Industrial Water Reuse and Recycling, an Introduction

Abstract

This chapter provides an introduction to industrial water reuse and recycling and is interlinked with several specific chapters in this field. The major issues discussed consist of usable raw water sources, water recycling and reuse applications (including quality requirements), drivers for the realization of this management option, and key success factors such as water reuse sustainability; the true value of water; financing; process design including pilot testing, operation, and maintenance; and concentrate management.

Major sources are drought-proof municipal and industrial effluents. A special resource is RO concentrate, which can be reused, e.g., for refinery coke quenching. Another option under discussion is the reuse of reclaimed water from one company by another (e.g., in industrial parks/multicompany sites where distances between the companies are relatively short). An unusual resource is river water heavily polluted by municipal and industrial effluents. A brief case study within this context is presented.

The topics of water supply security, economic benefits including brand protection and reputational risk management, as well as government policies and the green image of companies are all addressed as main drivers. Economic benefits are obtained mainly through savings of freshwater from the public supply, lower used water discharge fees, and resource recovery. Another economic advantage that is normally omitted from feasibility studies is the increase in water supply security. As an example for the implementation of government policies, the new water reuse guideline from the Indian state of Gujarat is discussed. Green image has also been identified as an important driver, as it is increasingly part of the corporate culture of many enterprises. The related benefits derive from the fact that employees are proud of a green image and are therefore more motivated. In addition, customers are increasingly willing to pay a higher price for sustainable solutions.

The major industrial applications are recycling and the reuse of various raw water sources as cooling and boiler make-up water. Within this context, several cases of industrial effluent recycling and the reuse of municipal secondary effluents are discussed in brief. Especially, in the case of the recycling of boiler make-up water, advanced multi-barrier systems (including ultrafiltration and reverse osmosis and mixed bed ion exchange) have been employed in order to meet stringent quality requirements (e.g., for silica) and subsequently to guarantee the power supply for industrial processes such as petrochemical manufacturing. With this in view, it is also very important that the reclamation plants are operated and monitored by well-trained and skilled personnel from the plant owner or a water technology specialist. Another success factor is suitable design, which in many cases is based on pilot tests. Design examples including reuse targets are described (e.g., a UF design comparison for three different reuse applications). Another important topic is concentrate management, which is discussed on the basis of disposal and beneficial reuse (including zero liquid discharge) cases. Apart from technological and operational issues, financing (e.g., public-private partnership/PPP) is addressed, which is very important for the realization of water reuse projects, especially in developing countries. Finally, the overriding importance of sustainability as a key success factor is emphasized and the conclusion drawn that water reuse and recycling solutions have to be ecologically, economically, and socially sustainable in order to provide benefits to all the stakeholders involved.

Introduction

If the degradation of the natural environment and the unsustainable pressure on global water resources continue at current rates, 45% of global gross domestic product will be at risk by 2050 (United Nations 2019). One of the sustainable options that facilitate the avoidance of this risk is water reuse. Agriculture is by far the largest water consumer (69% of the global water withdrawals). Industry (including power generation) accounts for 19% and the municipal sector for 12% (AQUASTAT 2016).

In order to provide an indication of industrial water demand in different regions, figures from the USA as a highly developed nation, the heavily industrialized city-state of Singapore, and Windhoek, the capital city of Namibia, which is a developing country, are presented.

In the USA, the largest water user is thermoelectric power generation for domestic and industrial supply (U.S. Geological Survey/USGS 2015). In 2015, thermoelectric power generation used 503 million m³ per day (41% of total water use) of fresh and saline water and was followed by irrigation, which employed 447 million m³ per day (37% of total water use). However, it must be pointed out that the two figures are not really comparable, as in the first case (thermoelectric power generation), the water is only partly lost (due to evaporation in the turbine and cooling tower), and most of it can be reused, while in the second case (irrigation), use is consumptive (100% is lost owing to crop uptake, evaporation, and trickling into the soil). The major reason for the high water consumption in thermoelectric power generation can be explained by the fact that at present, inefficient once-through cooling tower systems are still employed. However, it has to be mentioned that between 2010 and 2015, cooling water consumption fell by 18% and that there is a strong, positive trend with regard to efficiency (achieved by cooling water circulation). Total water use (87% freshwater and 13% saline water withdrawal) amounted to 1.219 billion m³ per day in 2015. As compared to 2010, this represented a reduction of 9%. Commercial and industrial demand amounted to approximately 114 million m³ per day (self-abstraction and public supply in 2015), while domestic use totaled 101 million m³ per day (public supply and self-supplied withdrawals in 2015). Thus, (countrywide average) commercial and industrial water consumption (without thermoelectric power generation) stood at 9%, which was slightly higher than the domestic figure (8%; also excluding thermoelectric power generation).

As mentioned above, water consumption in the USA is decreasing. The major reasons for this are cooling water circuit closing, conservation measures, and water reclamation and reuse. Water reuse is gaining in importance especially in water-stressed states. For example, in California, a survey published in 2009 indicated that the total use of recycled water had increased from 1.8 million m³ per day to 2.3 million m³ per day (28%) in the last decade, while the amount of recycled water used for industrial purposes had practically doubled (from 44,000 to more than 88,000 m³ per day) (Rosenblum et al. 2012). In Florida, industrial water reuse (16% of total water reuse) increased from 330,000 m³/d in 2010 to more than 430,000 m³ in 2011 (32%).

In Singapore, which is a heavily industrialized city-state, the current share of the non-domestic water demand is 55%, which corresponds with a supply of 1.06 million m³ per day to commercial enterprises and industry (Seah 2018). It is predicted that the current total water demand of 1.94 million m³ per day will double to 3.88 million m³ per day by 2060 with a substantial shift from domestic water to non-domestic water, which will rise from 55% to 70% (accordingly the share of domestic water will decline from 45% to 30%). This would mean a tremendous increase in non-domestic water demand (from 1.06 million m³ per day in 2018 to 2.7 million m³ per day in 2060). Therefore, non-domestic water demand management represents the main focus of efforts aimed at achieving greater water sustainability in Singapore. In order to attain this objective, the Singaporean Public Utilities Board (PUB) has developed the so-called 3Rs Water Efficient Strategy (Seah 2018) for the non-domestic sector. The three “Rs” stand for reduce (water efficiency measures), replace (surface and imported water to be replaced by NEWater and desalinated water), and reclaim (water reclamation from “trade effluents,” i.e., commercial and industrial effluents).

