Investigation and analysis of college's water system: the case of Northeastern University

Rational and optimal utilization of water resources for sustainable social and economic development is becoming the focus of correlation researches (Hallale, 2002; Gunson et al., 2010).

There has been an increased focus on the water use performance of industrial, regional, and urban areas from a macro-perspective. Most of the initiatives have focused on water quality, for example, purifying sewage (Chen, 2006; Kumar & Pal, 2013). Many have focused on structural optimization, for example, water cycle plans for regional and urban water use (Chen & Chu, 2011; Galvis et al., 2014) or creation of an industrial water use system (Lim et al., 2008; Gao et al., 2011; Žarković et al., 2011). However, only a few research efforts have focused on water reuse systems in schools (Todd et al., 2003; Larsen et al., 2013), and there have been no studies on the structural optimization of water systems in universities and colleges.

Colleges and universities are distinct societies in which water consumption and sewage discharge occur in significant quantities. There are more than 3,000 colleges and universities in China, and there are 35 million employees and students at these institutions. These societies, which include teachers, students, and staff as well as research facilities, have become one of the main sources of water consumption in the urban water system. Unlike industrial sewage, most of the sewage from these institutions is harmless. However, most of the existing studies on campus water consumption only discuss qualitatively the feasibility and benefits of specific water systems.

Northeastern University (NEU) has about 40,000 students and staff, and they consume 4.0 × 10⁶ m³ of water annually. We applied the water extended input–output (WEIO) analysis to quantitatively analyze the water consumption at NEU and to create a complete optimization scheme that can be applicable in populated societies such as other schools and governmental agencies.

Input–output (IO) analysis was used to construct a flow chart and to establish a basic modeling frame for analysis (Leontief, 1936). The analysis is used to trace a substance's migration path regionally or within an economic entity and to explain certain phenomena.

IO analysis is generally applied at the national, provincial, and municipal levels, but is scarcely applied at the campus level. WEIO can be applied at the campus level and reflect the interdependence and feedback effects among architectural elements. In other words, WEIO analysis is applied to study the flow of water and the relationship of water consumption among architectural elements.

Universities have clear partition of function, and different kinds of sewage are classified at the discharge source. Owing to the large water discharge of the campus, there are a number of advantages associated with the management of the pollution control of the water environment and the recycling of the water resource. So, it is necessary to build simple water recycling on campus.

‘Input’ refers to a water resource input to NEU, namely, tap water. ‘Output’ is the total amount of various forms of sewage from daily life, and it is approximately 90% of input. ‘Dissipation’ is the remaining water that dissipates because of evaporation or ground absorption. This water is neither usable nor turned into sewage, and it is approximately 10% of input. The rate refers to a charging scheme for sewage treatment (GB/T, 18920-2002).

In this analytical system, every building is an isolated water point, and different buildings are categorized as ‘sewage resource’ or ‘recycled water use’ based on their water consumption and emission features (see the two types presented in Figure 1). A sewage resource acts as a source of applicable drainage, which is output from the buildings. Recycled water use acts as a source of recycled water, which is input into the buildings. A reuse water point should have at least one of the above-mentioned features, i.e., it can be a sewage resource building, a recycled water use building, or both.

In an optimized system, water consumption is significantly improved. The fact that the majority of sewage is reused contributes to reduce per capita water consumption and per capita water discharge, and alleviate the impact of sewage on the environment, and it also reduces the cost of waste-water treatment. Thus, the optimized system can play a major role in water recycling, water-saving and emission-reduction.

The buildings at NEU are not equipped with independent water meters, so we cannot obtain monthly water reports for each building. Thus, the related statistics are mainly from field investigations and observations.

School buildings are closed during summer and winter holidays; thus, the population is reduced dramatically. Therefore, we consider the days in which water is used as D = 270 days in a year. Table 1 shows that even the most polluted dormitory sewage is of an acceptable quality and can meet the ‘Miscellaneous Urban Water Quality Standard’ (GB/T, 18920-2002). This sewage can be reused after simple treatment.

In NEU, the sewage resource (output) units are as follows (see Figure 4):

1. T: Dacheng building (D), Heshili building (H), Yifu building (Y), Jidian building (J), Yejin building (E), Library (L), Jianzhu building (A), Caikuang building (C). Because school-run factories, key labs, and integrated office buildings have a small staff, fewer users, inaccessible valid water use data, and are significantly affected by the type of experiments being performed, the water consumption from these facilities was not taken into consideration.

