Treated wastewater is one of the critical practices of sustainable water management. In Palestinian authority region different wastewater technologies are used to produce variety of effluents that are potentially suitable for different purposes. In this study, these different treated wastewater effluents were characterized chemically, biologically, and physically. Results showed that some of these effluents neither comply with Palestinian nor with other global effluent discharge guidelines. Chemical reactivity of five different treated wastewater effluents with chlorine was measured by determining their chlorine demand and total trihalomethane formation potential (TTHMFP). Results showed that different wastewater effluents chemical reactivity with chlorine and TTHMFP is not only dependent on wastewater treatment technology but also is affected by original water source from which was the water emerged. In all cases, measured THMs superseded acceptable drinking water limits. This would indicate responsibility of high percentage of cancer, hepatic and renal diseases among the local people.
In Palestinian Authority region, the only fresh water resource available is groundwater. Water is a major concern since the region is one of the poorest regions in the world in terms of water resources availability. Presently the application of wastewater treatment started to increase and be of more concern as a conventional water resource for different acceptable uses. Palestinian Water Authority (PWA) and Palestinian Standards Institute (PSI) are cooperating in establishing proper environmental levels and standards for domestic wastewater effluent and for treatment plants effluents. Enforcement of such environmental guidelines and standards is important for both protecting Palestinian environment and ensuring that public health principles are considered when reusing these treated wastewater sources.
Disinfection (mostly chlorination) is usually used in water and wastewater treatment process to inactivate pathogenic microorganisms to prevent or at least to minimize the risk of waterborne, washed, based and other related diseases [
Unfortunately, disinfection of drinking water or treated effluent with chlorine (as the most applicable disinfectant) comes with the formation of harmful carcinogenic and mutagenic disinfection by products (DBPs). The interaction of high load of organic and inorganic precursors enriches treated wastewater effluents causing the DBPs formation. THMs are the major class of DBPs and their presence is considered as an indicator for other DBPs occurrence such as haloacetic acids (HAAs) and total organic halides (TOX) [
The aim of this study is to investigate the potential formation of THMs from different wastewater treatment plant effluents using different treatment methods and technologies in Palestine. Treatment plants and treated wastewater samples will be characterized before the assessment of THMFP.
All chemicals were of analytical grade. Sodium hypochlorite solution (5%) and N,N-diethyl-p-phenylenediamine (DPD) purchased from (Sigma, catalog no. 261513). Sodium phosphate (catalog no. 5778), Sodium citrate (catalog no. 54641), EDTA (catalog no. E9884), Phenol crystals (catalog no. p 5566), Sodium nitroprusside (catalog no. 0501), Sodium hydroxide (catalog no. 30620), Sodium hypochlorite (catalog no. 48481), Potassium dichromate (catalog no. P5271), Silver sulfate (catalog no. S-7638), Potassium nitrate (catalog no. 221295), Glutamic acid (catalog no. G1252), Glucose (catalog no. 8270), Ascorbic acid (catalog no. A92902) were purchased from (Sigma Aldrich, USA). Sulfuric acid (95% - 97%, MERCK, 1.00731, Germany), Mercury (II) sulfate (Riedel-de Haen, 31013, Germany), and De-ionized water were used to prepare all solutions.