Within this context, it should be mentioned that Singapore has four national sources: surface water, imported water from Malaysia, desalinated seawater, and NEWater (reclaimed water from municipal effluents; Fig. 1). At present, NEWater can meet up to 40% of total water demand and is mainly reused in industry (>90%; major users are the electronics, chemicals, refining, and petrochemical industries). The rest (<10%) is reused for potable purposes (indirect potable reuse, IPR). As far as the water supply from Malaysia is concerned (up to 1.14 million m³ per day from Johor River), there is currently a price dispute. Malaysia wants to renegotiate the water supply agreement concluded in 1962 and has threatened to seek international arbitration if Singapore refuses (Global Water Intelligence 2019a). It can be assumed that this dispute will lead to an intensification of Singapore’s efforts to become independent by increasing the production of own sources (reclaimed and desalinated seawater).

Fig. 1

NEWater tank at Bedok, Singapore. (© WABAG)

The aforementioned figures show that today, industry is already using reclaimed water (NEWater) to a relatively large extent. In future, NEWater production capacity (apart from desalinated seawater, which however is relatively expensive) will be further increased (to 55% in 2060) in order to cover rising industrial demand. It may be assumed that for various reasons, on-site water reuse and recycling will also be substantially increased, as they reduce environmental impact and in some cases cut costs (NEWater costs are higher) due to short distance conveyance and lower quality requirements for certain applications and because the effluents are already owned by the industry generating/discharging them.

Windhoek is the capital city of Namibia, which is a developing country. Windhoek’s total water demand in 2016 was 26.44 million m³ per annum (van Rensburg 2019) and consisted of 60% domestic (15.86 million m³ per annum) and 40% non-domestic (10.57 million m³ per annum) consumption. In turn, non-domestic water consumption (40% of total water demand) was split between commercial and institutional users (28%) and industry (12%). The main industrial enterprises are food and beverage companies, an abattoir, and a tannery. The industrial effluents are treated in a central water reclamation plant (Fig. 2) and at present are reused mainly for river water augmentation and dust control in road construction (see chapter “Windhoek/Ujams Industrial Water Reclamation Plant, Case Study Namibia”). Due to increasing water stress (caused largely by population growth and more frequent droughts), the reuse after further treatment (partial desalination) of reclaimed water by the aforementioned and other industries is being considered. The sources for the domestic supply (60% of the total water consumption) are treated dam water, borehole water, and reclaimed water from the New Goreangab Water Reclamation Plant (see chapter “Windhoek/Goreangab Direct Potable Water Reuse, Case Study Namibia”).

Fig. 2

Ujams Water Reclamation Plant. (© WABAG)

Reclaimed Water Quality Issues

Specific quality issues vary among industries. Major water quality issues are associated with the prevention of corrosion, scaling, and biological fouling. Design and reclaimed water quality issues are addressed and discussed mainly in the sections Water reuse and recycling applications and Key Success Factors for Water Recycling and Reuse, as well as in the interlinked chapters on the basis of case studies.

Industrial Water Reuse and Recycling Sources

Industrial water recycling can be defined as the in-house/internal reuse of used water (UW; in-house/internal process effluents) within the industrial unit producing the effluents. Industrial water reuse can be divided into the reuse of external sources (mainly water reclaimed from municipal secondary and tertiary effluents) and the reuse of internal sources emanating from one process unit to another. Which of these options is the most feasible depends upon several factors such as water management policy and legislation, price policy (e.g., price of freshwater from municipal networks), the hydrological situation (degree of water stress), the availability of proper recipients, pollutant concentrations in the reclamation plant inlet, recycling/reuse applications and the distance to the user (conveyance cost), etc.

The simplest form of industrial water reuse is cascading. This represents water reuse without water reclamation, i.e., the untreated used water from a process unit is reused in another process unit with lower quality requirements, and this procedure is then repeated in further process units. The used water from the last cascading unit is either treated in a water reclamation plant (WRP) for further reuse or in an effluent treatment plant (ETP) for discharge into the municipal sewerage system or a recipient. For example, this practice is employed by the pulp and paper industry.

Figure 3 represents water recycling. Effluents from the production facilities are treated in an ETP and reclaimed in a WRP for recycling in the production facilities. This is an ideal case of water recycling. Normally, both water recycling and water reuse are practiced simultaneously. One example of this hybrid configuration is shown in Fig. 4. In this case, the production facility effluents are also treated by an ETP and reclaimed by a WRP. Part of the purified ETP effluent is reused in other production facilities or for non-production purposes such as irrigation or firefighting. The reclaimed water is recycled to the production facilities and reused as boiler and cooling tower make-up. The cooling tower and boiler blowdowns, as well as ion exchange regenerates (from boiler make-up water polishing), are recycled after reclamation in the WRP together with the ETP effluent.

Fig. 3

Industrial water recycling. (© WABAG)

Fig. 4

Industrial water recycling and reuse. (© WABAG)

In the Panipat Refinery WRP, for example, secondary effluents, cooling tower, and boiler blowdowns, as well as petrochemical effluents, are recycled and reused as boiler make-up and as process water for petrochemical production (see chapter “Panipat Refinery Water Reclamation Plant, Case Study India” and Lahnsteiner and Mittal 2010; Lahnsteiner et al. 2013). The RO concentrates from WRPs can also be reused, e.g., for refinery coke quenching (see chapter “Panipat Refinery Water Reclamation Plant, Case Study India”) or dust suppression in ash handling (see chapter “Angul Jindal Steel and Power Coal Gasification Water Reclamation Plant, Case Study India”).

Municipal used water is another (drought-proof) source for industrial reuse (Fig. 5). Secondary effluent is treated in water reclamation plants and distributed to various industrial users (see chapter “Advanced Treatment of Municipal Secondary Effluents and Reuse of High-Quality Water in a Refinery and the Automotive Industry, Case Study Chennai/India”).

Fig. 5

Industrial water reuse – source water: municipal secondary effluent. (© WABAG)

Figure 6 shows a secondary effluent reservoir, which mainly provides raw water for reclamation in an advanced multi-barrier system (with ultrafiltration and reverse osmosis as core technologies). The reclaimed water is reused in the refining and petrochemical industry as cooling and boiler make-up water (see chapter “Advanced Treatment of Municipal Secondary Effluents and Reuse of High-Quality Water in a Refinery and the Automotive Industry, Case Study Chennai/India”).

Fig. 6

Secondary effluent reservoir for reclamation and reuse in the refining and petrochemical industry – Chennai, India. (© WABAG)

In many cases, industry has to use both resources (in-house effluents and secondary/tertiary municipal effluents) and additionally desalinated seawater (if located on the sea) if no other sources (ground and surface water) are available. This is especially true during droughts, when drinking water demand cannot be met and the authorities first cut off the water supplied to industry from the public network. Another option that is under discussion is the reuse of reclaimed water from one industry (or from an industry park) to another (e.g., the employment of treated used water from a beverage company in another branch such as a pulp and paper or steel making).