2. D: 1st, 2nd, and 8th dining halls, central dining hall, rice-purchasing station, and Hui restaurant (lower water-consuming canteens are ignored, namely, Peixun canteen and NEU Gourmet Café).

3. B: NEU bath house has a water meter that provides data directly.

4. A: 1st–9th dormitory and Peixun dormitory. (The living conditions of postgraduate students are similar to those of undergraduate students; all the students were given a sampling survey so that we could collect daily water consumption data from both male and female students.)

Recycled water use (input) units are as follows:

1. S: 1. School buildings—Dacheng building (D), Heshili building (H), Yifu building (Y), Jidian building (J), Yejin building (E), Library (L), Jianzhu building (A), and Caikuang building (C). 2. Student apartments—1st–9th dormitory and Peixun dormitory.

2. F: 1. School buildings—Dacheng building (D), Heshili building (H), Yifu building (Y), Jidian building (J), Yejin building (E), Library (L), Jianzhu building (A), and Caikuang building (C). 2. Student apartments—1st–9th dormitory and Peixun dormitory.

3. P: Fire protection tanks.

4. G: NEU gardening center.

5. A: Artificial pools.

Sewage resource is ‘Output,’ i.e., applicable sewage. We presume Output accounts for 90% of the total drainage because of evaporation or other reasons. Thus, we induce the ratio R = 90%.

The results from the above calculation enable us to identify a pattern of water consumption at NEU (see Figure 5). All of the statistics in this figure can be found in the Appendix (available in the online version of this paper). This will illustrate the consumption ability of a building and the differences among various kinds of buildings.

This open and unidirectional pattern of intake → delivery → consumer's → emission at NEU, is required to be transformed into a feedback–recycle process of intake within measure → delivery → consumer's → water reuse → consumers, enabling a continuous recycling of water on campus.

The following measures and suggestions should be taken into consideration:

1. Add simple filters and disinfection device during the process from sewage resource to recycled water use so that large-particle suspended matter in the sewage is removed and sewage is deodorized and disinfected.

2. For water systems containing both sewage resources and recycled water use sectors, we can consider a near arrangement of single building recycling to reduce costs of pipes.

3. We also recommend a directional water supply system. For example, sewage from the bath house can be directionally used in a gardening center after simple treatment, forming an independently adjustable circulatory system with a lower cost of pipes and of constructing a control center.

After completion of the optimized system, the gardening center will be able to receive 40% of its water supply from canteens, the organics in canteen sewage can also benefit vegetation growth, 100% of washroom sewage from dormitories can be reused, and the bath house sewage can be reused entirely after a simple cooling and filtering treatment. We can observe a significant decrease in water consumption and discharge per capita, which reduce from 106.72 m³/year and 96.04 m³/year to 92.13 m³/year and 86.65 m³/year, respectively. In addition, the volume of sewage is higher than that of recycled water, so there will be no issues regarding storage, over treated sewage, or energy waste.

Buildings can be categorized according to their water cycle function as either sewage resource or recycled water use points. An investigation was performed on water quality and quantity, including the reallocation of water resources to strengthen the relationship between sewage resource and recycled water use. It was shown that reducing the total water consumption and per capita water consumption to a significant extent results in a reduction in water cost of about 780,000 yuan annually.

A universal concept was summarized for water system optimization based on the analytical and optimizing processes at NEU. This concept is not limited to higher education institutions and can be applied in other societies and enterprises. If these optimization measures are adopted at all the colleges in the northeastern region of China, 970.80 × 10⁵ m³/year of water can be saved, which is equivalent to 42.72 million yuan. If the measures are adopted in higher education institutions all over the country, 7,842.77 × 10⁵ m³/year of water can be saved, which is equivalent to 345 million yuan. Therefore, if these optimization measures could be taken in the water system of colleges and universities, we could substantially increase the amount of reused water and reduce daily water emissions.

The authors are grateful for the financial support provided by the National Natural Science Foundation of China (No. 41301643, 71373003, 41401636), the Public Projects of the Ministry of Environmental Protection (No. 201009063), the Projects of Normal University (N110702001), National Water Pollution and Management (2012ZX07202-001-003), and Soft Topic of Province Plan Project (142400410263).