The free available chlorine was determined spectrophotometrically using HACH DR 1890 spectrophotometer. Ammonia, Chemical oxygen demand COD and nitrate were determined spectrophotometrically using UV-visible spectrophotometer (Perkin Elmer Lambda 10). Dissolved oxygen was measured using Oximeter with water bath (WTW-Inolab). Electric conductivity (EC) was measured using pH-EC-TDS meter (HI 9812, Hanna instruments). Turbidity and total suspended solids were measured using HACH DR\2010 Portable Data logging Spectrophotometer. COD, BOD, turbidity, total suspended solids and microbial counts were determined using standard procedures (APHA, 2006). The total organic carbon (TOC), inorganic carbon (IC), and total nitrogen (TN) was determined using TOC-VCPN coupled with TNM-1 module (Shimadzu Co). The Chromatographic separation of THMs was achieved using Gas chromatography mass spectroscopy (GC/MS). Wastewater samples were transferred quantitatively into a 10 mL headspace vial which was immediately sealed with a stainless steel screw cap with PTFE-lined septum. Vials were statically incubated at 95˚C for 10 minutes in a COMPIPAL auto sampler (CTC Analytics AG, Switzerland). An aliquot (1 mL) of the headspace gas was subsequently withdrawn and injected into a 6890N Agilent GC combined with 5973 Agilent MS. Separation was performed on a Varian Factor Four TM capillary column (VF-5 ms, 30 m, 0.25 mm, 0.25 µm). The column oven temperature was held at 35˚C for 5 min then ramped to 60˚C at 10˚C/min and finally ramped to 200˚C at 25˚C/min. Injections were done in a pulsed split mode (split ratio 10 after 0.05 min of injection) with injector temperature at 220˚C. The transfer line and the ion source temperatures were maintained at 280˚C and 230˚C, respectively. Selected ion mode (SIM) method was developed for four compounds (chloroform, bromodichloromethane, dibromochloromethane, bromoform) following USEPA 501 trihalomethane method. Quantification ions and method validation were performed with external standard calibration. Calibration curves in the concentration range from 2 to 100 mg/L were prepared from standard solution (Restek, Catalog # 30211).
Three wastewater treatment plants were selected to perform this study. Al-Quds University wastewater treatment plant (AQU P), which consists of a primary treatment unit (two stage primary settling basin), a secondary treatment unit (activated sludge with a hydraulic retention time of 16 - 20 h, coagulation and chlorination stages) with capacity of 50 m3/day. The secondary effluent is then filtered using sand filters before entering the ultrafiltration membrane which consists of a UF hollow fiber (HF) with 100 kD cutoff filters as pre polishing stage for the UF spiral wound with 20 kD cutoff filters. After ultrafiltration process, the effluent is filtered by activated carbon column followed by reverse osmosis, Diagram 1 shows Al-Quds wastewater treatment plant.
The Oasis hotel and resorts is the second wastewater treatment plant which is located on the south of Jericho city. Oasis WWTP (Oasis P) was built by TARMAC (1995) LTD, and started working in1998 to treat around 800 m3/day with peak flow rate around 60 L/sec and 2 cycles per day. The main operational process is the biological treatment using two bioreactors. The first one is supplied by aerators which are the key factor to maintain the living bacterial biomass for biodegradation of the organic content. Water is then pumped to the second bioreactor which is a sequencing 5-stepbatching reactor (SBR): filling, reacting, settling, decanting of clear supernatant effluent results after settling by gravity, and idle or disposal of sludge. Tertiary treated wastewater includes three sand filters. Chlorination is the final stage before going to storage tanks to kill bacteria and other potentially harmful microorganisms. Bio-oxidation system using fine bubble diffusers and dissolved oxygen control and monitoring, filtration up to the required level (115 micron) is achieved by using three layers of filtration media; basalt, quartz and anthracite followed by turbidity monitoring.
The third plant, Al-Uja WWTP (Auja P), it is located at Al-Uja village in Jericho, based on collection of grey wastewater from septic tanks followed by anaerobic pond, gravel filter as the primary filter and sand filter which contains shallow layer of stones, medium gravel, and pea gravel beneath a deep layer of sand and then constructed wet land that treats grey water in a reed bed system to reduce the organic load.
Samples from influent of all WWTPs were taken during the experiments and effluents of Osais and Al-Auja WWTPs were taken, whereas four samples from secondary activated sludge treatment stage, Ultrafiltration included both (hollow fiber and spiral wound) and reverse osmosis units of Al-Quds WWTP effluents were taken for chemical, biological and physical characteristics.