Finally in this section, an unusual source of industrial water reuse should be mentioned. This is polluted river water as exemplified by the Yamuna River in Delhi, which is severely polluted (COD = 140 mg/L, BOD = 60 mg/L, TOC = 43 mg/L, total Kjeldahl nitrogen = 25 mg/L, bacteria 5 × 10⁶ CFU) owing to discharges of municipal and industrial used water and its use as a source for the 3 × 95 MW & 2 × 210 MW Badarpur thermal power stations (owned by the National Thermal Power Corporation Ltd., NTPC, Delhi). The pretreated (clarified) raw water is cleaned to a high degree by means of a combination of MBR (submerged hollow fiber membranes; Fig. 7) and reverse osmosis (Q = 3000 m³/day) and can thus be employed as feedwater for the demineralization unit (ion exchange) and the subsequent production of boiler feedwater. The major target values for the MBR permeate are BOD <5 mg/L, total nitrogen <10 mg N/L, SDI ≤ 3, and turbidity ≤0.5 NTU and TDS < 150 mg/L for the RO permeate (further TDS removal by ion exchange at the power plant). The plant was commissioned in 2015, and analogue to Defacto Potable Water Reuse, this application could be called “Defacto Industrial Water Reuse.”

Fig. 7

NTPC/Badarpur-MBR for the reclamation of polluted river water. (© WABAG)

Drivers for Industrial Water Recycling and Reuse

The major drivers for industrial water recycling and reuse are economic and include the boost to water supply reliability. Government policies (e.g., regional development based on water sustainability increase) and regulations, brand protection, and reputational risk minimization, as well as the “green image” of industrial enterprises, constitute other significant drivers.

Economic benefits are obtained mainly through savings of freshwater from the public supply, lower used water discharge fees, and resource recovery. Another economic advantage that is generally omitted from feasibility studies is the increase in water supply security (i.e., the risk avoided is not evaluated). Production downtimes, e.g., in a refinery, can cause financial losses that in a relatively short time may well exceed the contractual value of the entire water reclamation plant. Further damage might also emanate from the loss of reputation and client trust. Therefore, the safe provision of (high quality/safe) water is an essential element in industrial production, as it provides secured earnings, brand protection, and reputational risk management.

Within the context of government policies, one current example in this regard is the published Gujarat State “Reuse of Treated Waste Water Policy” in India (Vishwa Mohan 2018). Due to the lack of sufficient water from perennial rivers, declining groundwater levels, and seawater intrusion, Gujarat can be considered as severely water-stressed. Regular droughts aggravate this situation. In line with the aforementioned policy, it is planned to create a reclaimed water grid, similar to a power grid. The raw water source is comprised of municipal used water from more than 150 municipalities. The reclaimed water (tertiary effluent: TSS < 10 mg/L) is to be reused (after tertiary treatment) mainly in industry in order to save freshwater (raw water/river water from the Gujarat State water supply as well as groundwater). The rate for the reclaimed water has to be cheaper than the traditional sources (surface and groundwater) in order to account/compensate for its poorer quality (as compared to freshwater) and provide an incentive for water reuse. The vision as part of the policy is the collection and treatment of generated sewage, the reuse of the reclaimed water on a sustainable basis, and a subsequent reduction in freshwater resource dependency. In addition, the promotion of the reclaimed water as an economic resource is envisaged (i.e., environmental protection, increasing water supply security, and value creation from used water).

A bill (Californian SB 332) introduced in February 2019, would accelerate the adoption of water reuse initiatives in California. The proposed legislation aims to slash the volume of treated municipal used water discharged into the Pacific Ocean. It would require all used water treatment plants discharging via an ocean outfall to cut their discharge by at least 50% by 2030 and 95% by 2040 (Global Water Intelligence 2019b). If passed into legislation, the reclaimed water would be used as drought-proof source water for all kinds of reuse applications and enhance overall water supply security. There are also water reuse initiatives in Europe. One of them is the Portuguese water reuse initiative launched on 22 March 2019 (GWI 2019c). This has been designed to address decreasing rainfall and rising water demand while meeting the government’s commitment to circular economic development. The initiative aims to reclaim and reuse 10% of the effluents generated by the 50 largest municipal used water treatment plants by 2025 and 20% by 2030. The capital city of Lisbon has given a commitment that by 2030, it will source 25% of its total water needs from reclaimed water, which will be reused mainly for urban and industrial purposes.

As far as green image is concerned, it has to be said that environmental sustainability is now part of the corporate culture of many enterprises. The related benefits derive from the fact that employees are proud of a green image and are therefore more motivated (Rosenblum 2012). In addition, customers are increasingly willing to pay a higher price for sustainable solutions.

Industrial Water Recycling and Reuse Applications

The major industrial application consuming the largest quantities of water is thermal power generation, i.e., cooling (see chapter “Cooling Water Treatment”) and steam generation (see chapter “Boiler Make-up Water Treatment”). Cooling and boiler make-up water reclamation requires adequate pretreatment (e.g., by dissolved air flotation, solid contact clarification, and dual media filtration; Figs. 8 and 9) and a desalination process, which is usually carried out using ion exchange filters (of various designs), reverse osmosis (Fig. 10) in combination with polishing ion exchangers (mixed bed filters), or electrodeionization (EDI). In many cases (e.g. at the Essar Refinery, Lahnsteiner et al. 2015), RO pass I permeate is employed as cooling make-up (Fig. 8) and pass II permeate as boiler make-up (after polishing in mixed bed ion exchangers, Fig. 8). The major objective in boiler make-up water treatment is to avoid corrosion and the formation of deposits. In this connection, the most important quality parameters are pH, conductivity, total dissolved solids, and silica, which depending upon the boiler type has to be removed below the stringent value of 0.01 mg/L (after polishing by mixed bed ion exchange). The main problems in cooling circuits are biological growth (including Legionella bacteria), biofouling, corrosion, and scale deposits. Accordingly, typical treatment consists of coagulation/flocculation, lime softening, sedimentation, filtration and disinfection, or alternatively, as previously mentioned, reverse osmosis with appropriate pretreatment and disinfection. The quality requirements relate to the materials (galvanized steel, stainless steel, copper, etc.) used in the cooling tower. For galvanized steel, e.g., the recommended limit for chloride is 500 ppm and for copper 0.5 ppm, and the pH should be in the range of 6–9 (Puckorius 2018). In the design of new cooling towers, it is also possible to adapt the type and quality of the materials (for the cooling tower, piping, and heat exchanger tubing) to that of the reclaimed water.

