabilize 4. The reading was recorded

Analyte Description pH Chloride Nitrate N (Calc) Fluoride by ISE Selenium as Se Sodium as Na Potassium as K Magnesium as Mg Total hardness as CaCO3 Iron as Fe Boron as B Barium as Ba Manganese as Mn Aluminium as Al

2.2 Typical Water Quality Typical quality parameters for the treated and untreated CSG water are presented in Table 1.

2.3 Water Quality Standards Quality standards for drinking water in Australia are set out by the Australian Drinking Water Guidelines [8]. Quality standards for other applications of water – such as irrigation and livestock – are outlined in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality [9].

2.4 Water Quality Discussion All the typical quality values of untreated and treated CSG water were compared against the drinking guidelines, irrigation guidelines and livestock guidelines. The comparison is presented in Table 2. The comparison of the typical water quality

mg/L mg/L mg/L mg/L mg/L mg/L mg/L

Untreated CSG water Average 9.2 3850