The ammonia concentration in non-chlorinated wastewater samples were measured before chlorination process. For ten brown one-liter bottles, 500 mL non filtrated wastewater samples were placed. Then chlorine solution was added with different concentration to achieve breakpoint curve. After chlorination, 30 minutes of incubation in dark place was done. The results of free available chlorine and ammonia were analyzed using HACH DR 1890.
Diagram 1. Al-Quds university wastewater treatment plant which consists of UF-HF, UF-SW. Activated carbon and RO filters with possible effluents samples sites.
Wastewater samples were taken from different wastewater treatment plants. 130 mL of each effluent is transferred to a brown glass bottle before chlorination, then excess constant chlorination were applied for each bottle. The bottles were incubated for 1, 2, 4, 8, 24, 48, 72, 96, 120 hours, respectively. During and after five days incubation period, a 5 mL sample was taken as function of time and quenched by ascorbic acid to prevent further THMs formation potential. pH was adjusted to 7 ± 0.3 using 0.1 M NaOH and 0.1 M HCl. Samples were kept under 25˚C in an incubator in the dark. Samples were preserved in the refrigerator at 4˚C for GC/MS analysis. All described experiments were conducted in triplicates.
Raw and treated wastewater samples characteristics are summarized in
According to Memorandum of understanding on guidelines and technical criteria for sewerage projects signed between Israel and PWA (World Bank, 2004) treated effluent should not exceed 20 mg/L of BOD and 30 mg/L TSS for secondary treatment. Nonetheless, these values may be lower for tertiary treatment TSS 10 mg/L and BOD 10 mg/L. In this study only RO effluents of AQU P achieved these limitations.
In wastewater that contains ammonium, breakpoint chlorination is a means of eliminating ammonium to achieve true free chlorine residual [
Chlorine demand of treated wastewater samples was the highest (1000 mg/L) for treated wastewater samples from AQU P taken from activated sludge tank (
On the other hand, less chlorine was required to satisfy the demand (
Treatment using membrane applications have more efficiency in chlorine demanding compounds [
Auja treatment plant is a simple primitive one that receives gray water. Figures 3(a)-(d) present Auja P ammonia and chlorine inverse relationship. The initial concentration of ammonium in tank 3 is approximately 75 mg/L and ends in the effluent to be 50 mg/L in the final tank, with chlorine demand around 300 mg/L in both influent and effluent. Hence, no obvious treatment and reduction in ammonium concentration is noticed in this treatment system. Pant and Mittal (2007) study showed that the smaller the concentration of ammonium in wastewater before chlorination, the more free chlorine that could be generated for a fixed dose of chlorine. This occurred in Auja tank 7 and final tank with FAC reaches to around 5 mg/L.
Some references provide a guideline stating when free residual chlorine is a 93% - 95% of total residual chlorine then breakpoints are achieved but such principles can be misleading (White et al., 1986). To assure that chlorination is beyond breakpoint, ammonium should be zero or very near to zero [
The difference in ammonium levels affects breakpoint results [
In all cases and samples the general inverse relationships between ammonium and free chlorine is well shown in Figures 1-3. Ammonium in wastewater reacts with free chlorine to generate more chloramines (or combined chlorine residual). Thus, the smaller the concentration of ammonium in wastewater treatment system prior to chlorination, the more free chlorine that could be generated for a fixed dosage of chlorine [
Variations in TTHM depend on the quantity and characteristics of organic matter, chlorine dose and contact time, pH, and temperature. Higher THMs arise from higher precursor levels, temperatures, dosage rates and reaction times [
The major THMs species in UF of AQU P are CF and BDCM. TTHMs mainly consist of CF occupies 84% and BDCM occupies 15%. Again the major THMs species in RO of AQU P are CF and BDCM (
The major THMs species in Oasis P are CF and BDCM (
Oasis P since bromide is present in water source in Jericho [
The major THMs species in Auja P are CF and BDCM (
AQU P receives large amounts of wastewater from different sources of AQU campus, including laboratories’ chemical and organic wastes and kitchens due to large population of the campus and from rain water. Oasis P has weak wastewater since amount of receiving wastewater and type is different. Oasis is a hotel that has different type of wastewater entering the treatment plant. Moreover, Auja P receives only grey water which is reflected on relatively low ammonia concentration. As a result, the breakpoint chlorine dosages and the patterns of the breakpoint curves varied among the samples from three WWTPs.