Fig. 8

Essar Refinery Water Reclamation Plant – simplified process flow diagram. (© WABAG)

Fig. 9

Essar Refinery Water Reclamation Plant – solid contact clarifier. (© WABAG)

Fig. 10

Essar Refinery Water Reclamation Plant – reverse osmosis unit. (© WABAG)

An example of cooling water reclaimed from municipal secondary effluent is shown in Fig. 11. This represents the process flow diagram of the Baotou water reclamation and cooling make-up reuse application (Lahnsteiner et al. 2007). Baotou is the largest industrial city in the autonomous province of Inner Mongolia. Annual precipitation in Baotou amounts to approximately 300 mm, and therefore, due to high levels of industrialization and a low level of natural water resource renewal, water reuse is a major priority in the city. In order to comply with national water conservation policy (National Development and Reform Commission 2005), as well as to save costs for freshwater from the municipal network, the Baotou Donghua Power Plant is reusing reclaimed municipal secondary effluent as make-up water for its cooling water circuit.

Fig. 11

Baotou water reclamation and reuse scheme. (© WABAG)

The water reclamation plant consists of coagulation, flocculation, lamella sedimentation, and biological aerated filters (BAF, biofiltration; see chapter “Biofiltration/Biological Aerated Filters in Municipal Used Water Treatment”) and is located on the site of the Baotou Donghedong UWTP. The raw water consists of secondary effluent from the Baotou Donghedong (Donghe East) and the Baotou Donghexi (Donghe West) municipal used water treatment facilities. The reclaimed water has to meet the quality requirements for the reuse of secondary effluents as make-up water for cooling water circuits laid down by the “Code for the design of wastewater reclamation and reuse GB/T50335-2016” (major parameters: pH 6.5–8.5, turbidity ≤5 NTU, BOD₅ ≤ 10 mg/L, COD ≤60 mg/L, Fe²⁺ ≤ 0.3 mg/L, Mn²⁺ ≤ 0.1 mg/L, Cl⁻ ≤ 250 mg/L, SiO₂ ≤ 50 mg/L, total hardness ≤450 mg/L CaCO₃, NH₄-N ≤ 10 mg/L, total phosphorous ≤1 mg/L, TDS ≤ 1000 mg/L, residual chlorine ≥0.5, fecal coliforms ≤2000) (Code of China 2016).

The secondary effluent is pretreated by coagulation with aluminum chloride and static in-line mixers, flocculation, polymer dosing, and lamella sedimentation. The main process step is biofiltration (BAF, BIOPUR-NK; Fig. 12), which employs granular carrier material (expanded clay), upflow operation, and excess head backwashing, in order to minimize filter media losses. The main advantages of biofiltration consist of reduced space requirements and high process stability. The main reason for choosing compact BAF technology as a tertiary treatment step was the rather limited land available at the Donghedong UWTP. The major purpose of the BAF process step is nitrification.

Fig. 12

Biofilter (BAF, BIOPUR-NK) during backwashing. (© WABAG)

The removal of ammonium by nitrification is necessary, as it is a nutrient, which promotes microbiological growth in the power plant’s heat exchanger and the cooling tower fill (Loretitsch and Puckorius 2005). In addition, ammonium can corrode the copper alloys used in heat exchangers (by forming a tetraammincopper(II) complex). Another advantage of nitrification is that alkalinity is decreased significantly, thus reducing the acid requirement for pH control. Furthermore, a positive side effect of nitrification is provided by the nitrate produced, which along with phosphate acts as a mild corrosion inhibitor. Apart from nitrification a degree of suspended solid and carbonaceous compound (COD, BOD₅) removal is accomplished in the BAF. This organic carbon reduction can be beneficial within the context of biofouling control (reduced biocide demand) in the cooling water circuit.

The make-up water treatment at the power plant consists of lime softening, flocculation/precipitation with ferric chloride, and sand filtration. Sulfuric acid is added for pH adjustment. Chlorine dioxide and an anti-scalant are dosed into the make-up water for circuit water conditioning.

In general, it can be stated that the reuse of secondary effluent as cooling make-up water is a very beneficial application, as large quantities of relatively low-quality water are required for cooling purposes. Moreover, this practice is sustainable, as substantial amounts of freshwater (from the public network) can be saved. This is of great importance due to the fact that groundwater levels in Inner Mongolia have declined markedly in recent decades and that the flow of Yellow River, which is located some 10 km south of the power plant, has decreased rapidly (Fig. 13), causing the river to dry up regularly in the downstream regions (Shandong Province) of eastern China.

Fig. 13

Yellow River/Huang He at Baotou, Inner Mongolia, China. (© WABAG)

Other applications (apart from cooling tower and boiler make-up water reuse) include recycling and reuse in diverse manufacturing processes such as polymerization/polycondensation, bleaching, dyeing, transport, washing, quenching, and maintaining pressure. These are employed in chemicals production, pulp and paper manufacturing, textile production, mining, steelmaking, oil exploration and refining, etc. In the Panipat Refinery, the high-quality reclaimed water (TDS < 0.1 mg/L, Silica < 0.01 mg/L) is reused in purified terephthalic acid manufacturing (PTA) and thermal power generation (see chapter “Panipat Refinery Water Reclamation Plant, Case Study India”).

In the Petrobrazi Refinery in Romania, the reclaimed water is reused as service water. The conventional used water treatment plant consists basically of oil removal by API and DAF separation and biological treatment. For water reclamation, 40% of the secondary effluent is treated in a cartridge filter station and reused in the firefighting system and for quenching refinery coke (see chapter “Petrobrazi Refinery Used Water Treatment Plant, Case Study Romania”).

In El Segundo/California, the West Basin Municipal Water District produces five types of so-called designer waters in its famous Edward C. Little Water Recycling Facility (Q = 150,000 m³/day). The five types of these “tailor-made to customer needs” water qualities include tertiary Title 22 water for a wide range of industrial and irrigation purposes, nitrified water for industrial cooling tower make-up water production, disinfected RO permeate for groundwater recharge (seawater intrusion barrier), “pure” RO permeate (single-pass RO) for refinery low-pressure boiler feedwater, and “ultra-pure” RO permeate (two passes RO) for refinery high-pressure boiler feedwater production (West Basin Municipal Water District 2019; Fuchs 2017).

A relatively new topic is water reuse in (hyper scale) data centers (operated by Microsoft and other IT companies) as water cooling requires less energy than air cooling (Lesniak 2017). Data centers are a growing segment and are needed increasingly for video streaming, artificial intelligence, machine learning, cloud computing, mobile devices, augmented reality, the Internet-of-Tools, GPS, etc. The motivation for water reuse can simply be OPEX reduction or more strategically the achievement of corporate water and energy sustainability goals (e.g., a 25% reduction in water withdrawal and a 10% reduction in greenhouse gas emissions). The incentives may consist of brand protection and reputational risk minimization, as water can be a constraint upon growth. Furthermore, the water footprint as a measure for sustainability is gaining in importance for listed companies, as it is of relevance to the performance of shares on stock exchanges. In San Antonio, California, on the basis of an innovative and risk-minimizing solution, Microsoft has invested in reusing reclaimed water from the San Antonio water system for its cooling demands, and risk-adjusted OPEX savings of US$ 1.2 million per year have been documented. Apart from OPEX reduction, the goals are the maintenance or surpassing of sustainability targets, speed to market targets, and the meeting of water safety standards (Lesniak 2017).

Key Success Factors for Industrial Water Recycling and Reuse

Sustainable Solutions

First and foremost, water recycling and reuse solutions have to be sustainable, and this presupposes economic, technological, and social sustainability. Moreover, economic sustainability should not only mean short payback periods of 3–5 years. In fact, industry must accept longer return on investment periods (at least 10 years) in order to promote water reuse and overall sustainability that includes industrial, agricultural, urban, and potable water supply reliability, which is also of great social relevance. Social sustainability is important, especially in developing countries and emerging markets, and incorporates the creation of jobs and subsequent improvements in the health situation and the overall standard of living.

The True Value of Water

The risks avoided by higher water supply reliability should be valued in feasibility studies. A shutdown of an industrial facility can cause major revenue losses. One example in this connection is a refinery and petrochemical complex (R&PC) operated at Dahej in northwestern India. Dahej is located in the Gujarat State between the Gulf of Khambhat (an inlet of the Arabian Sea) and the sacred Narmada River. Annual rainfall is less than 500 mm of which more than 80 per cent occurs during the monsoon months of July to September. Owing to the lack of sufficient water from perennial rivers, declining groundwater levels, and seawater intrusion, the region can be considered as water-stressed. Regular droughts exacerbate this situation, and in May 2016, Reliance Industries Limited (RIL) had to shut down the refinery and petrochemical complex for several days due to one of severest water shortages ever. This drought lowered the flow of the Narmada River, which became brackish during high tides and was therefore unsuitable for industrial water production. In order to cope with this problem, RO permeate from the Reliance Jamnagar refinery and petrochemical complex was shipped to Dahej, while with a view to solving the problem of future droughts (expected every year before the monsoon season), VA TECH WABAG India was commissioned with the construction of a 50,000 m³/day Narmada River brackish water RO (with UF as a pretreatment step), which was completed in the record time of only 8 months. The R&PC’s water management is based mainly on the use of Narmada River and recycled water, and in order to meet the overall demand for industrial water, water recycling must be increased and desalinated seawater employed. Within this context, a desalination plant (SWRO; 100,000 m³/day) is to be built (in two phases) in order to secure a reliable water supply for the entire Dahej special economic zone.

In order to assess scenarios like the above, the so-called Water Risk Monetizer has been developed by Ecolab in partnership with Trucost and Microsoft (www.WaterRiskMonetizer.com). This modeling tool helps businesses to incorporate water risks into business decisions and planning, i.e., to understand the full value of water to the business, calculate the potential revenue at risk, and quantify water risks in financial terms (Lesniak 2017).

Financing

As a rule, industrial water reclamation plants are self-financed by industrial enterprises and are largely dependent upon economic feasibility. In highly water-stressed regions, industrial supply can be endangered during droughts by public supplier cuts, as the potable water supply always has priority over the industrial supply. In such situations, it is essential to guarantee industrial water supply security through the use of alternative sources, and industries do not hesitate to invest in order to avoid shutdowns, which as previously mentioned can be very costly.

In an online (life) survey conducted during the Industrial Water Solutions Forum held on 11 July 2018 as part of the Singapore International Water Week, financial investment and return on investment (ROI) were identified as the major obstacles/challenges to water recycling initiatives (Gasson 2018). The overall result of the survey was as follows: 34% financial investment and ROI, 20% operational costs and/or man power limitations, 10% difficult water to treat, 12% lack of knowledge of available solutions, 19% site constraints, and 5% project priorities. If industry were to accept longer ROIs as the aforesaid, it may be assumed that the result of this survey (34% financial investment and ROI as major obstacle/challenge) would be different.

As mentioned previously, in data centers water cooling is cheaper than standard air cooling. However, this is not a guarantee for investment in water-cooling, as speed is the decisive factor in project realization. Data center completion is generally required in under 7 months for less than US$ 7 million per megawatt (Lesniak 2017). Anything that slows down or adds cost to a project faces significant scrutiny by executives trying to keep pace with growth. Therefore, technical water recycling issues such as waterborne pathogens (Legionella) and the need for large volumes of on-site water storage may be a significant concern and subsequently a reason for non-investment (in a water reclamation facility). Nonetheless, if innovative and risk-minimizing solutions are available, industry does invest, as demonstrated by the San Antonio (Microsoft) water recycling project.

One example of regional development financing is the Camp Tarragona water reclamation and reuse project, which was realized in order to provide nonconventional water resources (reclaimed water from municipal secondary effluents) in a water-stressed region to industrial users (a petrochemical park and a nearby power plant). The water reclamation plant and a 14 km-long distribution system were co-financed by the Catalan Water Agency, the EU Cohesion Fund, and the Spanish Ministry of the Environment. The major benefits of this project have been the provision of a locally available alternative water supply that avoids the need for water transfers from a distant source (Ebro River) and promotes industrial growth and regional sustainability (Sanz et al. 2015).

If industrial water reclamation plants are contracted by public utilities, financing via development banks and public-private partnerships (PPP) represents an option, especially in developing countries. The Ujams Water Reclamation project realized in Windhoek, Namibia, is worthy of mention as an example of PPP financing (see chapter “Windhoek/Ujams Industrial Water Reclamation Plant, Case Study Namibia”). It represents a partnership between the city of Windhoek and the private Ujams Wastewater Treatment Company Ltd. (UWTC) and is based on a BOOT business model (build, own, operate, transfer). The water reclamation plant was commissioned in 2014 (Fig. 14) and incorporates micro-sieving, MBR, and UV disinfection as core technologies. It is being operated for a period of 21 years up to 2035 by UWTC, after which it will be transferred to the city of Windhoek. The major benefits of this public-private partnership have been the relatively quick provision of reliable water infrastructure and the transfer of technology and knowledge from developed Europe to developing Africa.

Fig. 14

Ujams Water Reclamation Plant – the plaque commemorating its official inauguration on 7 October 2014. (© WABAG)

Process Design

The correct design and the professional operation and maintenance of the water reclamation plant (WRP) represent key factors in technological sustainability success. A safe and reliable design can be accomplished, as in potable water reuse (IPR and DPR), by the employment of multiple barrier systems using conventional and advanced technologies. However, first of all, efficient pretreatment has to be accomplished upstream of the WRPs. The cleaning of both single-process (hazardous) effluents such as sulfidic and naphthenic spent caustic (by e.g., wet air oxidation) and blended used water streams (normally by biological treatment) is essential. Figure 15 shows the biological pretreatment unit upstream of the Reliance Industries Limited (RIL) Jamnagar refinery and petrochemical complex DTA water reclamation plant, which basically consists of tertiary clarification, ultrafiltration (Fig. 16), and reverse osmosis.