Chlorine is a non-selective oxidant and will therefore react with both organic and inorganic substances in wastewater in different degrees [
The TTHMFP from all wastewater treatments are compared and shown in
WHO regulated chloroform not to exceed 200 µg/L in drinking water, USEPA assigned 80 µg/L for TTHMs, and the European Union (EU) determined 100 µg/L for TTHMs [
[
According to the Environmental Protection Agency (EPA), trihalomethanes (THMs) are among the most dangerous chemical compounds into water supply [
Producing THM in drinking water can be avoided bya change in water disinfection strategy, people using chlorination strategy due to an economic reason, is considered to be cheaper than other known methods, and not because it is the best method. Therefore using chlorine dioxide, ozone, copper or silver ionization, hydrogen peroxide, and UV can be an alternative strategy, to avoid formation of THM in dirking water or a combination between two methods can be an excellent alternative method challenge is to remove any organic material, which can be a source to THM before chlorination. This can be done by applying reverse osmosis system, and unfortunately this process can remove the naturally occurring minerals from water, and wasting considerable amount of water during this process. If avoiding chlorination during water disinfection process is impossible, it is suggested to use multistage filtration steps using a house filter packaged with activated carbon, and C-18 silica gel, to avoid any contamination of drinking water by THM or any volatile organic compounds (VOCs) or any organic contaminants. The use of multistage filter will remove more than 97% of such toxic materials.
Trihalomethans (THM) contain bromide atom show high reactivity and lipophilicity, which affected tissue solubility and other physiological issues. Mink and co-workers [
Glutathione (GSH) is an important antioxidant in living cells. It plays a very crucial role in preventing important cellular damage by reactive species such as oxygen, peroxide, heavy metals and free radicals [
Metabolized THM through oxidation condition will lead to formation of phosgene, which is considered an extremely reactive chemical species, which can form in presence of biomaterials the following groups: carbonodithioate, carbonothioate, carbonate, carbamate and carbamothioate. The consequence of the reaction between phosgene and biomaterials, will lead to denaturation of proteins, peptides [
All the reaction performed by THM in the cell, will definitely lead to mutation of many proteins, and RNA wrong signal a cause to DNA damage, which will lead to diseases like cancer, and Newborn congenital anomalies similar to the causes registered near these sources of water where this study took place [
Scheme 1. The trihalomethanes THM reactions, the oxidations reaction can lead to formation of very dangers species (phosgene) which can react with many molecular cellular components, the reduction of THM can form very reactive radical species which can damage the biomaterials. THM can react by nucleophilic substitution reaction.
This study of water and wastewater is being carried out in selective areas where high percentage of Newborn congenital anomalies, cancer, hepatic & renal diseases cases occurred. It showed that THM can be considered as a major cause. The influence of the chlorination process to water will lead to series damage to molecular cellular component. Removal of such species and all organic compounds from water required an extra filtration step before using this water for drinking purposes or in any agricultural irrigation activity. The best way is to pass the water through reversed phase silica gel filter (C18-filter), or any other filter like activated carbon, which can capture organic materials. This step can remove all the dangerous organic components like THM from water and make it safer to use.
Authors will like to thanks Al-Quds University for helping in implementation this work.
Qurie, M., Awad, L. and Kanan, A. (2018) THMs Precursor Removal Efficiency from Different Wastewater Treatment Technologies Effluents. Journal of Water Resource and Protection, 10, 637-653. https://doi.org/10.4236/jwarp.2018.107036