Fig. 15

RIL Jamnagar refinery and petrochemical complex DTA WRP – biological pretreatment unit. (© WABAG)

Fig. 16

IOCL Panipat Refinery WRP – Pentair/Norit/X-Flow Xiga membrane system. (© WABAG)

In order to discuss the most relevant design issues (source water quality, pretreatment, key technologies, reuse applications, etc.), in the following section, two industrial multiple barrier systems in India (Lahnsteiner and Mittal 2010; Lahnsteiner et al. 2013) are described in brief. These are the Panipat Refinery Water Reclamation Plant for the recycling of refinery and petrochemical used water and the Chennai Petroleum Water Reclamation Plant for the reuse of municipal secondary effluent. In addition, the UF designs of these two industrial WRPs are compared with the UF in a potable water reuse facility (Windhoek DPR; Lahnsteiner 2018) in order to show the influence of pretreatment, which is more extensive in the latter. This comparison is possible, as the same UF systems (Pentair/Norit/X-Flow Xiga) are employed in all three plants.

Panipat Refinery Water Reclamation Plant

The major design parameters of the blended refinery and petrochemical used water flow (inlet to the reclamation plant) are T = 15–35 °C, 150 mg/l COD, 10 mg/l BOD₅, 10 mg/l oil, 1786 mg/l TDS, and 98 mg/l silica. Basically, the reclamation plant (design capacity = 900 m³/h, 21,600 m³/d) incorporates clarification (including silica adsorption on magnesium hydroxide), pressure sand filtration, ultrafiltration (UF; Fig. 16), and reverse osmosis (RO) phases. The RO permeate is polished by mixed bed ion exchange filters. It is then mainly recycled as boiler make-up water (major target values: TDS < 0.1 mg/L and silica < 0.01 mg/L) in the refinery power plant (see “Panipat Refinery Water Reclamation Plant, Case Study India”).

Chennai Petroleum Water Reclamation Plant

The raw water source consists of secondary effluent from the Kodungaiyur Sewage Treatment Plant. Basically, the reclamation plant (Q = 475 m³/h, 11,400 m³/d) incorporates biological treatment for nitrification and denitrification (sequencing batch reactors), coagulation, precipitation, flocculation, clarification, chlorination (disinfection, removal of residual ammonium), two-stage filtration (pressure sand filtration and multi-media filtration), ultrafiltration, and reverse osmosis. The bulk of the RO permeate is polished by mixed bed ion exchange filters located in the refinery and reused as boiler make-up water in the refinery power plant. The RO permeate is additionally reused as cooling make-up water (see chapter “Advanced Treatment of Municipal Secondary Effluents and Reuse of High-Quality Water in a Refinery and the Automotive Industry, Case Study Chennai/India”).

Windhoek Goreangab Water Reclamation Plant

This globally famous direct potable reuse facility utilizes reclaimed water from domestic secondary effluent, which has been polished in maturation ponds and employs pre-ozonation, coagulation/flocculation, dissolved air flotation, dual media filtration, main ozonation, activated carbon filtration (BAC and GAC), UF, disinfection, and stabilization as process steps (Lahnsteiner 2018). The reclaimed water is pumped directly into the drinking water distribution system, where it is blended with treated dam and borehole water (see chapter “Windhoek/Goreangab Direct Potable Water Reuse, Case Study Namibia”).

UF Design Comparison of the Panipat IOCL, Chennai CPCL, and Windhoek Goreangab WRPs

In order to show how UF design is dependent upon the reuse applications and in particular the influence of pretreatment, the industrial UF designs are compared with that of the Windhoek New Goreangab Water Reclamation Plant, which has a more extensive pretreatment (upstream to the UF; Table 1).

Table 1 Ultrafiltration pretreatment in three different water reclamation plants

The ultrafiltration process steps (at all three facilities) consist of pressure-driven, inside-out, hollow fiber polyether sulfone systems (Pentair/Norit/X-Flow Xiga) and are operated in a dead-end mode. The major tasks of the UF in the industrial WRPs (Panipat and Chennai) are the reduction of the silt density index (SDI) and the removal of turbidity, as well as suspended and colloidal matter, in order to minimize fouling of the downstream reverse osmosis process steps. By contrast, the main objective of the potable reuse UF (Windhoek) is the removal of residual protozoa (cryptosporidia and giardia) and bacteria.

The UF membrane fouling caused by the aforementioned impurities is removed by regular backwashing with permeate. The backwash is enhanced once a day in all three UF plants using chemicals (chemical enhanced backwash – CEB with caustic NaOCl and HCl). As can be seen in Table 2, the Panipat UF was designed for a gross flux of 54 L/(m²∗h), whereas in the Chennai UF, a 22% higher gross flux of 66 L/(m²∗h) is employed. The Panipat UF was designed relatively conservatively, as this industrial application (secondary refinery and petrochemical effluent) was not piloted prior to full-scale realization. Furthermore, the subject membrane was utilized for the first time with this kind of used water, which contains more “difficult” organic compounds (e.g., petrochemical macromolecules) than secondary municipal effluents, and consequently the client requested a safety margin. A degree of full-scale experience with regard to secondary municipal effluent was already available, and therefore a higher flux was applied. The resulting membrane areas are 16,416 m² for the Panipat UF and 7200 m² for the Chennai UF.

Table 2 Comparison of UF designs for different reuse/recycling applications

As shown in Table 2, the flux of the Windhoek UF is substantially higher (102 L/(m²∗h) gross flux) than in the industrial reclamation plants. Indeed, it is nearly twice that of the Chennai system, which uses a similar raw water source. This is explained by the fact that the Windhoek raw water (domestic secondary effluent) is subject to far more extensive pretreatment (additional polishing in maturation ponds, ozone, and activated carbon [BAC and GAC] in the reclamation plant upstream to UF) than that used in the other two sources (Table 1). As might be expected, this indicates that the design of UF processes and membrane lifetime (Table 2) depends greatly upon pretreatment and the resultant UF feedwater quality.

Another issue in UF design is membrane material. Polyvinylidene fluoride (PVDF) is more robust than polyether sulfone (PES) but more expensive. In India, both membranes have been employed in a number of water reclamation plants with good results for both types, e.g., PES in the Indian Oil Corporation Ltd. Panipat Refinery WRP (Fig. 16; Pentair/Norit/X-Flow Xiga) and Reliance Industries Limited (RIL) Jamnagar refinery and petrochemical complex DTA WRP (Fig. 17; Inge Dizzer XL 1.5 MB) and PVDF in the Indian Oil Corporation Ltd. Paradip Refinery WRP (Fig. 18; Toray HFU-2020 N; see chapter “Paradip Refinery Effluent Treatment and Advanced Water Reclamation Plant, Case Study India”). As the market is highly competitive, in the majority of the cases, PES has been used, as this membrane material is cheaper and robust enough to provide appropriate membrane lives (longer than 5 years).

Fig. 17

Reliance Jamnagar refinery and petrochemical complex DTA WRP – Inge PES (Dizzer XL 0.9 MB 70) membrane system. (© WABAG)

Fig. 18

IOCL Paradip Refinery WRP – Toray PVDF (HFU-2020 N) membrane system. (© WABAG)

Pilot Testing

In many cases, pilot tests have to be conducted in order to verify the process design of a full-scale plant or to introduce new technologies such as ceramic membranes or vacuum membrane distillation (see chapter “Distillation in Water and Used Water Purification”). Figure 19 shows a vacuum membrane distillation (VDM) pilot unit, which was used inter alia for TDS concentration in produced water from a Romanian oil field. As previously discussed, pretreatment (removal of oil and total suspended solids) was again decisive for successful operation (TDS was concentrated from 20 to 140 mS/cm) in this case. Pretreatment consisted of an oil separation unit and a dual media filter and provided a substantial removal of TSS (from 40–300 mg/L to less than 10 mg/L) and oil (from 20 volume % to less than 2 mg/L). A membrane autopsy showed that there was low degree and reversible oil fouling, and in order to be on the safe side, an oil inlet concentration of less than 1 mg/L was recommended for full-scale operation.

Fig. 19

Vacuum membrane distillation pilot unit. (© WABAG)

One example of the treatment and reclamation of blended industrial effluents is provided by the pilot testing for the design verification of the Windhoek Ujams Water Reclamation Plant (see chapter “Windhoek/Ujams Industrial Water Reclamation Plant, Case Study Namibia”). The pilot plant consisted basically of micro-sieving (fine-sieving) and MBR treatment (Fig. 20). A key issue in these trials was the COD target value of <45 mg/L (design inlet value 3314 mg/L), which could not be met by biological treatment. The average COD concentration in the MBR permeate was 112 mg/L, and a Zahn-Wellens test demonstrated that the non-biodegradable COD fraction in the used water was higher than expected, and a further biological COD removal (to less than 45 mg/L) was not possible (Proesl et al. 2013). Accordingly, the full-scale design standard was adopted.

Fig. 20

Pilot plant units (micro-sieving and MBR treatment using flat sheet and hollow fiber membranes; from left to right). (© WABAG)

Plant Operation and Maintenance

The plant has to be operated and maintained properly by well-trained and skilled personnel (Fig. 21) from the plant owner or a water treatment specialist (operation and maintenance outsourced). Practice has shown that outsourcing to a specialist, especially in case of advanced water reclamation systems, pays dividends and guarantees reliable process performance and hence a secure water supply.

Fig. 21

Water reclamation plant control room – process supervision. (© WABAG)

Within the context of personnel development, training abroad at other treatment facilities (e.g., MBRs) can be very fruitful, as different experiences and solutions can be discussed and considered at the trainees own plant. Figure 22 shows such training at one of the several European treatment facilities (MBRs) visited. It was organized for process engineers from a developing country, who operate its only advanced industrial water reclamation plant (with an MBR as core technology), and hence it facilitated knowledge transfer from a multi-experienced region to a less experienced country.

Fig. 22

Training of industrial WRP operating personnel (process engineers) at a treatment plant abroad. (© WABAG)

Management of Interconnected Water Treatment Systems

It is advantageous if the entire water management system is in one pair of hands, as in Singapore and Windhoek. Water and used water (wastewater) people normally live in “two different worlds” and therefore communications are very often suboptimal.

In Indian industry, it is frequently the case that two different water technology contractors operate ETPs and water reclamation plants. It would be beneficial if the entire used water and water reclamation management system were operated and monitored by a single experienced water technology specialist, in order to avoid interface losses and subsequently ensure the optimization of the whole system. For example, the performance of the membrane process steps (UF and RO) depends greatly upon the performance of the upstream biological treatment processes, which in winter are regularly disturbed by low wastewater temperatures and occasionally by the inhibiting and/or partly toxic compounds released during the refining and petrochemical processes. It has been recommended that a so-called early warning system (pilot-scale activated sludge plant) be used upstream of the biological treatment plants in order to detect such inhibiting effects in advance. It is further recommended that the entire used water and reclamation management system (“early warning system,” ETPs, and reclamation plants) be operated by only one experienced plant operator with the aim of preventing interface losses and ensuring the optimized performance of the whole system.

Concentrate Management

Concentrate is the higher-concentrated, lower volume stream from a desalination process that contains ions, molecules, and particles separated/removed from feedwater processed to a lower-concentrated, higher volume stream (permeate, condensate, product water). Concentrate management involves the disposal (with or without prior treatment) or beneficial use of this concentrated stream. Frequently, the term concentrate is used synonymously with brine, but this is partially incorrect as brine is a concentrated solution that starts with a dissolved salt content of around 3.5% (a typical concentration of seawater), and therefore concentrate is a more general term, as it also includes the solutions with lower concentrations (< 3.5%) generated during desalination.

Table 3 provides an overview of the concentrate management options, which can be divided between disposal and beneficial reuse. The disposal options are comprised of surface water, sewer discharge, subsurface injection, land application, and evaporation ponds, which as mentioned previously can also be considered as a zero liquid discharge method. The beneficial use options include reuse in industrial processes (such as refinery coke quenching); reuse as service water, oil well injections, and irrigation; and the reuse of high-quality permeate and condensates after high recovery processing (i.e., brine concentration up to zero liquid discharge).

Table 3 Major concentrate management options. (Modified after WateReuse Research Foundation 2013)

Concentrate management is an essential issue, and it would seem that zero liquid discharge (ZLD) is gaining in importance (at least in inland applications). ZLD can be accomplished by employing thermal processes (evaporation and crystallization; see chapter “Zero Liquid Discharge in Industrial Water Reuse and Recycling”) but also by utilizing evaporation ponds. Another ZLD application is the beneficial reuse of the concentrates in industrial processes such as for refinery coke quenching, which is practiced at the inland Panipat Refinery (Haryana State). In this case, the authorities demanded ZLD, as no proper recipient is available in the vicinity of the refinery (see chapter “Panipat Refinery Water Reclamation Plant, Case Study India”). Another inland ZLD facility is the Angul Jindal Steel and Power Coal Gasification Plant (Odisha State), where the RO concentrate is used in the ash handling area for dust suppression (Fig. 23; see also chapter “Angul Jindal Steel and Power Coal Gasification Water Reclamation Plant, Case Study India”).

Fig. 23

Angul Jindal Steel and Power Coal Gasification Plant – ZLD by reusing the RO concentrate in ash handling for dust suppression. (© WABAG)

The brines from high recovery processing and the solids produced in ZLD may either be disposed of or used for the recovery of resources (products). Products can consist of the rare metal gallium or rare-earth metals (such as cerium and neodymium), which among other applications are used in electronics, and salts (such as NaCl, CaSO₄, and CaCO₃), which can be employed directly or as a raw material for further applications (e.g., chlorine-alkali electrolysis). Selective salt recovery represents a potential method of creating valuable products that increase the sustainability of concentrate management. However, for various reasons, feasibility and benefits have yet to be proven in appropriate scale pilot/demonstrations studies (WateReuse Research Foundation 2013).

On coasts, concentrate discharge is normally permitted, but limits have to be met, e.g., for (recalcitrant) COD. At the Paradip Refinery (Odisha State, east coast of India), the design concentrate COD is 250 mg/L, and a standard of 125 mg/L has to be adhered to for sea disposal. The COD is removed by powdered activated carbon adsorption (see chapter “Paradip Refinery Effluent Treatment and Advanced Water Reclamation Plant, Case Study India”). A potentially more cost-effective solution could be the oxidation of the recalcitrant COD by ozone (O₃) in combination with biological treatment units (BIOZONE^® – process by, e.g., MBBR-O₃-MBBR). It is intended to pilot this option in order to prove the technical and economic feasibility. With regard to the technical feasibility, the influence of the high-concentrate total dissolved solids content on the activity of the biomass has to be assessed.

At the Reliance Industries Limited (RIL) Petrochemical Complex at Dahej (Gujarat State, west coast), the RO concentrate is discharged into the Arabian Sea without prior treatment; however a challenging COD limit of 150 mg/L has been set, which requires the extensive removal of this parameter in the upstream biological treatment units (UASB and MBR) (see chapter “Dahej Petro-Chemical Complex Effluent Treatment and Advanced Water Reclamation Plant, Case Study India”). At the second Gujarat RIL refinery and petrochemical complex in Jamnagar (west coast), the RO concentrates (TDS < 3%) from three water reclamation plants (DTA [Fig. 24], C2, and SEZ facilities) are discharged into the Arabian Sea (without prior treatment) together with the higher-concentrated brines (TDS typically 6%) from the seawater desalination units (SWRO and MED).

Fig. 24

RIL refinery and petrochemical complex DTA WRP – reverse osmosis unit. (© WABAG)

Conclusions and Future Directions

Water recycling and reuse solutions have to be economically, technologically, and socially sustainable. These three factors are interlinked and should form the decisive criteria for water management. Economic sustainability cannot only mean short payback periods of 3–5 years. Industry should accept longer return on investment periods in order to promote water reuse and overall sustainability that includes industrial, agricultural, urban, and potable water supply reliability, which is also of great social significance. Social sustainability is important, especially in developing countries and emerging markets, and incorporates the creation of jobs and subsequent improvements in the health situation and the overall standard of living.

Apart from environmental protection and the reliable provision of process and service water, large volumes of freshwater can be saved by industrial water reuse and recycling. This increases the industrial water supply security, which may be endangered due to increased freshwater demands for higher priority agricultural and potable purposes (caused mainly by population growth, urbanization, and climate change). Subsequently, overall water supply management is also facilitated, as additional water is made available.

The motivation for water reuse can simply be OPEX reduction or more strategically the achievement of corporate water and energy sustainability goals (e.g., a 25% reduction in water withdrawal and a 10% reduction in greenhouse gas emissions). The incentives may consist of brand protection and reputational risk minimization, as water can be a constraint upon growth. Furthermore, the water footprint as a measure for sustainability is gaining in importance for the evaluation of listed companies and the subsequent development of their share performance. Government policies such as that in the Indian state Gujarat and private water reuse initiatives will also play an increasing role in the promotion of indispensable water reuse and recycling projects.

The major industrial application consuming the largest quantities of water is thermal power generation, i.e., cooling and steam generation. Cooling and boiler make-up water reclamation requires adequate pretreatment and reverse osmosis in combination with polishing ion exchangers (mixed bed filters) or electrodeionization (EDI). In many cases, RO pass I permeate is used as cooling make-up and pass II permeate as boiler make-up (after polishing in mixed bed ion exchangers). The major objective in boiler make-up water treatment is to avoid corrosion and the formation of deposits. Within this context, the most important quality parameters are pH, conductivity, total dissolved solids, and silica for which, depending upon the boiler type, a stringent value of less than 0.01 mg/L has to be met (after polishing by mixed bed ion exchange). The main problems in cooling circuits are biological growth (including Legionella bacteria), biofouling, corrosion, and scale deposits. Accordingly, typical treatment consists of coagulation/flocculation, lime softening, sedimentation, filtration and disinfection, or alternatively reverse osmosis with appropriate pretreatment and disinfection. For cooling make-up water production, large quantities of relatively low-quality water, which can be reclaimed easily from municipal effluents, are required. As a result, this practice contributes greatly to the saving of freshwater (from public supply) and a subsequent increase in the overall reliability and sustainability of the water supply.

Municipal secondary and (pretreated) industrial effluents represent drought-proof sources for reclamation. The evaluation of water recycling and reuse shows that this practice is technically and economically feasible. Advanced technologies such as membrane filtration are of major significance, especially where the functionality of industrial processes (oil refining, etc.) has to be guaranteed. With this in view, it is also very important that the reclamation plants (consisting of increasingly advanced multiple barrier systems) are operated and monitored by well-trained and skilled personnel from the plant owner or a water technology specialist. Another very important issue is appropriate design (which in many cases is based on pilot tests). Within this context, it must be emphasized that adequate pretreatment (normally by conventional technologies) is decisive for the successful operation of advanced technologies such as membrane filtration and thermal processes. Financing is a further decisive factor in realizing water recycling projects, and innovative, tailor-made financing models will increasingly be employed.

Another crucial success factor is concentrate management, which includes both discharge (with or without prior treatment) into surface waters and beneficial uses (such as the reuse of permeates and condensates after high recovery processing up to zero liquid discharge). Due to the rise in water stress and the tightening of environmental standards, ZLD is gaining in importance, especially in inland applications, and on the coast, sea disposal standards will be steadily implemented. There are numerous research projects relating to the (further) development of technologies/processes for the recovery of valuable resources from brines and the solids produced by evaporation and crystallization. However, it would appear that in most cases, economic feasibility is yet to be accomplished. Nevertheless, this practice has the potential to be successful in the mid-term and would increase the sustainability of industrial water reuse and recycling in a wide range of applications.